Preventing HIV with a Pill?

Using anti-HIV medications to prevent HIV infection is not a new concept--since 1996, antiretrovirals have been administered to prevent infection inhealth-care workers exposed to HIVthrough needle sticks--but use of anti-HIV drugs prior to risky behavioris gaining attention.

The San Francisco Chronicle reported on March 28, 2006, that a combination of tenofovir (Viread) andemtricitabine (Emtriva)--the drugs paired in the popular antiretroviral Truvada--shows promise for preventing HIV infection. Six monkeys injected with tenofovir/emtricitabineremained uninfected after 14 weekly exposures to a simian-human form of HIV. In contrast, five out of six control animals became infected.

Several clinical trials, including "Project T" in San Francisco and Atlanta, are testing the safety and prophylactic efficacy of tenofovir in humans. Reportedly, some physicians are already prescribing tenofovir to high-risk patients who do not use condoms, and some individuals are purchasing the drug at clubs or other settings.In a 2005 survey of pride events, 7% of HIV negative gay men reported using anti-HIV drugs for "protection" during unsafe sex, and roughly 20% knew someone who had.

Gilead Sciences (the maker of tenofovir, emtricitabine, and Truvada) is not promoting their drugs' preventive potential. Some researchers are particularly worried that HIV negative people who become infected while taking antiretrovirals might rapidly develop resistance, thereby limiting their treatment options. Until more is known about the prophylactic efficacy and safety of tenofovir and Truvada, it is premature for HIV negative individuals to entrust their health solely to these drugs.