A highly effective once-a-day pill for preventing HIV has been available in the United States since 2012—but you've probably never heard of it.
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A highly effective once-a-day pill for preventing HIV has been available in the United States since 2012—but you've probably never heard of it.

That's because just 1% of people who could benefit from the medication are actually taking it, and a third of primary care doctors and nurses don't know about it, according to the U.S. Centers for Disease Control and Prevention (CDC).

The medication, Truvada, is a “huge” step in the fight against AIDS, according to Susan Buchbinder, MD, the director of Bridge HIV, an arm of the San Francisco Department of Public Health dedicated to HIV prevention, research, and education.

“It's a highly effective tool and we really do need to get it out to the people who most need it,” Dr. Buchbinder says. Here are the facts about this breakthrough drug.

How does Truvada work?

Truvada is a combination of two HIV drugs, emtricitabine and tenofovir, which block an enzyme that the virus needs to make copies of itself. Taking the medication daily will flood the mucosal membranes with these HIV-fighting molecules, preventing the virus from spreading through sexual contact.

Researchers are looking into whether other approaches to dosing are equally effective. A brand new study in the New England Journal of Medicine suggests that taking Truvada before and after sex might be equally effective. The researchers enrolled 400 men at high-risk of contracting HIV to the trial, randomly assigning half of them to a placebo group. Each participant was instructed to take the medicine 2-24 hours before sex, and then again within 48 hours after sex. (All were also told to use condoms and practice safe sex). In the end, the men who took Truvada were 86 percent less likely to contract HIV than those in the placebo group.*

Who should be taking it?

The drug is an option for people with a very high risk of HIV infection due to their sexual activity or drug use. For example, a person with an HIV-positive partner or someone who uses injection drugs can reduce their risk of contracting the virus by 70% to 90% if they take Truvada daily. The CDC reckons that one in four sexually active men who have sex with men, one in five injection drug users, and one in 200 sexually active heterosexual adults are candidates for the treatment, also known as pre-exposure prophylaxis (PrEP).

Are there any risks?

“We talk about PrEP not being a lifelong preventive approach, but rather it's used during what we call 'seasons of risk,'” like when you're dating an HIV-positive person, or perhaps you're newly single, Dr. Buchbinder explains. People who are on Truvada need to visit their health care provider every three months, in part so that they can be tested for HIV. An HIV-positive person should not be on Truvada, because taking the drug can lead to resistance. It's also recommended that people also use other HIV prevention methods, including condoms, while taking the drug.

“The other big concern with this drug is really about kidney function,” Dr. Buchbinder explains. “It can't be taken by people who have pretty severely impaired kidney function, and also kidney function needs to be monitored over time.”

How much does it cost?

A year's worth of Truvada costs about $10,000, and expenses for the required quarterly medical visits and lab tests also add up—another part of the reason why few people take it. But many insurers help cover these costs, and Gilead (the company that manufactures the drug) offers a patient assistance program to help people who can't afford the medication.

Many experts say the expense is worth it if you have high risks. "We know if we prevent an infection, it saves $350,000 over a lifetime for a person in health costs, so it’s definitely an economically sound approach,” Anthony Fauci, MD, the director of the National Institute on Allergy and Infectious Diseases, told Time earlier this year.

As Dr. Buchbinder put it, at the end of the day, what's most important is "for people to know that if they're at-risk now we have something that's very highly effective and that they should talk to their provider or doctor about.”

*This information has been updated.