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What is Viagra used for? Viagra is used to treat impotence in men. Viagra increases the body’s ability to achieve and maintain an erection during sexual stimulation. Viagra does not protect you from getting sexually transmitted diseases, including HIV. take Viagra? Men who are currently using medicines that contain nitrates, such as nitroglycerin should not use Viagra because taken together they can lower the blood pressure too much. Viagra should not be used by women or children. In patients taking Viagra, several heart-related side effects have been reported, including heart attack, sudden death, irregular heart rhythm, stroke, chest pain, and increased blood pressure. It is not possible to determine whether these events are directly related to Viagra, to sexual activity, to the patient’s heart condition, to a combination of these factors, or to other factors. taking certain medications at the same time (e.g., ketoconazole, itraconazole, erythromycin and saquinavir). In these patients, the recommended starting dose of Viagra is 25 mg. Heart attack, stroke, or life-threatening irregular heart rhythm within the last 6 months Because Viagra lowers blood pressure, your doctor will evaluate your overall medical condition to determine if Viagra, in combination with sexual activity, could adversely affect you. Viagra can cause a rare but serious condition of prolonged erection (priapism). It is important to contact your health care provider immediately if your erection lasts longer than 4 hours. Men for whom sexual activity is inadvisable may not be good candidates for Viagra. Tell your doctor if you are taking protease inhibitors for the treatment of HIV. You should have a complete medical history and exam to determine the cause of your impotence before taking Viagra. Men who have medical conditions that may cause a sustained erection such as sickle cell anemia, leukemia or multiple myeloma or who have an abnormally shaped penis may not be able to take Viagra. There are several medications that are known to interact with Viagra, so be sure to tell your doctor about all medications you are taking including those you can get without a prescription. Viagra has not been studied with other treatments for impotence, so use in combination with other treatments is not recommended. What are some possible side effects of Viagra? a complete list of side effects reported with Viagra. Your health care provider can discuss with you a more complete list of side effects.) ). The following is a listing of the most common side effects Visual changes such as mild and temporary changes in blue/green colors or increased sensitivity to light. For more detailed information about Viagra, ask your health care provider.

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Message copied & clipped from an e-mail we recieved from a more than happy customer. Wow what can I say… an amazing experience. In August a couple of my friends and I had planned to go on a short break to Amsterdam to unwind from stress and worries of our normal lives. We already had lots of things planned to do while we were there but once we arrived we were suprised to see one of our mates had brought along ). I personally hadn’t tried this stuff before, but I was always anxious when joining a female in the ‘bedroom department’ just incase I under performed so the thought of buying viagra or a viagra alternative had always crossed my mind but I just simply didn’t get around to it. This made me quite excited to use it. On the second night of being there, our mate suggested for us to go to a strip bar and as you can imagine we hit bar after bar and ended up in you know where. My mate pulled out the strip of kamagra jellys and we got down to business! My friend who brought the kamagra originally gave me your website address so I could buy some more at a later date. So I decided to e-mail you guys with a short story of my experience of generic viagra. Oh and yes, the sex was amazing!

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Jetlag is defined as a temporary disturbance of the bodily rhythms which is caused by high-speed travel, whether it is on land or on air and across various time zone. This disturbance is usually common in jet aircrafts. People who cross various time zones find it easier to recover from jet lag if the purpose of the travel is for a vacation. This is because when a person travels to a place where he is allowed to relax and recover slowly, it gives him the chance to adjust to the local time of the area. But there are also persons who are not that lucky. People who travel for business purposes usually cross a lot of time zones. When the business traveler reaches his destination he gets busy attending meetings and doing the work that has to be done all based on the local time of that certain place. Thus the business travelers cannot afford the luxury of relaxing and adjusting their bodies to the place's local time. Can Viagra be a relief for jetlag? It is usually not known that there is a certain link between Jetlag and Viagra. A recent study has shown that not only does Viagra treat erectile dysfunction but it can actually also neutralize the effects of jetlag. Viagra has been observed to restore normal bodily clock functions which have been shifted by six hours. Viagra was first developed by Pfizer for aid in treatment of angina and high blood pressure by disturbing the enzyme that causes the reduction of cGMP, a natural compound, cGMP plays a very important in the function of penile erection. In relation to jetlag, cGMP acts in a region of the brain whose role is to regulate the circadian cycle. The circadian cycle is the body's internal clock that determines the waning and the waxing of hormones and also controls the urge to sleep and wake. In a laboratory test, hamsters were injected with Viagra and subjected to bright lights for 6 hours ahead of the regular time. They were observed by a team of researchers from the Universidad Nacional de Quilmes. They found that the injected hamsters have improved in coping with the time difference by 25 to 50 percent as those compared to the hamsters that were not administered with Viagra. The testing gave out a positive result in the light to dark cycle which is the equivalent of traveling from west to east. Further test is needed to really identify the possibility of Viagra as an effective treatment to counter the ill feeling of traveler's jetlag. If this can be validated, then the blue pill can cross the barrier of time and human dysfunction. indian sildenafil When we speak of sex drive problems, or dysfunction, we automatically think of males and erectile dysfunction, and omit women from the equation. However, many women experience problems with their â€?libido' or sexual energy, and this phenomena deserves attention too. Viagra is the most common treatment for erectile dysfunction in males, and has traditionally been recommended for men only, women being advised not to use it. So the main reason for this is lack of empirical research stating otherwise, which is due to the absence of definitive studies on women. Viagra however can work for women, as it increases the blood flow to a woman's genitals (much the same way as with a man's), which boosts their libido. There are important considerations however, which shall be listed below. As Viagra is aimed at men's erectile dysfunction, women are unable to obtain a prescription and buy Viagra from a pharmaceutical store. However generic versions are available on the internet, but as so many are on the market, if in doubt contact the supplier as to whether a product is available. When buying from online pharmacies, it is possible to check their pharmacy ID if concerned about legitimacy. It is important for women to take into consideration possible side effects of Viagra, although not widespread there is still a possibility of them occurring. For instance, some Viagra users have reported dizziness, flushing, loss of vision, and so on. Check all possible side effects before commencing use. Furthermore, Viagra should not be taken alongside any nitrate medicines as this can cause abnormally low blood pressure, so always check! Women, who suffer with a low sex drive often, should seek a long term cure other then Viagra in order to increase their libido and have a permanent effect. Long term Viagra use can result in expense, so if the problem continues regularly, even after Viagra use, women should aim to seek other remedial methods. mexican sildenafil HE is only two, but Oliver Sherwood regularly takes Viagra - to keep him alive. The toddler has a rare condition that causes chronic high blood pressure. Something as simple a chest infection could kill him. The pulmonary hypertension, as it is known, can be controlled with four doses of Viagra a day. The drug improves blood flow, which in adults can boost erectile function but in rare cases such as Oliver's can open the veins and capillaries to aid circulation. His mother Sarah, a part-time nurse, said: "We joke when we pick up his drugs that it would be Christmas come early for most people. Obviously the dose isn't high enough to have the effect it would on adults. "Viagra is an expensive drug but it's actually one of the cheapest to treat pulmonary hypertension. "We're just hoping it'll continue to work as he grows a bit older." But Oliver's future could be in doubt because other drugs he could use as he gets older might no longer be funded by the Health Service. Pulmonary hypertension causes the blood pressure in the arteries in the lungs to rise, straining the heart and reducing blood oxygen levels, causing breathlessness and exhaustion. Symptoms include severe coughing and breathing problems as blood fills the lungs, constant nose bleeds, dizziness and chest pains. The condition, which affects 4,000 in Britain, often leads to heart failure. It is so rare that only five children a year are diagnosed with it in the UK. The survival rate is around five years, even with medication such as Oliver, who cannot walk more than a few steps without getting out of breath, takes one tablet of Sildenafil crushed into four 5ml doses a day. Doctors can increase the dose when his condition worsens, but there is no way of telling how much longer the drugs will be effective. As he grows up he will need to switch to more expensive treatments called Epoprostenol and Iloprost to control his condition. But the Government's drug rationing agency, the National Institute for Health and Clinical Excellence, is considering whether to continue prescribing them. Oliver's mother has started a petition calling for the Health Service to keep funding the treatments. Mrs Sherwood, 34, of Hucclecote, Gloucestershire, said: "The only hope we had was that he would be maintained through medication but if anything-happens in the future that hope may be taken away." The Pulmonary Hypertension Association said: "The clinical evidence for this is unfounded and it must be assumed it is based on cost alone." A spokesman for NICE added: "Our review of the evidence suggests that Sildenafil is both clinically effective and cost-effective in treating pulmonary arterial hypertension." compare levitra cialis versus viagra Viagra is one of the few prescription drugs that require almost no publicity. You can find news stories, detailed description and jokes in print, on television and on the internet. Sexual dysfunction is a very serious issue for those who are suffering as well as for their partners. After years without the ability to enjoy sexual intimacy, it is no surprise that lots of people all over the globe are ready to try Viagra. Though the drug that is capable of restoring penile erectile functions, it has wide array of medical, economic and social problems attached. Older users with severe heart disease may experience side effects which can lead to death and the chemical effects of Viagra are also life threatening. Additionally, adverse social effects of Viagra use have also come into the fray in various media circles. There are newspaper reports that say the lives of older couples are being ruined because of Viagra. Men are leaving longstanding relationships for younger women and there are cases of assault on women because of their lack of response to a partner’s new sexual routine. The normal dose of Viagra is 50 mg taken about an hour prior to the expected sex act, though the medication is effective even if taken four hours prior to sex. It is of paramount importance that the next dose not be used until after a day has passed from the last intake. Most importantly, patients with liver or kidney disease should take lower dosages (25 mg) due to their lower ability to eliminate the drug. The most basic reactions with the use of Viagra are headaches, flushing, indigestion and nasal congestion. These sorts of reactions occur in 4% - 16% of patients taking Viagra. Most of the adverse reactions are mild in nature and quite well handled by healthy individuals. While it cannot be termed as an adverse reaction, the new-found sexual prowess can lead older males with underlying medical issues such as heart disease to exert themselves more than they have in recent years. This can precipitate a heart attack or other acute medical emergency. According to one study, the Food and Drug Administration has reported sixteen deaths that followed the use of Viagra. All of these deaths occurred in individuals sixty years and older suffering from of heart disease, hypertension or diabetes. The use of Viagra may lead to stress and marital discord which can result in divorce and the need for psychological counseling. Apart from that, the enhanced sexual routine may also give rise to sexually transmitted diseases and AIDS in older individuals who would not normally be exposed.

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Viagra turns 10 this month, and didn't time just fly? It seems like only yesterday we started guffawing at the Symbolism for Dummies ads on TV for the little blue pill and its "erectile dysfunction" rivals -- footballs tossed through tires, faucets erupting. The spots ended with a list of potential side effects that sounded like a satire of potential side effects. "More than four hours?" we winced. "Ouch." However discomfiting the commercials, the Food and Drug Administration (FDA) approval of Viagra -- on March 27, 1998 -- is a landmark day in the history of sex. It seemed at the time like a biomedical revolution was upon us all, and about five minutes after word of the magical med went global, the question first was asked: Where is the women's version of Viagra? The short answer: They're still working on it. A bunch of companies have tried and failed to create "pink Viagra," as it's often called. Other companies have drugs in late stages of clinical testing, including a gel that recently began a make-or-break nationwide study with several thousand women. Give us five years, maybe less, say the most optimistic researchers and doctors. Though it's unclear exactly how many women would ask for a prescription, no one doubts that the first company that gets to market a remedy for female sexual dysfunction (FSD), as it's formally known, will earn a fortune. But as this race reaches what could be its final lap, not all of the spectators are cheering. Some, in fact, are booing as loudly as they can. A modest-size but fervent group of psychologists, academics and public health advocates contend that FSD isn't an authentic medical condition, or at least not the sort of problem that should be treated with drugs. These aren't the obtuse male physicians who for decades have been telling women distressed by their lack of libido that "it's all in your head." The anti-FSD crowd is mostly women, many of them self-described feminists. The most prominent is Leonore Tiefer, a psychotherapist and clinical associate professor at New York University, who has long decried what she calls "the medicalization of women's sexuality." "Drug companies want to say to women, 'You don't need to know anything; you can have the satisfying sex life that you seek -- people dancing on TV, the whole bit -- without knowing anything. Just ask your doctor,' " she says. "I resent that, because there are specific harms that come from being ignorant and dependent in the world we live in. There may be lots of people who aren't interested in sex, but is there a medical reason for that, and do we diagnose that?"

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Sildenafil Tablets 25 mg, 50 mg, 100 mg (sil-DEN-a-fil) Treating erectile dysfunction (ED). It may also be used for other conditions as determined by your doctor. Viagra is a phosphodiesterase inhibitor. It works by helping to increase blood flow into the penis during sexual stimulation. This helps you to achieve and maintain an erection. you are taking nitrates (eg, isosorbide, nitroglycerin) in any form (eg, tablet, capsule, patch, ointment) or nitroprusside you use certain recreational drugs called "poppers" (eg, amyl nitrate, butyl nitrate) Contact your doctor or health care provider right away if any of these apply to you. Some medical conditions may interact with Viagra . Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you: if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement if you have allergies to medicines, foods, or other substances if you have a deformed penis (eg, Peyronie disease, cavernosal fibrosis), blood problems (eg, sickle cell anemia, leukemia, multiple myeloma), or any other condition that may increase the risk of a prolonged erection (eg, priapism) if you have a history of certain eye problems (eg, retinitis pigmentosa, sudden vision loss, optic neuropathy, macular degeneration) if you have a history of liver or kidney problems, high or low blood pressure, ulcers, bleeding problems, heart problems (eg, heart failure, irregular heartbeat, aortic stenosis, angina), or blood vessel problems if you have a history of heart attack, stroke, or life-threatening irregular heartbeat, especially within the past 6 months Some MEDICINES MAY INTERACT with Viagra . Tell your health care provider if you are taking any other medicines, especially any of the following: Alpha-blockers (eg, doxazosin), amlodipine, medicines for high blood pressure, nitrates (eg, isosorbide, nitroglycerin), or nitroprusside because severe low blood pressure with dizziness, lightheadedness, and fainting may occur Azole antifungals (eg, itraconazole), cimetidine, H2 agonists (eg, famotidine), HIV protease inhibitors (eg, ritonavir), macrolide antibiotics (eg, erythromycin), or telithromycin because they may increase the risk of Viagra 's side effects This may not be a complete list of all interactions that may occur. Ask your health care provider if Viagra may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine. Use Viagra as directed by your doctor. Check the label on the medicine for exact dosing instructions. An extra patient leaflet is available with Viagra . Talk to your pharmacist if you have questions about this information. Take Viagra by mouth with or without food. Viagra may not work as quickly if you take it with a high-fat meal. Viagra is usually taken about 1 hour before sexual activity. However, it may be taken anywhere from 4 hours to ? hour before sexual activity. Talk with your doctor about the best way to take Viagra . Do not take Viagra more often than once daily, or as directed by your doctor. If you miss a dose of Viagra and you still intend to engage in sexual activity, take it as soon as you remember. Continue to take it as directed by your doctor. Ask your health care provider any questions you may have about how to use Viagra . Viagra may cause dizziness, drowsiness, fainting, or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Viagra with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it. Viagra may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects. Patients with heart problems who take Viagra may be at increased risk for heart-related side effects, including heart attack or stroke. Symptoms of a heart attack may include chest, shoulder, neck, or jaw pain; numbness of an arm or leg; severe dizziness, headache, nausea, stomach pain, or vomiting; fainting; or vision changes. Symptoms of a stroke may include confusion, vision or speech changes, one-sided weakness, or fainting. Contact your doctor or seek medical attention right away if you experience these symptoms. Viagra may rarely cause a prolonged, painful erection. This could happen even when you are not having sex. If this is not treated right away, it could lead to permanent sexual problems such as impotence. Contact your doctor right away if this happens. Do not use other medicines or treatments for erectile dysfunction while you are taking Viagra . Viagra does not stop the spread of HIV or other sexually transmitted diseases (STDs) to others through sexual contact. Use barrier methods of birth control (eg, condoms) if you have HIV infection or an STD. Viagra will not prevent pregnancy. If your partner may become pregnant and you wish to avoid pregnancy, be sure to use an effective form of birth control. Use Viagra with caution in the ELDERLY; they may be more sensitive to its effects. Viagra is not recommended for use in CHILDREN; safety and effectiveness in children have not been confirmed. PREGNANCY and BREAST-FEEDING: Viagra is not approved for use in women. If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Viagra while you are pregnant. It is not known if Viagra is found in breast milk. If you are or will be breast-feeding while you use Viagra , check with your doctor. Discuss any possible risks to your baby. All medicines may cause side effects, but many people have no, or minor, side effects. Diarrhea; dizziness; flushing; headache; heartburn; mild, temporary vision changes (eg, blurred vision, sensitivity to light, blue/green color tint to vision); stuffy nose; upset stomach. Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fainting; fast or irregular heartbeat; painful or prolonged erection; ringing in the ears; seizure; severe or persistent dizziness; severe or persistent vision changes; sudden decrease or loss of vision in one or both eyes; sudden hearing loss. This is not a complete list of all side effects that may occur. If you have questions or need medical advice about side effects, contact your doctor or health care provider. You may report side effects to the FDA at 1-800-FDA-1088 (1-800-332-1088) or at . Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center ( ), or emergency room immediately. Symptoms may include chest pain; fainting; prolonged erection; severe dizziness. Store Viagra at 77 degrees F (25 degrees C). Brief storage at temperatures between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Store away from heat, moisture, and light. Do not store in the bathroom. Keep Viagra out of the reach of children and away from pets. If you have any questions about Viagra , please talk with your doctor, pharmacist, or other health care provider. Viagra is to be used only by the patient for whom it is prescribed. Do not share it with other people. If your symptoms do not improve or if they become worse, check with your doctor. This information is a summary only. It does not contain all information about Viagra . 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This is a summary of the most important information about Viagra. For details, talk to your healthcare professional. FDA ALERT [7/2005]: A small number of men have lost eyesight in one eye some time after taking Viagra, Cialis, or Levitra. This type of vision loss is called non-arteritic anterior ischemic optic neuropathy (NAION). NAION causes a sudden loss of eyesight because blood flow is blocked to the optic nerve. We do not know at this time if Viagra, Cialis, or Levitra causes NAION. NAION also happens in men who do not take these medicines. People who have a higher chance for NAION include those who: FDA has approved new labels for Viagra, Cialis, and Levitra to include information on possible eyesight loss (NAION). Stop using Viagra, Cialis, or Levitra if you have a loss in your eyesight. Get medical help right away. This information reflects FDA's current analysis of data available to FDA concerning this drug. FDA intends to update this sheet when additional information or analyses become available. What is Viagra? Viagra is a prescription medicine taken by mouth for the treatment of erectile dysfunction (ED) in men. ED is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. Viagra may help a man with ED get and keep an erection when he is sexually excited. Viagra must be used only under a doctor's care. protect a man or his partner from sexually transmitted diseases, including HIV. Speak to your healthcare professional about ways to guard against sexually transmitted diseases. Viagra is only for men with ED. Viagra is not for women or children. Viagra must be used only under a healthcare professional's care. Who Should Not Take Viagra? What are The Risks? The following are the major possible risks and side effects of Viagra therapy. This list is not complete. Viagra can cause your blood pressure to drop suddenly to an unsafe level if it is taken with certain other medicines such as nitrates and alpha-blockers, and recreational drugs that contain nitrates called "poppers". A sudden drop in your blood pressure could cause you to become dizzy, faint, or have a heart attack or stroke. Tell all your healthcare professionals that you take Viagra. If you need emergency medical care for a heart problem, it will be important for your healthcare professionals to know when you last took Viagra. vision changes, such as seeing a blue tinge to objects or having difficulty telling the difference between the colors blue and green What Should I Tell My Healthcare Professional? have retinitis pigmentosa, a rare genetic (runs in families) eye disease have blood cell problems such as sickle cell anemia, multiple myeloma, or leukemia Can Other Medicines or Food Affect Viagra? Viagra and certain other medicines can interact with each other. Tell your healthcare professional about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Know the medicines you take. Keep a list of them with you to show your healthcare professional. Date created: July 8, 2005, updated October 2, 2007.
Erectile dysfunction in men is a common problem, even more so in men over the age of 45. different lifestyle traits can contribute to erectile dysfunction, however viagra is the most commonly used cure for impotence and erectile dysfunction. it is not necessarily the case that men naturally experience a lower sexual drive or erectile dysfunction when they reach a certain age. a man's inability to gain and sustain an erection may be due more to abnormalities in treatable physical conditions. in 1983, dr giles brindley made the discovery and demonstrated that a penis could be made erect by injecting it with the drug phentolamine. he discovered the penis could be mad erect by relaxing the normally constricted blood vessels. once the vessels are relaxed, they let increased blood into the penis, which then inflates to form an erection. two problems however were soon recognised. phentolamine is not selective enough to target only the penis to inflate and can unpredictably effect other parts of the body. secondly, the erection is not brought on by sexual stimulation and a man will continue to have an erection until the drug wears off. viagra combats such drawbacks however. it works by enhancing the natural process that occurs when a man is sexually stimulated. viagra controls what we might call â�?softeners'- chemicals in the body designed to make the penis soften after an erection has occurred. when a man is sexually stimulated chemicals in the body relax the blood vessels in his penis and increase the blood flow. at the same time the body also produces phosphodiesterase (pde5), which work to subside the erection afterwards. erectile dysfunction is an imbalance which results in the inability of a male to sustain an erection. viagra reduced such â�?softeners', allowing blood flow to the penis to create sustainable erections. viagra does not take the place of stimulation but increases the effects of stimulation. after the viagra has worn off (usually 4 or 5 hours later), the normal processes are restored to how they were prior to taking viagra. possible side effects can occur, such as flushing and dizziness, and if an individual experiences these, they should consult a doctor. A Revolution of any sort brings with it a new way a life. Viagra, the little blue bill developed for the treatment of erectile dysfunction (ED) has led to a new sexual revolution. This sexual revolution has brought with it a radical change in terms of sexual morality as well as behaviour all around the globe. This is not just another drug; it is the magic bullet that people have been waiting a long time for. Blame it on their nature, men are whimsical creatures who have big egos more and adjudicate their performance on the basis of their sexual prowess. That is where, when men loose their control over sexual ability, they tend to lose their self control. If a man is suffering from ED he is not going to discuss his sex life with anyone, not even with his health care provider. He may even feel embarrassed to talk about it with his mate. Thanks to Viagra, impotence is no longer a taboo issue. Believe it or not, men are coming up openly to discuss and correct their sexual ailment. The sexual revolution attached with Viagra has changed the whole attitude of men’s towards sexuality. With the assistance of Viagra, men are confident that they can satisfy their partner with ease. All in all, their sexual behavior has become more progressive and adventurous. Viagra can restore virility in about 80% of men who have issues, with only minor side effects such as headaches and indigestion. Older medical treatments can leave men with erections that last for more than four hours if sex does not take place. The best part about Viagra is that it only becomes effective when a man is sexually aroused. The drug start making its presence felt when it blocks the operation of an enzyme that plays a prominent role in breaking down the chemical cyclic GMP which is quite important in maintaining erections. Normally, Viagra assisted erections subside after intercourse, a few men have reported that the drug can remain effective for a day. There is no denying that Viagra is fulfilling the requirements of millions of men all around the globe who are suffering from erectile dysfunction by offering them an opportunity to regain their sex lives and lighten up their low self esteem. It assists in infusing freshness in a stale relationship, is a ray of hope for millions of sexually dissatisfied people and has the ability to redefine the meaning of sex and sexuality in your mind and body.  generic viagra online pharmacy Why is Viagra prescribed? Viagra is an oral drug for male impotence, also known as erectile dysfunction (ED). It works by dilating blood vessels in the penis, allowing the inflow of blood needed for an erection. Viagra causes erections only during sexual excitement. It does not work in the absence of arousal. How should you take Viagra? Taking Viagra approximately 1 hour before sexual activity works best for most men. Depending on how and when the drug works for you, an interval of one-half hour to as much as 4 hours may prove ideal. --If you miss a dose... for regular use. Take it only before sexual activity. --Storage instructions... Store at room temperature. What side effects may occur? Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking Viagra. Abnormal vision (color tinge, blurring, sensitivity to light), acid indigestion, diarrhea, flushing, headache, nasal congestion, urinary tract infection Heart attack, stroke, heart irregularities, dangerous surges in blood pressure, and sudden death have all been reported after use of Viagra, usually in men with existing cardiac risk factors, and typically during or shortly after sex. Why should Viagra not be prescribed? Do not take Viagra if you are taking any nitrate-based drug, including nitroglycerin patches (Nitro-Dur, Transderm-Nitro), nitroglycerin ointment (Nitro-Bid, Nitrol), nitroglycerin pills (Nitro-Bid, Nitrostat), and isosorbide pills (Dilatrate-SR, Isordil, Sorbitrate). Combining Viagra with these drugs can cause a severe drop in blood pressure. If Viagra gives you an allergic reaction, do not use it again. If you have heart problems severe enough to make sexual activity a danger, you should avoid using Viagra. Use it cautiously--if at all--if you've had a heart attack, stroke, or life-threatening heart irregularities within the past 6 months. Be equally cautious if you have severe high or low blood pressure, heart failure, or unstable angina (crushing heart pain that occurs at any time). If you take Viagra and develop cardiac symptoms (for example, dizziness, nausea, and chest pain) during sexual activity, do not continue. Alert your doctor to the problem as soon as possible. If you have a condition that might result in long-lasting erections, such as sickle cell anemia, multiple myeloma (a disease of the bone marrow), or leukemia, use Viagra with caution. Also use cautiously if you have a genital problem or deformity such as Peyronie's disease. If an erection lasts more than 4 hours, seek treatment immediately. Permanent damage and impotence could result. If you have a bleeding disorder, a stomach ulcer, or the inherited eye condition known as retinitis pigmentosa, use Viagra with caution. Its safety under these circumstances has not yet been studied. To avoid low blood pressure, do not take the 50-milligram or 100-milligram dose of Viagra within 4 hours of taking an alpha-blocking drug such as Cardura. Remember that Viagra offers no protection from transmission of sexually transmitted diseases, such as HIV, the virus that causes AIDS. If Viagra is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining Viagra with the following: Erythromycin (E-Mycin, Ery-Tab, PCE) Nitrates such as Isordil, Nitro-Bid, and Nitro-Dur Rifampin (Rifadin, Rimactane) Saquinavir (Fortovase, Invirase) Viagra should not be used by women. Its affects during pregnancy and breastfeeding have not been studied. Doses range from 25 milligrams to 100 milligrams, depending on the drug's effect. The usual dose is 50 milligrams. If you are over 65, have liver or kidney problems, or are taking erythromycin, ketoconazole, itraconazole, ritonavir, or saquinavir a dose of 25 milligrams may be sufficient. Your doctor will adjust the dosage if the drug is not working properly for you. Take Viagra only before sexual activity. The manufacturer recommends a maximum of 1 dose per day (1 dose every 2 days for those taking ritonavir). To avoid low blood pressure, do not take the 50-milligram or 100-milligram dose of Viagra within 4 hours of taking an alpha-blocking drug such as Cardura. No overdose of Viagra has been reported. However, any medication taken in excess can have serious consequences. If you suspect an overdose, seek medical attention immediately. viagra price online The latest alert was prompted by a case report in the Journal of Laryngology & Otology of sudden hearing loss in a man taking Viagra. A search of FDA records found 29 similar reports involving ED drug users and a few people who took the drugs during clinical trials. Although hearing loss is common in men in their 50s -- the age group most likely to take ED drugs -- age-related loss tends to be gradual, unlike the kind tied to the warning. The FDA has also issued a hearing-loss warning on Revatio, a blood pressure drug in the same class. Revatio users who experience hearing problems should stay on the drug until they have checked with their doctor. ED drugs, on the market for more than a decade, generally have an excellent safety record. More-common problems include flushing and muscle soreness. sildenafil buy viagra cialis china shanghai no prescription Are you really positive that ED (erectile dysfunction) is having an effect on your sexual health? Or are you unsure if you have ED? Pfizer have a test for you to take on their website which holds five very important questions to ask yourself. This test only takes two minutes of your time, and may provide you with some good answers. To take the test, head over to and rate your sexual health today. 5 sildenafil citrate canada What is Viagra used for? Viagra is used to treat impotence in men. Viagra increases the body’s ability to achieve and maintain an erection during sexual stimulation. Viagra does not protect you from getting sexually transmitted diseases, including HIV. take Viagra? Men who are currently using medicines that contain nitrates, such as nitroglycerin should not use Viagra because taken together they can lower the blood pressure too much. Viagra should not be used by women or children. In patients taking Viagra, several heart-related side effects have been reported, including heart attack, sudden death, irregular heart rhythm, stroke, chest pain, and increased blood pressure. It is not possible to determine whether these events are directly related to Viagra, to sexual activity, to the patient’s heart condition, to a combination of these factors, or to other factors. taking certain medications at the same time (e.g., ketoconazole, itraconazole, erythromycin and saquinavir). In these patients, the recommended starting dose of Viagra is 25 mg. Heart attack, stroke, or life-threatening irregular heart rhythm within the last 6 months Because Viagra lowers blood pressure, your doctor will evaluate your overall medical condition to determine if Viagra, in combination with sexual activity, could adversely affect you. Viagra can cause a rare but serious condition of prolonged erection (priapism). It is important to contact your health care provider immediately if your erection lasts longer than 4 hours. Men for whom sexual activity is inadvisable may not be good candidates for Viagra. Tell your doctor if you are taking protease inhibitors for the treatment of HIV. You should have a complete medical history and exam to determine the cause of your impotence before taking Viagra. Men who have medical conditions that may cause a sustained erection such as sickle cell anemia, leukemia or multiple myeloma or who have an abnormally shaped penis may not be able to take Viagra. There are several medications that are known to interact with Viagra, so be sure to tell your doctor about all medications you are taking including those you can get without a prescription. Viagra has not been studied with other treatments for impotence, so use in combination with other treatments is not recommended. What are some possible side effects of Viagra? a complete list of side effects reported with Viagra. Your health care provider can discuss with you a more complete list of side effects.) ). The following is a listing of the most common side effects Visual changes such as mild and temporary changes in blue/green colors or increased sensitivity to light. For more detailed information about Viagra, ask your health care provider. Revatio, Viagra What is Viagra? Viagra relaxes muscles and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women. Viagra may also be used for other purposes not listed in this medication guide. Do not take Viagra if you are also using a nitrate drug for chest pain or heart problems. This includes nitroglycerin (Nitrostat, Nitrolingual, Nitro-Dur, Nitro-Bid, and others), isosorbide dinitrate (Dilatrate-SR, Isordil, Sorbitrate), and isosorbide mononitrate (Imdur, ISMO, Monoket). Nitrates are also found in some recreational drugs such as amyl nitrate or nitrite ("poppers"). Taking Viagra with a nitrate medicine can cause a serious decrease in blood pressure, leading to fainting, stroke, or heart attack. During sexual activity, if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be having a serious side effect of Viagra. Do not take Viagra more than once a day. Allow 24 hours to pass between doses. Contact your doctor or seek emergency medical attention if your erection is painful or lasts longer than 4 hours. A prolonged erection (priapism) can damage the penis. Viagra can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking Viagra, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoke or are over 50 years old. It is not clear whether Viagra is the actual cause of vision loss. Stop using Viagra and get emergency medical help if you have sudden vision loss. Do not take Viagra if you are also using a nitrate drug for chest pain or heart problems. This includes nitroglycerin (Nitrostat, Nitrolingual, Nitro-Dur, Nitro-Bid, and others), isosorbide dinitrate (Dilatrate-SR, Isordil, Sorbitrate), and isosorbide mononitrate (Imdur, ISMO, Monoket). Nitrates are also found in some recreational drugs such as amyl nitrate or nitrite ("poppers"). Taking Viagra with a nitrate medicine can cause a serious decrease in blood pressure, leading to fainting, stroke, or heart attack. Before taking Viagra, tell your doctor if you are allergic to any drugs, or if you have: a recent history (in the past 6 months) of a heart attack, stroke, or heart rhythm disorder; a blood cell disorder such as sickle cell anemia, multiple myeloma, or leukemia; if you have been told you should not have sexual intercourse for health reasons. If you have any of these conditions, you may need a dose adjustment or special tests to safely take Viagra. Viagra can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking Viagra, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoke or are over 50 years old. It is not clear whether Viagra is the actual cause of vision loss. Stop using Viagra and get emergency medical help if you have sudden vision loss. FDA pregnancy category B: This medication is not expected to be harmful to an unborn baby. Do not use Viagra without telling your doctor if you are pregnant or plan to become pregnant during treatment. It is not known if Viagra passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby. How should I take Viagra? Take Viagra exactly as it was prescribed for you. Do not take it in larger doses or for longer than recommended by your doctor. Follow the directions on your prescription label. Revatio is usually taken three times each day, about 4 to 6 hours apart. Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. You may take it up to 4 hours before sexual activity. Do not take Viagra more than once per day. Viagra can help you have an erection when sexual stimulation occurs. An erection will not occur just by taking a pill. Follow your doctor's instructions. During sexual activity, if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be having a serious side effect of Viagra. Store this medication at room temperature away from moisture and heat. What happens if I miss a dose? Viagra is used as needed, so you are not likely to be on a dosing schedule. If you miss a dose of Revatio, take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose. What happens if I overdose? Seek emergency medical attention if you think you have used too much of this medicine. Overdose symptoms may include chest pain, nausea, irregular heartbeat, and feeling light-headed or fainting. What should I avoid while taking Viagra? Avoid drinking alcohol, which can increase some of the side effects of Viagra. Avoid using other medicines to treat impotence, such as alprostadil (Caverject, Muse, Edex) or yohimbine (Yocon, Yodoxin, others), without first talking to your doctor. Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. During sexual activity, if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be having a serious side effect of Viagra. ringing in your ears, or sudden hearing loss; chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling; swelling in your hands, ankles, or feet; feeling light-headed, fainting; or penis erection that is painful or lasts 4 hours or longer. warmth or redness in your face, neck, or chest; back pain. This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. What other drugs will affect Viagra? Do not take Viagra if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin (Nitrostat, Nitrolingual, Nitro-Dur, Nitro-Bid, Minitran, Deponit, Transderm-Nitro), isosorbide dinitrate (Dilatrate-SR, Isordil, Sorbitrate), and isosorbide mononitrate (Imdur, ISMO, Monoket), or recreational drugs such as amyl nitrate or nitrite ("poppers"). Before taking Viagra, tell your doctor about all other medications you use for erectile dysfunction, or if you are using any of the following medications: cimetidine (Tagamet, Tagamet HB); an antibiotic such as erythromycin (E-Mycin, Eryc, Ery-Tab) or clarithromycin (Biaxin); doxazosin (Cardura), prazosin (Minipress), Terazosin (Hytrin); HIV medicines such as amprenavir (Agenerase), tipranavir (Aptivus), darunavir (Prezista), efavirenz (Sustiva), nevirapine (Viramune), indinavir (Crixivan), saquinavir (Invirase, Fortovase), lopinavir/ritonavir (Kaletra), fosamprenavir (Lexiva), ritonavir (Norvir), atazanavir (Reyataz), or nelfinavir (Viracept); carbamazepine (Tegretol), phenobarbital (Luminal), or phenytoin (Dilantin); or rifampin (Rifadin, Rimactane) or rifabutin (Mycobutin). This list is not complete and there may be other drugs that can interact with Viagra. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Where can I get more information? Your pharmacist can provide more information about Viagra. What does my medication look like? Sildenafil is available with a prescription under the brand names Viagra and Revatio. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you. Revatio 20 mg - white, film-coated round tablets Viagra 25 mg - blue, film-coated tablets with a rounded-diamond shape Viagra 50 mg - blue, film-coated tablets with a rounded-diamond shape Viagra 100 mg - blue, film-coated tablets with a rounded-diamond shape Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed. Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist..
An oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cgmp)-specific phosphodiesterase type 5 (pde5). sildenafil citrate is designated chemically as 1 - [[3 - (6,7 - dihydro - 1 - methyl - 7 - oxo - 3 - propyl - 1h - pyrazolo[4,3 - d]pyrimidin - 5 - yl) - 4 - ethoxyphenyl]sulfonyl] - 4 - methylpiperazine citrate and has the following structural formula: sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/ml in water and a molecular weight of 666.7. viagra (sildenafil citrate) is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. in addition to the active ingredient, sildenafil citrate, each tablet contains the following inactive ingredients: microcrystalline cellulose, anhydrous dibasic calcium phosphate, croscarmellose sodium, magnesium stearate, hypromellose, titanium dioxide, lactose, triacetin, and fd & c blue #2 aluminum lake. the physiologic mechanism of erection of the penis involves release of nitric oxide (no) in the corpus cavernosum during sexual stimulation. no then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cgmp), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. sildenafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide (no) by inhibiting phosphodiesterase type 5 (pde5), which is responsible for degradation of cgmp in the corpus cavernosum. when sexual stimulation causes local release of no, inhibition of pde5 by sildenafil causes increased levels of cgmp in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. sildenafil at recommended doses has no effect in the absence of sexual stimulation. studies in vitro have shown that sildenafil is selective for pde5. its effect is more potent on pde5 than on other known phosphodiesterases (10-fold for pde6, >80-fold for pde1, >700-fold for pde2, pde3, pde4, pde7, pde8, pde9, pde10, and pde11). the approximately 4,000-fold selectivity for pde5 versus pde3 is important because pde3 is involved in control of cardiac contractility. sildenafil is only about 10-fold as potent for pde5 compared to pde6, an enzyme found in the retina which is involved in the phototransduction pathway of the retina. this lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels (see ). in addition to human corpus cavernosum smooth muscle, pde5 is also found in lower concentrations in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle. the inhibition of pde5 in these tissues by sildenafil may be the basis for the enhanced platelet antiaggregatory activity of nitric oxide observed in vitro, an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo. viagra is rapidly absorbed after oral administration, with absolute bioavailability of about 40%. its pharmacokinetics are dose-proportional over the recommended dose range. it is eliminated predominantly by hepatic metabolism (mainly cytochrome p450 3a4) and is converted to an active metabolite with properties similar to the parent, sildenafil. the concomitant use of potent cytochrome p450 3a4 inhibitors (e.g., erythromycin, ketoconazole, itraconazole) as well as the nonspecific cyp inhibitor, cimetidine, is associated with increased plasma levels of sildenafil (see ). both sildenafil and the metabolite have terminal half lives of about 4 hours. in healthy male volunteers. viagra is rapidly absorbed. maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. when viagra is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in t of 29%. the mean steady state volume of distribution (vss) for sildenafil is 105 l, indicating distribution into the tissues. sildenafil and its major circulating n-desmethyl metabolite are both approximately 96% bound to plasma proteins. protein binding is independent of total drug concentrations. based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0.001% of the administered dose may appear in the semen of patients. sildenafil is cleared predominantly by the cyp3a4 (major route) and cyp2c9 (minor route) hepatic microsomal isoenzymes. the major circulating metabolite results from n-desmethylation of sildenafil, and is itself further metabolized. this metabolite has a pde selectivity profile similar to sildenafil and an in vitro potency for pde5 approximately 50% of the parent drug. plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil, so that the metabolite accounts for about 20% of sildenafil's pharmacologic effects. after either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach. healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, with free plasma concentrations approximately 40% greater than those seen in healthy younger volunteers (18–45 years). in volunteers with mild (clcr=50–80 ml/min) and moderate (clcr=30–49 ml/min) renal impairment, the pharmacokinetics of a single oral dose of viagra (50 mg) were not altered. in volunteers with severe (clcr=<30 ml/min) renal impairment, sildenafil clearance was reduced, resulting in approximately doubling of auc and c compared to age-matched volunteers with no renal impairment. in volunteers with hepatic cirrhosis (child-pugh a and b), sildenafil clearance was reduced, resulting in increases in auc (84%) and c (47%) compared to age-matched volunteers with no hepatic impairment. therefore, age >65, hepatic impairment and severe renal impairment are associated with increased plasma levels of sildenafil. a starting oral dose of 25 mg should be considered in those patients (see ). in eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction, sexual stimulation resulted in improved erections, as assessed by an objective measurement of hardness and duration of erections (rigiscan ), after viagra administration compared with placebo. most studies assessed the efficacy of viagra approximately 60 minutes post dose. the erectile response, as assessed by rigiscan , generally increased with increasing sildenafil dose and plasma concentration. the time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours. single oral doses of sildenafil (100 mg) administered to healthy volunteers produced decreases in supine blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8.4/5.5 mmhg). the decrease in blood pressure was most notable approximately 1–2 hours after dosing, and was not different than placebo at 8 hours. similar effects on blood pressure were noted with 25 mg, 50 mg and 100 mg of viagra, therefore the effects are not related to dose or plasma levels within this dosage range. larger effects were recorded among patients receiving concomitant nitrates (see ). systolic blood pressure, healthy volunteers. single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ecgs of normal male volunteers. studies have produced relevant data on the effects of viagra on cardiac output. in one small, open-label, uncontrolled, pilot study, eight patients with stable ischemic heart disease underwent swan-ganz catheterization. a total dose of 40 mg sildenafil was administered by four intravenous infusions. the results from this pilot study are shown in table 1; the mean resting systolic and diastolic blood pressures decreased by 7% and 10% compared to baseline in these patients. mean resting values for right atrial pressure, pulmonary artery pressure, pulmonary artery occluded pressure and cardiac output decreased by 28%, 28%, 20% and 7% respectively. even though this total dosage produced plasma sildenafil concentrations which were approximately 2 to 5 times higher than the mean maximum plasma concentrations following a single oral dose of 100 mg in healthy male volunteers, the hemodynamic response to exercise was preserved in these patients. in a double-blind study, 144 patients with erectile dysfunction and chronic stable angina limited by exercise, not receiving chronic oral nitrates, were randomized to a single dose of placebo or viagra 100 mg 1 hour prior to exercise testing. the primary endpoint was time to limiting angina in the evaluable cohort. the mean times (adjusted for baseline) to onset of limiting angina were 423.6 and 403.7 seconds for sildenafil (n=70) and placebo, respectively. these results demonstrated that the effect of viagra on the primary endpoint was statistically non-inferior to placebo. at single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination (blue/green) was detected using the farnsworth-munsell 100-hue test, with peak effects near the time of peak plasma levels. this finding is consistent with the inhibition of pde6, which is involved in phototransduction in the retina. an evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of viagra on visual acuity, intraocular pressure, or pupillometry. in clinical studies, viagra was assessed for its effect on the ability of men with erectile dysfunction (ed) to engage in sexual activity and in many cases specifically on the ability to achieve and maintain an erection sufficient for satisfactory sexual activity. viagra was evaluated primarily at doses of 25 mg, 50 mg and 100 mg in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in duration, using a variety of study designs (fixed dose, titration, parallel, crossover). viagra was administered to more than 3,000 patients aged 19 to 87 years, with ed of various etiologies (organic, psychogenic, mixed) with a mean duration of 5 years. viagra demonstrated statistically significant improvement compared to placebo in all 21 studies. the studies that established benefit demonstrated improvements in success rates for sexual intercourse compared with placebo. the effectiveness of viagra was evaluated in most studies using several assessment instruments. the primary measure in the principal studies was a sexual function questionnaire (the international index of erectile function - iief) administered during a 4-week treatment-free run-in period, at baseline, at follow-up visits, and at the end of double-blind, placebo-controlled, at-home treatment. two of the questions from the iief served as primary study endpoints; categorical responses were elicited to questions about (1) the ability to achieve erections sufficient for sexual intercourse and (2) the maintenance of erections after penetration. the patient addressed both questions at the final visit for the last 4 weeks of the study. the possible categorical responses to these questions were (0) no attempted intercourse, (1) never or almost never, (2) a few times, (3) sometimes, (4) most times, and (5) almost always or always. also collected as part of the iief was information about other aspects of sexual function, including information on erectile function, orgasm, desire, satisfaction with intercourse, and overall sexual satisfaction. sexual function data were also recorded by patients in a daily diary. in addition, patients were asked a global efficacy question and an optional partner questionnaire was administered. the effect on one of the major end points, maintenance of erections after penetration, is shown in figure 3, for the pooled results of 5 fixed-dose, dose-response studies of greater than one month duration, showing response according to baseline function. results with all doses have been pooled, but scores showed greater improvement at the 50 and 100 mg doses than at 25 mg. the pattern of responses was similar for the other principal question, the ability to achieve an erection sufficient for intercourse. the titration studies, in which most patients received 100 mg, showed similar results. figure 3 shows that regardless of the baseline levels of function, subsequent function in patients treated with viagra was better than that seen in patients treated with placebo. at the same time, on-treatment function was better in treated patients who were less impaired at baseline. figure 3. effect of viagra and placebo on maintenance of erection by baseline score. the frequency of patients reporting improvement of erections in response to a global question in four of the randomized, double-blind, parallel, placebo-controlled fixed dose studies (1797 patients) of 12 to 24 weeks duration is shown in figure 4. these patients had erectile dysfunction at baseline that was characterized by median categorical scores of 2 (a few times) on principal iief questions. erectile dysfunction was attributed to organic (58%; generally not characterized, but including diabetes and excluding spinal cord injury), psychogenic (17%), or mixed (24%) etiologies. sixty-three percent, 74%, and 82% of the patients on 25 mg, 50 mg and 100 mg of viagra, respectively, reported an improvement in their erections, compared to 24% on placebo. in the titration studies (n=644) (with most patients eventually receiving 100 mg), results were similar. figure 4. percentage of patients reporting an improvement in erections. the patients in studies had varying degrees of ed. one-third to one-half of the subjects in these studies reported successful intercourse at least once during a 4-week, treatment-free run-in period. in many of the studies, of both fixed dose and titration designs, daily diaries were kept by patients. in these studies, involving about 1600 patients, analyses of patient diaries showed no effect of viagra on rates of attempted intercourse (about 2 per week), but there was clear treatment-related improvement in sexual function: per patient weekly success rates averaged 1.3 on 50–100 mg of viagra vs 0.4 on placebo; similarly, group mean success rates (total successes divided by total attempts) were about 66% on viagra vs about 20% on placebo. during 3 to 6 months of double-blind treatment or longer-term (1 year), open-label studies, few patients withdrew from active treatment for any reason, including lack of effectiveness. at the end of the long-term study, 88% of patients reported that viagra improved their erections. men with untreated ed had relatively low baseline scores for all aspects of sexual function measured (again using a 5-point scale) in the iief. viagra improved these aspects of sexual function: frequency, firmness and maintenance of erections; frequency of orgasm; frequency and level of desire; frequency, satisfaction and enjoyment of intercourse; and overall relationship satisfaction. one randomized, double-blind, flexible-dose, placebo-controlled study included only patients with erectile dysfunction attributed to complications of diabetes mellitus (n=268). as in the other titration studies, patients were started on 50 mg and allowed to adjust the dose up to 100 mg or down to 25 mg of viagra; all patients, however, were receiving 50 mg or 100 mg at the end of the study. there were highly statistically significant improvements on the two principal iief questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) on viagra compared to placebo. on a global improvement question, 57% of viagra patients reported improved erections versus 10% on placebo. diary data indicated that on viagra, 48% of intercourse attempts were successful versus 12% on placebo. one randomized, double-blind, placebo-controlled, crossover, flexible-dose (up to 100 mg) study of patients with erectile dysfunction resulting from spinal cord injury (n=178) was conducted. the changes from baseline in scoring on the two end point questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) were highly statistically significantly in favor of viagra. on a global improvement question, 83% of patients reported improved erections on viagra versus 12% on placebo. diary data indicated that on viagra, 59% of attempts at sexual intercourse were successful compared to 13% on placebo. across all trials, viagra improved the erections of 43% of radical prostatectomy patients compared to 15% on placebo. subgroup analyses of responses to a global improvement question in patients with psychogenic etiology in two fixed-dose studies (total n=179) and two titration studies (total n=149) showed 84% of viagra patients reported improvement in erections compared with 26% of placebo. the changes from baseline in scoring on the two end point questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) were highly statistically significantly in favor of viagra. diary data in two of the studies (n=178) showed rates of successful intercourse per attempt of 70% for viagra and 29% for placebo. a review of population subgroups demonstrated efficacy regardless of baseline severity, etiology, race and age. viagra was effective in a broad range of ed patients, including those with a history of coronary artery disease, hypertension, other cardiac disease, peripheral vascular disease, diabetes mellitus, depression, coronary artery bypass graft (cabg), radical prostatectomy, transurethral resection of the prostate (turp) and spinal cord injury, and in patients taking antidepressants/antipsychotics and antihypertensives/diuretics. analysis of the safety database showed no apparent difference in the side effect profile in patients taking viagra with and without antihypertensive medication. this analysis was performed retrospectively, and was not powered to detect any pre-specified difference in adverse reactions. viagra is indicated for the treatment of erectile dysfunction. ), viagra was shown to potentiate the hypotensive effects of nitrates, and its administration to patients who are using organic nitrates, either regularly and/or intermittently, in any form is therefore contraindicated. after patients have taken viagra, it is unknown when nitrates, if necessary, can be safely administered. based on the pharmacokinetic profile of a single 100 mg oral dose given to healthy normal volunteers, the plasma levels of sildenafil at 24 hours post dose are approximately 2 ng/ml (compared to peak plasma levels of approximately 440 ng/ml) (see ). in the following patients: age >65, hepatic impairment (e.g., cirrhosis), severe renal impairment (e.g., creatinine clearance <30 ml/min), and concomitant use of potent cytochrome p450 3a4 inhibitors (erythromycin), plasma levels of sildenafil at 24 hours post dose have been found to be 3 to 8 times higher than those seen in healthy volunteers. although plasma levels of sildenafil at 24 hours post dose are much lower than at peak concentration, it is unknown whether nitrates can be safely coadministered at this time point. viagra is contraindicated in patients with a known hypersensitivity to any component of the tablet. there is a potential for cardiac risk of sexual activity in patients with preexisting cardiovascular disease. therefore, treatments for erectile dysfunction, including viagra, should not be generally used in men for whom sexual activity is inadvisable because of their underlying cardiovascular status. viagra has systemic vasodilatory properties that resulted in transient decreases in supine blood pressure in healthy volunteers (mean maximum decrease of 8.4/5.5 mmhg), (see ). while this normally would be expected to be of little consequence in most patients, prior to prescribing viagra, physicians should carefully consider whether their patients with underlying cardiovascular disease could be affected adversely by such vasodilatory effects, especially in combination with sexual activity. patients with the following underlying conditions can be particularly sensitive to the actions of vasodilators including viagra – those with left ventricular outflow obstruction (e.g. aortic stenosis, idiopathic hypertrophic subaortic stenosis) and those with severely impaired autonomic control of blood pressure. there is no controlled clinical data on the safety or efficacy of viagra in the following groups; if prescribed, this should be done with caution. patients who have suffered a myocardial infarction, stroke, or life-threatening arrhythmia within the last 6 months; patients with retinitis pigmentosa (a minority of these patients have genetic disorders of retinal phosphodiesterases). prolonged erection greater than 4 hours and priapism (painful erections greater than 6 hours in duration) have been reported infrequently since market approval of viagra. in the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance. if priapism is not treated immediately, penile tissue damage and permanent loss of potency could result. the concomitant administration of the protease inhibitor ritonavir substantially increases serum concentrations of sildenafil (11-fold increase in auc). if viagra is prescribed to patients taking ritonavir, caution should be used. data from subjects exposed to high systemic levels of sildenafil are limited. visual disturbances occurred more commonly at higher levels of sildenafil exposure. decreased blood pressure, syncope, and prolonged erection were reported in some healthy volunteers exposed to high doses of sildenafil (200–800 mg). to decrease the chance of adverse events in patients taking ritonavir, a decrease in sildenafil dosage is recommended (see , ). the evaluation of erectile dysfunction should include a determination of potential underlying causes and the identification of appropriate treatment following a complete medical assessment. before prescribing viagra, it is important to note the following: caution is advised when phosphodiesterase type 5 (pde5) inhibitors are co-administered with alpha-blockers. pde5 inhibitors, including viagra, and alpha-adrenergic blocking agents are both vasodilators with blood pressure lowering effects. when vasodilators are used in combination, an additive effect on blood pressure may be anticipated. in some patients, concomitant use of these two drug classes can lower blood pressure significantly (see ) leading to symptomatic hypotension (e.g. dizziness, lightheadedness, fainting). patients should be stable on alpha-blocker therapy prior to initiating a pde5 inhibitor. patients who demonstrate hemodynamic instability on alpha-blocker therapy alone are at increased risk of symptomatic hypotension with concomitant use of pde5 inhibitors. in those patients who are stable on alpha-blocker therapy, pde5 inhibitors should be initiated at the lowest dose. in those patients already taking an optimized dose of a pde5 inhibitor, alpha-blocker therapy should be initiated at the lowest dose. stepwise increase in alpha-blocker dose may be associated with further lowering of blood pressure when taking a pde5 inhibitor. safety of combined use of pde5 inhibitors and alpha-blockers may be affected by other variables, including intravascular volume depletion and other anti-hypertensive drugs. viagra has systemic vasodilatory properties and may augment the blood pressure lowering effect of other anti-hypertensive medications. patients on multiple antihypertensive medications were included in the pivotal clinical trials for viagra. in a separate drug interaction study, when amlodipine, 5 mg or 10 mg, and viagra, 100 mg were orally administered concomitantly to hypertensive patients mean additional blood pressure reduction of 8 mmhg systolic and 7 mmhg diastolic were noted (see ). the safety of viagra is unknown in patients with bleeding disorders and patients with active peptic ulceration. viagra should be used with caution in patients with anatomical deformation of the penis (such as angulation, cavernosal fibrosis or peyronie's disease), or in patients who have conditions which may predispose them to priapism (such as sickle cell anemia, multiple myeloma, or leukemia). the safety and efficacy of combinations of viagra with other treatments for erectile dysfunction have not been studied. therefore, the use of such combinations is not recommended. in humans, viagra has no effect on bleeding time when taken alone or with aspirin. in vitro studies with human platelets indicate that sildenafil potentiates the antiaggregatory effect of sodium nitroprusside (a nitric oxide donor). the combination of heparin and viagra had an additive effect on bleeding time in the anesthetized rabbit, but this interaction has not been studied in humans. physicians should discuss with patients the contraindication of viagra with regular and/or intermittent use of organic nitrates. physicians should advise patients of the potential for viagra to augment the blood pressure lowering effect of alpha-blockers and anti-hypertensive medications. concomitant administration of viagra and an alpha-blocker may lead to symptomatic hypotension in some patients. therefore, when viagra is co-administered with alpha-blockers, patients should be stable on alpha-blocker therapy prior to initiating viagra treatment and viagra should be initiated at the lowest dose. physicians should discuss with patients the potential cardiac risk of sexual activity in patients with preexisting cardiovascular risk factors. patients who experience symptoms (e.g., angina pectoris, dizziness, nausea) upon initiation of sexual activity should be advised to refrain from further activity and should discuss the episode with their physician. physicians should advise patients to stop use of all pde5 inhibitors, including viagra, and seek medical attention in the event of a sudden loss of vision in one or both eyes. such an event may be a sign of non-arteritic anterior ischemic optic neuropathy (naion), a cause of decreased vision including permanent loss of vision, that has been reported rarely post-marketing in temporal association with the use of all pde5 inhibitors. it is not possible to determine whether these events are related directly to the use of pde5 inhibitors or to other factors. physicians should also discuss with patients the increased risk of naion in individuals who have already experienced naion in one eye, including whether such individuals could be adversely affected by use of vasodilators, such as pde5 inhibitors (see ). physicians should advise patients to stop taking pde5 inhibitors, including viagra, and seek prompt medical attention in the event of sudden decrease or loss of hearing. these events, which may be accompanied by tinnitus and dizziness, have been reported in temporal association to the intake of pde5 inhibitors, including viagra. it is not possible to determine whether these events are related directly to the use of pde5 inhibitors or to other factors (see , ). physicians should warn patients that prolonged erections greater than 4 hours and priapism (painful erections greater than 6 hours in duration) have been reported infrequently since market approval of viagra. in the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance. if priapism is not treated immediately, penile tissue damage and permanent loss of potency may result. the use of viagra offers no protection against sexually transmitted diseases. counseling of patients about the protective measures necessary to guard against sexually transmitted diseases, including the human immunodeficiency virus (hiv), may be considered. sildenafil metabolism is principally mediated by the cytochrome p450 (cyp) isoforms 3a4 (major route) and 2c9 (minor route). therefore, inhibitors of these isoenzymes may reduce sildenafil clearance. cimetidine (800 mg), a nonspecific cyp inhibitor, caused a 56% increase in plasma sildenafil concentrations when coadministered with viagra (50 mg) to healthy volunteers. when a single 100 mg dose of viagra was administered with erythromycin, a specific cyp3a4 inhibitor, at steady state (500 mg bid for 5 days), there was a 182% increase in sildenafil systemic exposure (auc). in addition, in a study performed in healthy male volunteers, coadministration of the hiv protease inhibitor saquinavir, also a cyp3a4 inhibitor, at steady state (1200 mg tid) with viagra (100 mg single dose) resulted in a 140% increase in sildenafil c and a 210% increase in sildenafil auc. viagra had no effect on saquinavir pharmacokinetics. stronger cyp3a4 inhibitors such as ketoconazole or itraconazole would be expected to have still greater effects, and population data from patients in clinical trials did indicate a reduction in sildenafil clearance when it was coadministered with cyp3a4 inhibitors (such as ketoconazole, erythromycin, or cimetidine) (see ). in another study in healthy male volunteers, coadministration with the hiv protease inhibitor ritonavir, which is a highly potent p450 inhibitor, at steady state (500 mg bid) with viagra (100 mg single dose) resulted in a 300% (4-fold) increase in sildenafil c and a 1000% (11-fold) increase in sildenafil plasma auc. at 24 hours the plasma levels of sildenafil were still approximately 200 ng/ml, compared to approximately 5 ng/ml when sildenafil was dosed alone. this is consistent with ritonavir's marked effects on a broad range of p450 substrates. viagra had no effect on ritonavir pharmacokinetics (see ). although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels. in a study of healthy male volunteers, co-administration of sildenafil at steady state (80 mg t.i.d.) with endothelin receptor antagonist bosentan (a moderate inducer of cyp3a4, cyp2c9 and possibly of cytochrome p450 2c19) at steady state (125 mg b.i.d.) resulted in a 63% decrease of sildenafil auc and a 55% decrease in sildenafil c . concomitant administration of strong cyp3a4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil. single doses of antacid (magnesium hydroxide/aluminum hydroxide) did not affect the bioavailability of viagra. pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of cyp2c9 inhibitors (such as tolbutamide, warfarin), cyp2d6 inhibitors (such as selective serotonin reuptake inhibitors, tricyclic antidepressants), thiazide and related diuretics, ace inhibitors, and calcium channel blockers. the auc of the active metabolite, n-desmethyl sildenafil, was increased 62% by loop and potassium-sparing diuretics and 102% by nonspecific beta-blockers. these effects on the metabolite are not expected to be of clinical consequence. sildenafil is a weak inhibitor of the cytochrome p450 isoforms 1a2, 2c9, 2c19, 2d6, 2e1 and 3a4 (ic50 >150 µm). given sildenafil peak plasma concentrations of approximately 1 µm after recommended doses, it is unlikely that viagra will alter the clearance of substrates of these isoenzymes. three double-blind, placebo-controlled, randomized, two-way crossover studies were conducted to assess the interaction of viagra with doxazosin, an alpha-adrenergic blocking agent. in the first study, a single oral dose of viagra 100 mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia (bph). following at least 14 consecutive daily doses of doxazosin, viagra 100 mg or matching placebo was administered simultaneously with doxazosin. following a review of the data from these first 4 subjects (details provided below), the viagra dose was reduced to 25 mg. thereafter, 17 subjects were treated with viagra 25 mg or matching placebo in combination with doxazosin 4 mg (15 subjects) or doxazosin 8mg (2 subjects). the mean subject age was 66.5 years. for the 17 subjects who received viagra 25 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% ci) in systolic blood pressure were as follows: blood pressure was measured immediately pre-dose and at 15, 30, 45 minutes, and 1, 1.5, 2, 2.5, 3, 4, 6 and 8 hours after viagra or matching placebo. outliers were defined as subjects with a standing systolic blood pressure of <85 mmhg or a decrease from baseline in standing systolic blood pressure of >30 mmhg at one or more timepoints. there were no subjects treated with viagra 25 mg who had a standing sbp < 85mmhg. there were three subjects with a decrease from baseline in standing systolic bp >30mmhg following viagra 25 mg, one subject with a decrease from baseline in standing systolic bp > 30 mmhg following placebo and two subjects with a decrease from baseline in standing systolic bp > 30 mmhg following both viagra and placebo. no severe adverse events potentially related to blood pressure effects were reported in this group. of the four subjects who received viagra 100 mg in the first part of this study, a severe adverse event related to blood pressure effect was reported in one patient (postural hypotension that began 35 minutes after dosing with viagra with symptoms lasting for 8 hours), and mild adverse events potentially related to blood pressure effects were reported in two others (dizziness, headache and fatigue at 1 hour after dosing; and dizziness, lightheadedness and nausea at 4 hours after dosing). there were no reports of syncope among these patients. for these four subjects, the placebo-subtracted mean maximum decreases from baseline in supine and standing systolic blood pressures were 14.8 mmhg and 21.5 mmhg, respectively. two of these subjects had a standing sbp < 85mmhg. both of these subjects were protocol violators, one due to a low baseline standing sbp, and the other due to baseline orthostatic hypotension. in the second study, a single oral dose of viagra 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with bph. following at least 14 consecutive days of doxazosin, viagra 50mg or matching placebo was administered simultaneously with doxazosin 4 mg (17 subjects) or with doxazosin 8 mg (3 subjects). the mean subject age in this study was 63.9 years. twenty subjects received viagra 50 mg, but only 19 subjects received matching placebo. one patient discontinued the study prematurely due to an adverse event of hypotension following dosing with viagra 50 mg. this patient had been taking minoxidil, a potent vasodilator, during the study. for the 19 subjects who received both viagra and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% ci) in systolic blood pressure were as follows: blood pressure was measured after administration of viagra at the same times as those specified for the first doxazosin study. there were two subjects who had a standing sbp of < 85 mmhg. in these two subjects, hypotension was reported as a moderately severe adverse event, beginning at approximately 1 hour after administration of viagra 50 mg and resolving after approximately 7.5 hours. there was one subject with a decrease from baseline in standing systolic bp >30mmhg following viagra 50 mg and one subject with a decrease from baseline in standing systolic bp > 30 mmhg following both viagra 50 mg and placebo. there were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study. in the third study, a single oral dose of viagra 100 mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with bph. in dose period 1, subjects were administered open-label doxazosin and a single dose of viagra 50 mg simultaneously, after at least 14 consecutive days of doxazosin. if a subject did not successfully complete this first dosing period, he was discontinued from the study. subjects who had successfully completed the previous doxazosin interaction study (using viagra 50 mg), including no significant hemodynamic adverse events, were allowed to skip dose period 1. treatment with doxazosin continued for at least 7 days after dose period 1. thereafter, viagra 100mg or matching placebo was administered simultaneously with doxazosin 4 mg (14 subjects) or doxazosin 8 mg (6 subjects) in standard crossover fashion. the mean subject age in this study was 66.4 years. twenty-five subjects were screened. two were discontinued after study period 1: one failed to meet pre-dose screening qualifications and the other experienced symptomatic hypotension as a moderately severe adverse event 30 minutes after dosing with open-label viagra 50 mg. of the twenty subjects who were ultimately assigned to treatment, a total of 13 subjects successfully completed dose period 1, and seven had successfully completed the previous doxazosin study (using viagra 50 mg). for the 20 subjects who received viagra 100 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% ci) in systolic blood pressure were as follows: blood pressure was measured after administration of viagra at the same times as those specified for the previous doxazosin studies. there were three subjects who had a standing sbp of < 85 mmhg. all three were taking viagra 100 mg, and all three reported mild adverse events at the time of reductions in standing sbp, including vasodilation and lightheadedness. there were four subjects with a decrease from baseline in standing systolic bp >30mmhg following viagra 100 mg, one subject with a decrease from baseline in standing systolic bp > 30 mmhg following placebo and one subject with a decrease from baseline in standing systolic bp > 30 mmhg following both viagra and placebo. while there were no severe adverse events potentially related to blood pressure reported in this study, one subject reported moderate vasodilatation after both viagra 50 mg and 100 mg. there were no episodes of syncope reported in this study. when viagra 100 mg oral was coadministered with amlodipine, 5 mg or 10 mg oral, to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmhg systolic and 7 mmhg diastolic. no significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by cyp2c9. viagra (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg). viagra (50 mg) did not potentiate the hypotensive effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 0.08%. in a study of healthy male volunteers, sildenafil (100 mg) did not affect the steady state pharmacokinetics of the hiv protease inhibitors, saquinavir and ritonavir, both of which are cyp3a4 substrates. sildenafil at steady state (80 mg t.i.d.) resulted in a 50% increase in auc and a 42% increase in c of bosentan (125 mg b.i.d.). carcinogenesis, mutagenesis, impairment of fertility sildenafil was not carcinogenic when administered to rats for 24 months at a dose resulting in total systemic drug exposure (aucs) for unbound sildenafil and its major metabolite of 29- and 42-times, for male and female rats, respectively, the exposures observed in human males given the maximum recommended human dose (mrhd) of 100 mg. sildenafil was not carcinogenic when administered to mice for 18–21 months at dosages up to the maximum tolerated dose (mtd) of 10 mg/kg/day, approximately 0.6 times the mrhd on a mg/m basis. sildenafil was negative in in vitro bacterial and chinese hamster ovary cell assays to detect mutagenicity, and in vitro human lymphocytes and in vivo mouse micronucleus assays to detect clastogenicity. there was no impairment of fertility in rats given sildenafil up to 60 mg/kg/day for 36 days to females and 102 days to males, a dose producing an auc value of more than 25 times the human male auc. there was no effect on sperm motility or morphology after single 100 mg oral doses of viagra in healthy volunteers. pregnancy, nursing mothers and pediatric use viagra is not indicated for use in newborns, children, or women. no evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received up to 200 mg/kg/day during organogenesis. these doses represent, respectively, about 20 and 40 times the mrhd on a mg/m basis in a 50 kg subject. in the rat pre- and postnatal development study, the no observed adverse effect dose was 30 mg/kg/day given for 36 days. in the nonpregnant rat the auc at this dose was about 20 times human auc. there are no adequate and well-controlled studies of sildenafil in pregnant women. ). since higher plasma levels may increase both the efficacy and incidence of adverse events, a starting dose of 25 mg should be considered (see ). viagra was administered to over 3700 patients (aged 19–87 years) during pre-marketing clinical trials worldwide. over 550 patients were treated for longer than one year. in placebo-controlled clinical studies, the discontinuation rate due to adverse events for viagra (2.5%) was not significantly different from placebo (2.3%). the adverse events were generally transient and mild to moderate in nature. in trials of all designs, adverse events reported by patients receiving viagra were generally similar. in fixed-dose studies, the incidence of some adverse events increased with dose. the nature of the adverse events in flexible-dose studies, which more closely reflect the recommended dosage regimen, was similar to that for fixed-dose studies. when viagra was taken as recommended (on an as-needed basis) in flexible-dose, placebo-controlled clinical trials, the following adverse events were reported: other adverse reactions occurred at a rate of >2%, but equally common on placebo: respiratory tract infection, back pain, flu syndrome, and arthralgia. in fixed-dose studies, dyspepsia (17%) and abnormal vision (11%) were more common at 100 mg than at lower doses. at doses above the recommended dose range, adverse events were similar to those detailed above but generally were reported more frequently. the following events occurred in <2% of patients in controlled clinical trials; a causal relationship to viagra is uncertain. reported events include those with a plausible relation to drug use; omitted are minor events and reports too imprecise to be meaningful: body as a whole: face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injury. cardiovascular: angina pectoris, av block, migraine, syncope, tachycardia, palpitation, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathy. digestive: vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, liver function tests abnormal, rectal hemorrhage, gingivitis. hemic and lymphatic: anemia and leukopenia. metabolic and nutritional: thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremia. musculoskeletal: arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitis. nervous: ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams, reflexes decreased, hypesthesia. respiratory: asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum increased, cough increased. skin and appendages: urticaria, herpes simplex, pruritus, sweating, skin ulcer, contact dermatitis, exfoliative dermatitis. special senses: sudden decrease or loss of hearing, mydriasis, conjunctivitis, photophobia, tinnitus, eye pain, ear pain, eye hemorrhage, cataract, dry eyes. urogenital: cystitis, nocturia, urinary frequency, breast enlargement, urinary incontinence, abnormal ejaculation, genital edema and anorgasmia. serious cardiovascular, cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, subarachnoid and intracerebral hemorrhages, and pulmonary hemorrhage have been reported post-marketing in temporal association with the use of viagra. most, but not all, of these patients had preexisting cardiovascular risk factors. many of these events were reported to occur during or shortly after sexual activity, and a few were reported to occur shortly after the use of viagra without sexual activity. others were reported to have occurred hours to days after the use of viagra and sexual activity. it is not possible to determine whether these events are related directly to viagra, to sexual activity, to the patient's underlying cardiovascular disease, to a combination of these factors, or to other factors (see for further important cardiovascular information). cases of sudden decrease or loss of hearing have been reported postmarketing in temporal association with the use of pde5 inhibitors, including viagra. in some of the cases, medical conditions and other factors were reported that may have also played a role in the otologic adverse events. in many cases, medical follow-up information was limited. it is not possible to determine whether these reported events are related directly to the use of viagra, to the patient’s underlying risk factors for hearing loss, a combination of these factors, or to other factors (see ). nervous: seizure and anxiety. urogenital: prolonged erection, priapism (see ), and hematuria. special senses: diplopia, temporary vision loss/decreased vision, ocular redness or bloodshot appearance, ocular burning, ocular swelling/pressure, increased intraocular pressure, retinal vascular disease or bleeding, vitreous detachment/traction, paramacular edema and epistaxis. non-arteritic anterior ischemic optic neuropathy (naion), a cause of decreased vision including permanent loss of vision, has been reported rarely post-marketing in temporal association with the use of phosphodiesterase type 5 (pde5) inhibitors, including viagra. most, but not all, of these patients had underlying anatomic or vascular risk factors for developing naion, including but not necessarily limited to: low cup to disc ratio ("crowded disc"), age over 50, diabetes, hypertension, coronary artery disease, hyperlipidemia and smoking. it is not possible to determine whether these events are related directly to the use of pde5 inhibitors, to the patient's underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors (see ). in studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those seen at lower doses but incidence rates were increased. in cases of overdose, standard supportive measures should be adopted as required. renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and it is not eliminated in the urine. for most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. however, viagra may be taken anywhere from 4 hours to 0.5 hour before sexual activity. based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. the maximum recommended dosing frequency is once per day. the following factors are associated with increased plasma levels of sildenafil: age >65 (40% increase in auc), hepatic impairment (e.g., cirrhosis, 80%), severe renal impairment (creatinine clearance <30 ml/min, 100%), and concomitant use of potent cytochrome p450 3a4 inhibitors [ketoconazole, itraconazole, erythromycin (182%), saquinavir (210%)]. since higher plasma levels may increase both the efficacy and incidence of adverse events, a starting dose of 25 mg should be considered in these patients. ritonavir greatly increased the systemic level of sildenafil in a study of healthy, non-hiv infected volunteers (11-fold increase in auc, see .) based on these pharmacokinetic data, it is recommended not to exceed a maximum single dose of 25 mg of viagra in a 48 hour period. viagra was shown to potentiate the hypotensive effects of nitrates and its administration in patients who use nitric oxide donors or nitrates in any form is therefore contraindicated. when viagra is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating viagra treatment and viagra should be initiated at the lowest dose (see ). viagra (sildenafil citrate) is supplied as blue, film-coated, rounded-diamond-shaped tablets containing sildenafil citrate equivalent to the nominally indicated amount of sildenafil as follows: store at 25°c (77°f); excursions permitted to 15–30°c (59–86°f) [see usp controlled room temperature]. lab-0221-8.0 ®. it is not meant to take the place of your doctor's instructions. read this information carefully before you start taking viagra. ask your doctor or pharmacist if you do not understand any of this information or if you want to know more about viagra. this medicine can help many men when it is used as prescribed by their doctors. however, viagra is not for everyone. it is intended for use only by men who have a condition called erectile dysfunction. viagra must never be used by men who are taking medicines that contain nitrates of any kind, at any time. this includes nitroglycerin. if you take viagra with any nitrate medicine your blood pressure could suddenly drop to an unsafe or life threatening level. • what is viagra? viagra is a pill used to treat erectile dysfunction (impotence) in men. it can help many men who have erectile dysfunction get and keep an erection when they become sexually excited (stimulated). you will not get an erection just by taking this medicine. viagra helps a man with erectile dysfunction get an erection only when he is sexually excited. when a man is sexually excited, the penis rapidly fills with more blood than usual. the penis then expands and hardens. this is called an erection. after the man is done having sex, this extra blood flows out of the penis back into the body. the erection goes away. if an erection lasts for a long time (more than 6 hours), it can permanently damage your penis. you should call a doctor immediately if you ever have a prolonged erection that lasts more than 4 hours. some conditions and medicines interfere with this natural erection process. the penis cannot fill with enough blood. the man cannot have an erection. this is called erectile dysfunction if it becomes a frequent problem. during sex, your heart works harder. therefore sexual activity may not be advisable for people who have heart problems. before you start any treatment for erectile dysfunction, ask your doctor if your heart is healthy enough to handle the extra strain of having sex. if you have chest pains, dizziness or nausea during sex, stop having sex and immediately tell your doctor you have had this problem. viagra enables many men with erectile dysfunction to respond to sexual stimulation. when a man is sexually excited, viagra helps the penis fill with enough blood to cause an erection. after sex is over, the erection goes away. as noted above (how sex affects the body), ask your doctor if your heart is healthy enough for sexual activity. if you take any medicines that contain nitrates – either regularly or as needed – you should never take viagra. if you take viagra with any nitrate medicine or recreational drug containing nitrates, your blood pressure could suddenly drop to an unsafe level. you could get dizzy, faint, or even have a heart attack or stroke. nitrates are found in many prescription medicines that are used to treat angina (chest pain due to heart disease) such as: nitroglycerin (sprays, ointments, skin patches or pastes, and tablets that are swallowed or dissolved in the mouth) isosorbide mononitrate and isosorbide dinitrate (tablets that are swallowed, chewed, or dissolved in the mouth) nitrates are also found in recreational drugs such as amyl nitrate or nitrite ("poppers"). if you are not sure if any of your medicines contain nitrates, or if you do not understand what nitrates are, ask your doctor or pharmacist. viagra is only for patients with erectile dysfunction. viagra is not for newborns, children, or women. do not let anyone else take your viagra. viagra must be used only under a doctor's supervision. viagra does not cure erectile dysfunction. it is a treatment for erectile dysfunction. viagra does not protect you or your partner from getting sexually transmitted diseases, including hiv—the virus that causes aids. viagra is not a hormone or an aphrodisiac. only your doctor can decide if viagra is right for you. viagra can cause mild, temporary lowering of your blood pressure. you will need to have a thorough medical exam to diagnose your erectile dysfunction and to find out if you can safely take viagra alone or with your other medicines. your doctor should determine if your heart is healthy enough to handle the extra strain of having sex. have ever had any heart problems (e.g., angina, chest pain, heart failure, irregular heart beats, heart attack or narrowing of the aortic valve) have ever had any blood problems, including sickle cell anemia or leukemia have a deformed penis, peyronie's disease, or ever had an erection that lasted more than 4 hours some medicines can change the way viagra works. tell your doctor about any medicines you are taking. do not start or stop taking any medicines before checking with your doctor or pharmacist. this includes prescription and nonprescription medicines or remedies: remember, viagra should never be used with medicines that contain nitrates (see viagra is not for everyone). if you are taking medicines called alpha-blockers for the treatment of high blood pressure or prostate problems, your blood pressure could suddenly drop. you could get dizzy or faint. if you are taking a protease inhibitor, your dose may be adjusted (please see finding the right dose for you). viagra should not be used with any other medical treatments that cause erections. these treatments include pills, medicines that are injected or inserted into the penis, implants or vacuum pumps. viagra comes in different doses (25 mg, 50 mg and 100 mg). if you do not get the results you expect, talk with your doctor. you and your doctor can determine the dose that works best for you. do not take more viagra than your doctor prescribes. if you think you need a larger dose of viagra, check with your doctor. viagra should not be taken more than once a day. your doctor may prescribe a lower dose of viagra in certain circumstances. for example: if you are older than age 65, or have serious liver or kidney problems, your doctor may start you at the lowest dose (25 mg) of viagra. if you are taking protease inhibitors, such as for the treatment of hiv, your doctor may recommend a 25 mg dose and may limit you to a maximum single dose of 25 mg of viagra in a 48 hour period. if you have prostate problems or high blood pressure for which you take medicines called alpha blockers, your doctor may start you on a lower dose of viagra. take viagra about one hour before you plan to have sex. beginning in about 30 minutes and for up to 4 hours, viagra can help you get an erection if you are sexually excited. if you take viagra after a high-fat meal (such as a cheeseburger and french fries), the medicine may take a little longer to start working. viagra can help you get an erection when you are sexually excited. you will not get an erection just by taking the pill. like all medicines, viagra can cause some side effects. these effects are usually mild to moderate and usually don't last longer than a few hours. some of these side effects are more likely to occur with higher doses. the most common side effects of viagra are headache, flushing of the face, and upset stomach. less common side effects that may occur are temporary changes in color vision (such as trouble telling the difference between blue and green objects or having a blue color tinge to them), eyes being more sensitive to light, or blurred vision. in rare instances, men taking pde5 inhibitors (oral erectile dysfunction medicines, including viagra) reported a sudden decrease or loss of vision in one or both eyes. it is not possible to determine whether these events are related directly to these medicines, to other factors such as high blood pressure or diabetes, or to a combination of these. if you experience sudden decrease or loss of vision, stop taking pde5 inhibitors, including viagra, and call a doctor right away. in rare instances, men have reported an erection that lasts many hours. you should call a doctor immediately if you ever have an erection that lasts more than 4 hours. if not treated right away, permanent damage to your penis could occur (see how sex affects the body). sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness, has been rarely reported in people taking pde5 inhibitors, including viagra. it is not possible to determine whether these events are related directly to the pde5 inhibitors, to other diseases or medications, to other factors, or to a combination of factors. if you experience these symptoms, stop taking viagra and contact a doctor right away. heart attack, stroke, irregular heart beats, and death have been reported rarely in men taking viagra. most, but not all, of these men had heart problems before taking this medicine. it is not possible to determine whether these events were directly related to viagra. viagra may cause other side effects besides those listed on this sheet. if you want more information or develop any side effects or symptoms you are concerned about, call your doctor. in case of accidental overdose, call your doctor right away. keep viagra out of the reach of children. keep viagra in its original container. store at 25°c (77°f); excursions permitted to 15–30°c (59–86°f) [see usp controlled room temperature]. viagra is a prescription medicine used to treat erectile dysfunction. only your doctor can decide if it is right for you. this sheet is only a summary. if you have any questions or want more information about viagra, talk with your doctor or pharmacist, visit www.viagra.com, or call 1-888-4viagra. lab-0220-6.0 My girlfriend and I are very sexually active. I am very healthy sexually but when we have relations two or three times in a day, I'm a better lover if I take a Viagra. Is this healthy? Every relationship is different in terms of the frequency of intimacy. Some couples have sexual relations every 10 days, and others may crave intimacy daily or even several times a day. The key here is that both individuals need to feel that their lovemaking frequency is just right. The definition of erectile dysfunction is the inability to achieve or maintain a satisfactory erection for sexual relations. While apparently that is not a problem for your first round of lovemaking, it sounds as though you are improving your performance with Viagra when you and your girlfriend enjoy subsequent intimate relations in a short time period. There is nothing wrong with this approach medically. The important point to realize is that intimacy is physical and psychological. Just be certain that while you are fine-tuning your physical sexual abilities, that you and your girlfriend continue to fine-tune the elements that contribute to your emotional and psychological intimacy. Those elements may be as simple as sharing books, discussing lifelong secrets or becoming wine enthusiasts together. herbal viagra wholesale In the U.S.— Sildenafil (sil-DEN-a-fil) belongs to a group of medicines that delay the enzymes called phosphodiesterases from working too quickly. The penis is one of the areas where these enzymes work. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). By controlling the enzyme phosphodiesterase, sildenafil helps to maintain an erection that is produced when the penis is stroked. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection. Sildenafil is also used to treat the symptoms of pulmonary arterial hypertension. This is the high blood pressure that occurs in the main artery that carries blood from the right side of the heart (the ventricle) to the lungs. When the smaller blood vessels in the lungs become more resistant to blood flow, the right ventricle must work harder to pump enough blood through the lungs. Sildenafil helps by increasing the supply of blood to the lungs and reducing the workload of the heart. This medicine is available only with your doctor's prescription, in the following dosage form(s): Tablets (U.S.) In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For sildenafil, the following should be considered: Tell your doctor if you have ever had any unusual or allergic reaction to sildenafil. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes. Sildenafil is not indicated for use in women. Sildenafil has not been studied in pregnant women. However, sildenafil has not been shown to cause birth defects or other problems in animal studies. It is not known whether sildenafil passes into breast milk. Sildenafil is not indicated for use in women for erectile dysfunction. Mothers who are taking this medicine for pulmonary arterial hypertension and who wish to breast-feed should discuss this with their doctor. Elderly people are especially sensitive to the effects of sildenafil, which may increase their chance of having side effects. Patients 65 years of age and older who are taking this medicine for erectile dysfunction are started on a low dose, 25 mg, of sildenafil. Patients who are taking this medicine for pulmonary arterial hypertension may also need to be started at a lower dose. The dose may be increased by a doctor as needed and tolerated. Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking sildenafil, it is especially important that your health care professional know if you are taking any of the following: Alpha-blockers (medicine for high blood pressure—Sildenafil when taken together with an alpha-blocker medicine may cause very low blood pressure. Sildenafil doses above 25 mg should not be taken within 4 hours of taking an alpha-blocker medicine. Bosentan (e.g., Tracleer)—May increase amounts of bosentan in the body Cimetidine (e.g., Tagamet) Erythromycin (e.g., E.E.S. or Ery-Tab) Itraconazole (e.g., Sporanox) Ketaconazole (e.g., Nizoral) Mibefradil (e.g., Posicor) Ritonavir (e.g., Norvir) Saquinavir (e.g., Fortovase or Invirase)—These medicines may increase the unwanted effects of sildenafil, unless lower starting doses of sildenafil are used Erectile dysfunction medicines—These medicines should not be used at the same time as sildenafil because the safety of using these medicines in combination has not been proven. Nitrates, such as nitroglycerin (e.g., Nitrostat or Transderm-Nitro)—Sildenafil increases the lowering of blood pressure by nitrates too much and their use together is not recommended The presence of other medical problems may affect the use of sildenafil. Make sure you tell your doctor if you have any other medical problems, especially: Smoking—These conditions may increase risk for a serious eye problem called NAION. Heart attack, history of (within the last 6 months) or Stroke, history of (within the last 6 months)—Chance of problems occurring may be increased Abnormal penis, including curved penis and birth defects of the penis—Chance of problems occurring may be increased Retinitis pigmentosa—Chance of problems occurring may be increased. It is not known if the medicine is safe for use in these patients Conditions causing thickened blood or slower blood flow, including leukemia; multiple myeloma (tumors of the bone marrow); or polycythemia, sickle cell disease, and thrombocythemia (blood problems) or Priapism (history of)—Although sildenafil does not cause priapism (erection lasting longer than 6 hours), patients with these conditions have an increased risk of priapism and it could occur while using sildenafil Heart or blood disease—Sexual activity increases the heart rate and blood flow and can increase the chance of problems occurring for some patients who use any type of medicine, including sildenafil, that increases sexual ability Liver problems (severe)—Chance of problems occurring may be increased. Lower starting doses may be used and doses increased as needed and as tolerated NAION (serious eye condition) in one or both eyes, previously—May increase your chance of getting NAION again. Special patient directions come with sildenafil. . This medicine usually begins to work within 30 minutes after taking it for erectile dysfunction. It continues to work for up to 4 hours, although its action is usually less after 2 hours. The dose of sildenafil will be different for different patients. . The following information includes only the average doses of sildenafil. If your dose is different, do not change it unless your doctor tells you to do so. Adults up to 65 years of age—50 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. If needed, your doctor may increase your daily dose to 100 mg or decrease your daily dose to 25 mg. Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. If needed, your doctor may increase your daily dose. If you are taking protease inhibitors, such as for the treatment of HIV, your doctor may recommend a 25 mg dose and may limit you to a maximum single dose of 25 mg of Viagra in a 48 hour period Adults—20 mg three times per day. Each dose should be taken about 4 to 6 hours apart and can be taken with or without food. Children—Use and dose must be determined by your doctor. Keep out of the reach of children. Store away from heat and direct light. Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down. Keep the medicine from freezing. Do not refrigerate. Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children. Sildenafil has not been studied with other medicines used for treatment of erectile dysfunction. Presently, using them together is not recommended . . If you need emergency medical care for a heart problem, it is important that your healthcare provider knows when you last took sildenafil. . Do not use more of it and do not use it more often than your doctor ordered. If too much is used, the chance of side effects is increased. If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. This condition may require prompt medical treatment to prevent tissue damage of the penis and possible permanent impotence. This medicine does not protect you against sexually transmitted diseases. Use protective measures and ask your doctor if you have any questions about this. It is important to tell your doctor about any heart problems you may have now or may have had in the past. This medicine can cause serious side effects in patients with heart problems. If you experience sudden loss of vision in one or both eyes, stop using sildenafil and contact your doctor immediately. Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome: Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor. The information contained in the Thomson Healthcare (Micromedex) products as delivered by Drugs.com is intended as an educational aid only. It is not intended as medical advice for individual conditions or treatment. It is not a substitute for a medical exam, nor does it replace the need for services provided by medical professionals. Talk to your doctor, nurse or pharmacist before taking any prescription or over the counter drugs (including any herbal medicines or supplements) or following any treatment or regimen. Only your doctor, nurse, or pharmacist can provide you with advice on what is safe and effective for you. The use of the Thomson Healthcare products is at your sole risk. These products are provided "AS IS" and "as available" for use, without warranties of any kind, either express or implied. Thomson Healthcare and Drugs.com make no representation or warranty as to the accuracy, reliability, timeliness, usefulness or completeness of any of the information contained in the products. Additionally, THOMSON HEALTHCARE MAKES NO REPRESENTATION OR WARRANTIES AS TO THE OPINIONS OR OTHER SERVICE OR DATA YOU MAY