HIV PrEP and PEP: Who Should Take Them, How Well They Work, and When to Start

PrEP and PEP are medicines that prevent HIV, used in different situations:

PrEP

If you're exposed to HIV while taking PrEP, the medicine can stop the virus from taking hold and spreading through your body.

Consider PrEP if you don't have HIV and:

• you've had anal or vaginal sex in the past 6 months and have a partner with HIV, haven't consistently used condoms, or were diagnosed with a sexually transmitted infection (STI) in the past 6 months
• you inject drugs and share needles or equipment, or have an injection partner with HIV
• you've been prescribed PEP and still engage in high-risk behavior, or have used several courses of PEP

If your partner has HIV and you're thinking about getting pregnant, ask your provider about PrEP: it may help protect you and your baby while you try to conceive, during pregnancy and while breastfeeding.

How well it works: taken consistently, PrEP cuts the risk of HIV from sex by about 99%, and from injecting drugs by at least 74% — but it's much less effective if doses are missed.

• PrEP doesn't protect against other STIs, so still use latex condoms every time — or polyurethane ones if you or your partner is allergic to latex.
• You'll need an HIV test every 3 months while taking it.
• Talk to your provider if taking it daily is hard, or if you want to stop.
• Side effects such as nausea are usually mild and often fade; report any that bother you or don't go away.

PEP

If you're HIV-negative and think you've recently been exposed, contact your provider or go to an emergency room right away. You may be prescribed PEP if you're HIV-negative or don't know your status and, in the past 72 hours, you may have been exposed:

• during sex — for example, a condom broke with someone who could have HIV
• by sharing needles or drug preparation equipment
• through sexual assault

Health care workers may also get PEP after a possible exposure at work, such as a needlestick.

Start it fast. PEP must begin within 72 hours (3 days) — the sooner the better; every hour counts. You'll take it daily for 28 days and see your provider during and after for HIV testing and other tests.

• Side effects such as nausea are usually mild.
• PEP can interact with other medicines, so tell your provider everything you take.
• PEP isn't for regular use. If you're often exposed — for example, frequent sex without condoms with a partner who has HIV — ask your provider about PrEP instead.

Sources

Based on "HIV: PrEP and PEP," MedlinePlus, U.S. National Library of Medicine; a work of the United States government in the public domain.