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PEP (Post-exposure prophylaxis)

This answers frequently asked questions about HIV PEP (Post-exposure prophylaxis).

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HIV PEP (Post-exposure prophylaxis) is the use of antiretroviral drugs as soon as possible after a high-risk exposure to HIV. Antiretroviral drugs combat HIV infections by attacking the virus' DNA. It helps to reduce (but not eliminate) the possibility of HIV infection. If you have a significant exposure to HIV, the sooner you can start PEP, the better! Contact a healthcare provider as soon as possible after exposure to find out if PEP is right for you.

The basics

Who should take PEP?

PEP is only recommended for people with high risk exposures to HIV that have occurred within the past 48 hours. A high risk exposure would include:

  • Unprotected vaginal or anal sex with known (or likely) HIV positive partner
  • Injection drug use needle exposure
  • After a sexual assault
  • Non-intact skin (open cut or wound) or mucus membrane (eyes, nose, mouth, etc.) contact with blood

How do you use PEP?

PEP is a four-week program of two or three antiretroviral medications, several times a day. The medications have serious side effects that can make it difficult to finish the program. Treatment should be started as soon as possible, preferably within the first several hours after an exposure. It should be administered within 48 hours of a high-risk exposure (not to exceed 72 hours). After 72 hours PEP is much less effective in preventing HIV infection. The sooner PEP is administered, the more effective it is.

Can anyone use PEP?

PEP is only for situations right after a potential HIV exposure. PEP does not replace regular use of other proven HIV prevention methods. If you get PEP, you will need to return for HIV testing at 4 to 6 weeks, 3 months, and 6 months after the potential exposure. Because PEP is not always effective, continue to use condoms and/or dental dams with sex partners while taking PEP. Never share injection equipment with others.

Does PEP have any side effects?

PEP is safe, but it may cause nausea and other side effects such as diarrhea and headaches in some people. 

Where can I get PEP?

Your primary care provider, emergency rooms, or urgent care clinics may be able to provide PEP. Remember, if you have significant exposure to HIV, get medical follow-up right away. If you do not have a healthcare provider, contact the Mayor's Health Line at 617-534-5050 for help in finding care in Boston.

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