Pre-exposure prophylaxis (PrEP) is an HIV prevention strategy where HIV-negative individuals take anti-HIV medications before coming into contact with HIV to reduce their risk of becoming infected. The medications work to prevent HIV from establishing infection inside the body.
PrEP has been shown to reduce risk of HIV infection through sex for gay and bisexual men, transgender women, and heterosexual men and women, as well as among people who inject drugs.
It does not protect against other sexually transmitted infections (STI) or pregnancy. It is not a cure for HIV.
Post-exposure prophylaxis (PEP) is an HIV prevention strategy where HIV-negative individuals take HIV medications after coming into contact with HIV to reduce their risk of becoming infected. PEP is a month-long course of drugs and must be started within 72 hours after possible exposure.
PrEP has been shown to help reduce HIV infection risk in multiple studies. The iPrEx trial showed that PrEP reduces the risk of HIV infection among gay and bisexual men and transgender women. Two large trials, Partners PrEP and TDF2, showed that PrEP also reduces the risk of HIV infection among heterosexual men and women. The Bangkok Tenofovir Study demonstrated that PrEP works for people who inject drugs.
The U.S. Food and Drug Administration (FDA) approved Truvada for PrEP use in 2012. This medication is taken as a once-daily oral pill, which combines two medicines in one: Emtriva (also called emtricitabine or FTC) and Viread (also called tenofovir disoproxil fumarate or TDF). Truvada works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
Other anti-HIV drugs are also currently being studied for PrEP, to provide a wider array of options. They have not yet been shown to be effective for PrEP, nor have they been FDA approved. However, trials are currently underway to determine if they are effective and in a few years we will know more. These drugs include:
MARAVIROC (also called Selzentry or MVC):
This medication is taken as a once-daily oral pill and works by blocking entry of HIV into the body’s cells.
RILPIVIRINE (also known as Edurant):
This medication is injected once a month as a long-acting formulation and works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
DAPIVIRINE (also known as TMC120):
This medication is released by a vaginal ring that is worn for four weeks at a time. The medication works by binding to and disabling an enzyme called HIV reverse transcriptase. By disabling this enzyme, it prevents HIV from making more copies of itself in the body.
TENOFOVIR (also known as tenofovir disoproxyl fumarate, TDF, or Viread):
This medication is one part of the already approved combination pill Truvada. By itself, it is currently being studied as part of a microbicide gel to be inserted rectally and/or vaginally. Tenofovir works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
Truvada for PrEP provides 92%-99% reduction in HIV risk for HIV-negative individuals who take the pills every day as directed. If a daily dose is missed, the level of HIV protection may decrease. It only works if you take it. People who use PrEP correctly and consistently have higher levels of protection against HIV.
According to data analysis from the iPrEx study that found PrEP to be effective:
There are not enough data available to provide specific timing guidance on non-daily use, so the FDA recommends PrEP be used daily to achieve the highest level of protection.
A few things to note:
Truvada for PrEP is generally safe and well tolerated. Most people on PrEP report experiencing no side effects, but some side effects were reported in clinical trials. Participants in the iPrEx study reported side effects that fall into four main categories (ordered here as most to least common):
For most people, these side effects went away on their own after the first few weeks of taking Truvada, or when the medication was stopped.
Truvada for PrEP is taken once a day, at the same time each day. You can take it with or without food. In order to benefit from this medication, adherence is critical.
(If you need help keeping up with your medication, check out this handy resource.)
You need to see a doctor for a prescription or join a PrEP research study. If you’re interested in learning more on how to access PrEP, visit this section.
Prices for the medication can be as low as $0 or as high as $2,000 per month depending on whether you have health insurance and/or if you’re enrolled in a research study. If you’re interested in learning more about co-pays and how to potentially get your medication for free or at low cost, visit this section.