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Doctors now have another weapon against HIV/AIDS in their arsenal, and it’s a potent one. For the first time, the U.S. Food and Drug Administration (FDA) approved a drug treatment that will prevent infection in healthy people.

The drug, called Truvada, which is already approved for the treatment of HIV in infected patients, works by lowering the amount of virus circulating in people’s blood. But clinical trials show that it can also protect uninfected high-risk people from acquiring the virus, if they take the drug daily before and after exposure.

The approval is controversial. Some public health experts argue that allowing the drug to be used for prevention will foster a false sense of security among users, leading people to believe mistakenly that they are immune to the virus and reduce their use of condoms. However, the FDA determined that the benefits of expanding the pool of people who may use Truvada to protect against HIV made it worth approving. Here’s what you need to know.


Who can take Truvada?
The drug, made by Gilead Sciences Inc., is approved for healthy, uninfected people who are at high risk of contracting HIV through sex. These include sex workers and people with partners who are HIV-positive or engage in high-risk behaviors, such as using IV drugs.

How effective is the drug in preventing HIV?
In one study, healthy gay and bisexual men who took Truvada daily and were counseled about safe sex practices lowered their risk of becoming infected by up to 42%. In another study involving heterosexual couples in which one partner was HIV-positive, the uninfected partner had a 75% lower risk of contracting HIV if they took Truvada.

Does Truvada cure AIDS?
No. The drug can treat people who are infected with HIV by lowering the amount of virus in their bodies and slowing down the progression of the disease. In healthy, uninfected people, the drug can thwart HIV’s ability to take hold in healthy cells and start an infection, by blocking the activity of an enzyme that the virus needs to replicate.

Why is the approval controversial?
Some experts believe that healthy people may not take the drug correctly — it needs to be taken daily to be effective — which would encourage HIV to become resistant to the medication. Public health officials also worry that people may engage in more risky behaviors when they are on the drug, believing they are protected completely against HIV, which they are not. However, patients who receive Truvada prophylactically will be expected to participate in a comprehensive HIV protection plan involving regular HIV testing, condom use and prevention counseling and support. Clinical trials have not shown that users are more likely to engage in risky sexual behavior.

Researchers also can’t explain why in one study involving female sex workers, those who took Truvada to prevent HIV were not protected against infection. The authors think that the participants did not take the drug in the right doses, but it’s also possible that something about the vaginal environment makes the drug less effective.

(MORE: A Trial of an Anti-HIV Gel in Women Is Halted)

Why is the approval important?
Approving a drug to prevent HIV marks a big step toward controlling the spread of HIV and AIDS, not just in the U.S. but worldwide as well. Once Truvada is used as a preventive measure domestically, U.S.-backed AIDS programs in the developing world may also begin to roll out the pill for healthy people who are at high risk of contracting HIV. Public health experts are eager to build up all effective prevention strategies, noting that the only way to stop the epidemic is by preventing new infections as well as treating existing ones.
