What is Viagra?
Viagra (sildenafil citrate) is a medication made by Pfizer Pharmaceuticals, and is the first approved non-surgical treatment for erectile dysfunction (ED) that does not have to be either injected or inserted directly into the penis to achieve and maintain an erection. It was approved by the FDA for prescription sale at the end of March, 1998.
What is the history of the development of Viagra?
Originally developed by Pfizer as a drug to help men who were suffering from chest pain, sildenafil citrate as a heart medication did not show promise and studies were stopped in 1992.
However, based on published information about some properties contained in sildenafil citrate, Pfizer researchers began to look at it as a treatment for erectile dysfunction. It was re-evaluated for its effect on the ability of men with ED to engage in sexual activity, and the ability to achieve and maintain erection sufficient for satisfactory sexual activity.
Eventually, twenty-one randomized, placebo-controlled clinical trials involving more than 3700 patients, ages 19-87 years, were held worldwide. The participants had varying degrees of impotence associated with:
The clinical trials found Viagra to be so effective, the FDA approved it only six months after submission, and without consulting an advisory committee of outside experts because there were no troubling questions and no significant side effects.
What are the general precautions for taking Viagra?
Healthcare professionals advise cautious optimism when considering using Viagra. Although data from the clinical trials are very promising, prospective patients must have realistic expectations. The drug is not an aphrodisiac, and does not change libido or desire. Viagra does not directly cause penile erection, but affects the response to sexual stimulation.
The FDA recommends that men follow these general precautions before taking Viagra:
What are the side effects of Viagra?
In the clinical trials, when Viagra was taken on an as-recommended and as-needed basis, the following adverse events were reported:
Side effects that occurred less than 2 percent included respiratory tract infection, back pain, flu syndrome, and arthralgia (joint pain).
How does Viagra work?
The erection of the penis involves release of nitric oxide (NO), a chemical that is normally released in response to sexual stimulation, in the corpus cavernosum of the penis.
Information from the FDA:
Who should NOT take Viagra
According to FDA-updated information released in December 1998, the following people should not take Viagra:
Other FDA warnings include:
Viagra was not studied in patients who have a history of the following conditions:
Because of the blood pressure lowering effect of Viagra, your doctor will evaluate your overall medical condition to determine if this, in combination with sexual activity, could adversely affect your health.
Viagra may 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.
Regarding possible contribution of Viagra to heart attacks, sudden cardiac deaths, and hypertension:
Between March and November 1998, the FDA investigated more than 200 reported cases that involved death or serious illness. Many cases were eliminated because of unverifiable information. They concentrated on 130 deaths of men who had been prescribed the drug. Of these, "two men died from homicide and drowning; three had strokes; and 77 had cardiovascular events (41 with definite or suspected myocardial infarction, 27 with cardiac arrest, 6 with cardiac symptoms, and 3 with coronary artery disease). Cause of death was unmentioned or unknown for 48 cases."
The FDA acknowledged that number of deaths is a small percentage of the 6 million prescriptions written in that time period, and that "An accumulation of adverse event reports does not necessarily indicate that the adverse event was caused by the drug; rather, the event may be due to an underlying disease or some other factor(s)."
However, the FDA felt that label or enclosure information and warnings should be stronger. In November 1998, Pfizer revised the information in consultation with the FDA. The new labeling is intended to help make sure that consumers and doctors are fully informed about the:
As with all approved medications, the FDA continues to monitor the safety of Viagra by carefully reviewing reports of death and other serious adverse events and will continue to evaluate the need for regulatory action.
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