Viagra's glory story may be tainted--the potency pill doesn't mix well with protease inhibitors or recreational drugs
Before it even was introduced on the market, Viagra had achieved the kind of fame usually reserved for Hollywood superstars. As an easily used drug that can successfully treat male impotence, Viagra became the hottest topic in the media and provided an enormous boost to the stock of its manufacturer, Pfizer Inc., as doctors wrote tens of thousands of prescriptions in its first two weeks of availability alone. But now that the little blue pill is the Titanic of medications, doctors and mental health experts are warning gay men about the drug's potential downsides.
"I have never seen in my career a greater demand for prescriptions before a drug was released," says Gary R. Cohan, a physician at Pacific Oaks' Medical Group in Los Angeles. "There's a great demand, but there are a couple of interactions gay men need to know about."
However, dangerous side effects or not, doctors believe some men may rush to the drug without fully exploring whether they need it. "I would really caution people not to see it as a panacea but as something useful after they and their doctor work out what else is going on," says Kenneth Mayer, professor of medicine and community health at Brown University.
Viagra, treats impotence by acting on an enzyme that causes erections to subside. In men with erectile dysfunction, the enzyme is stronger than GMP, the body chemical that initiates erections. Viagra keeps the enzyme from breaking down GMP, letting it produce an erection without interference. Doctors recommend that patients take Viagra a half hour to an hour before sexual activity.
Within weeks of Viagra's introduction, AIDS Treatment News and the Gay and Lesbian Medical Association both issued alerts about potentially serious interactions between Viagra and other drugs. Their concern centered on two different circumstances during which the drug may be used: in combination with protease inhibitors and in combination with poppers, a class of recreational drugs used by some men to enhance sexual feeling.
Benjamin Schatz, executive director of the medical association, says Pfizer approached his group to discuss potential problems. "It speaks well for them," Schatz says. "Imagine a pharmaceutical company approaching a gay and lesbian medical group about something not HIV-related. On that level what they did is really important and should be applauded."
In the case of protease inhibitors, the drugs work on the same enzyme as Viagra. "Viagra is metabolized by the same enzyme that metabolizes 1protease inhibitors," Mayer says. "It's not thought that Viagra itself will influence the levels of protease inhibitors in the blood, but protease inhibitors, particularly ritonavir, can raise Viagra levels." Viagra also interacts with certain antibiotics, such as erythromycin.
Mayer says the potential side effects of the interaction are still unknown, although even at high doses Viagra does not seem to cause any long-term, serious medical problems. "Whether it translates into longer-lasting erections or more headaches is not clear," he says. "In the scheme of things, a protease inhibitor study is medically necessary, particularly when you're dealing with people who are otherwise doing well." Medical experts advise men taking protease inhibitors to limit their dosage of Viagra to 25 milligrams, half the normal suggested dose.
The issue is of particular concern because impotence is a common problem among men with HIV. Often the difficulty is caused by lowered levels of testosterone in the blood. "Viagra would probably work best in people with HIV-related erectile dysfunction if they are getting testosterone," Cohan says. "You first have to get the libido back, and then Viagra helps the blood flow to happen properly. …