The FDA has approved use of the HIV drug Truvada to help people at high risk avoid infection with the AIDS virus.

Truvada is already approved as part of treatment regimens for people with HIV infection. But this is the first time the FDA has approved any drug for "pre-exposure prophylaxis" or PrEP -- that is, for protecting uninfected people against HIV.

It is not a prescription to party, says Debra Birnkrant, MD, the FDA's director of antiviral products.

"We stress that PrEP with Truvada must include safer-sex practices, counseling, and HIV testing," Birnkrant said at a news conference held to announce the decision. "Truvada should not be used alone for HIV prevention."

Two major studies suggest that PrEP with Truvada may work as hoped:

    In the iPrEx study of 2,499 HIV-negative men and transgender women who have high-risk sex with men, those who took Truvada had 42% fewer HIV infections than those who did not. There was no evidence that taking Truvada increased unsafe sex, although study participants did not know for sure whether they were getting Truvada or an inactive placebo.
    The Partners PrEP study enrolled 4,758 heterosexual couples in which one member was infected with HIV and one was not. Truvada reduced the risk of HIV infection by 75%.

In the real world, however, it is not at all clear whether people who take Truvada will also take more risks, such as having sex without condoms or having multiple sex partners.

Moreover, Truvada must be taken every day in order to help prevent HIV infection. People in clinical trials did this. But if that doesn't happen in the real world, people who get infected while taking too few doses likely will end up with drug-resistant HIV infection that they can then spread to others.

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"The FDA's move today is negligence bordering the equivalence of malpractice, which will sadly result in new infections, drug resistance, and serious side effects among many, many people," Michael Weinstein, president of the AIDS Health Foundation, says in a news release. The AHF provides AIDS health care in 26 nations.

Other AIDS groups feel differently. The Black AIDS Institute supports the use of PrEP, as does Fenway Health, a provider of health services to Boston's lesbian, gay, bisexual, and transgender community.

"This approach can prevent many new infections and could dramatically impact HIV transmission worldwide as part of the tools we have available to stop the epidemic," Fenway medical director Kenneth H. Mayer, MD, says in a news release.

Last May, an FDA advisory panel voted in favor of approving Truvada for PrEP. The panel voted overwhelmingly to approve PrEP for men who have sex with men and for uninfected partners of HIV-infected people. But the panel approved Truvada PrEP by only a 12-8 vote for others at risk of HIV infection.

Birnkrant noted that the FDA approval comes with a risk-reduction program. Doctors prescribing Truvada PrEP must ensure that patients test negative for HIV before taking the drug. New tests are advised every three months at least.

In addition, people must be monitored for signs of kidney or bone problems -- which are among the long-term side effects sometimes seen with Truvada.

And the FDA says it will stay in close touch with those prescribing and taking Truvada PrEP to fine-tune the risk-reduction program.

"Education is the key," Birnkrant said. "We are committed to working with our public health colleagues to learn how best to use Truvada for PrEP so we can fully achieve the public health benefit it represents."

Truvada costs about $1,100 a month. It's not yet clear whether Truvada PrEP will be covered by insurance.