On Monday, the US Food and Drug Administration approved Truvada, the first medication intended to prevent HIV infections in people having sex with infected individuals.

When taken daily, Truvada (emtricitabine/tenofovir disoproxil fumarate) reduced the risk of HIV infection by 42 percent compared with a placebo. That was in a clinical trial where HIV-negative individuals had unprotected sex with multiple partners, including some HIV carriers, according to the FDA. Another trial involving heterosexual couples where one partner was infected — and condoms were used routinely — found that Truvada reduced the risk of infections by 75 percent.

“The data clearly demonstrate that Truvada as pre-exposure prophylaxis is effective at reducing the risk of HIV infection acquired through sexual exposure,’’ said Dr. Connie Celum, a professor of global health and medicine at the University of Washington who led the trial involving heterosexual couples. “It is exciting to consider the potential impact of this new HIV prevention tool, which could contribute to significantly reducing new HIV infections as part of a combination HIV prevention strategy.’’


Truvada is already approved to be used in combination with other antiretroviral drugs for the treatment of HIV.

For prevention purposes, the drug should be used along with other prevention methods, the FDA said in a press statement, such as safe sex practices, risk reduction counseling, and regular HIV testing.

“Today’s approval marks an important milestone in our fight against HIV,’’ FDA Commissioner Dr. Margaret Hamburg said in a statement. “Every year, about 50,000 U.S. adults and adolescents are diagnosed with HIV infection, despite the availability of prevention methods and strategies to educate, test, and care for people living with the disease.’’

The most common side effects reported with Truvada included diarrhea, nausea, abdominal pain, headache, and weight loss. In rare cases, the drug may cause kidney problems or bone toxicity.

As a condition of approval, the FDA is requiring Truvada’s manufacturer, Gilead Sciences, to study those who acquire HIV while taking Truvada to determine if anyone can develop a resistance to the drug. The company also needs to collect data on women who become pregnant while taking the drug since safety risks to the fetus remain unknown.

Truvada is expected to cost at least $13,900 a year for treatment in the U.S., according to Gilead Sciences.