HIV in Canada: A primer for service providers

Post-exposure prophylaxis (PEP)

Key Points

  • Post-exposure prophylaxis (PEP) is the use of antiretroviral drugs after an exposure to HIV, to reduce the risk of HIV transmission.
  • PEP works by helping to prevent replication of the HIV virus once it has made its way into the body.
  • PEP can reduce the risk of HIV transmission by over 80% when used consistently and correctly.

Post-exposure prophylaxis (PEP) is the use of antiretroviral drugs after an actual or suspected exposure to HIV to reduce the risk of HIV transmission. It should be started as soon as possible after a real or suspected HIV exposure but definitely within 72 hours. A combination of  three antiretroviral drugs is generally prescribed for PEP use. These medications must be taken every day for four weeks.

PEP works in an HIV-negative person after HIV has made its way into the body. If this happens, the medications in PEP may prevent the virus from multiplying and spreading throughout the body.

Research has found that PEP can reduce the risk of HIV infection by over 80%. We know that people can sometimes become infected with HIV despite taking PEP, and that PEP is most likely to work when used consistently and correctly. Factors that can limit the effectiveness of PEP include: low adherence to the full four-week course of pills, later PEP initiation, and continued exposures to HIV while taking PEP (PEP is only meant to reduce the risk from a single exposure).

The potential risks of PEP include drug toxicity and side effects, interactions with other medications, and the development of drug-resistant strains of HIV (if infection occurs). A person who wants to use PEP will have their HIV risk assessed, because PEP is only meant to be used after a potential high-risk exposure. A person will also be tested for HIV to confirm that they are HIV negative.


Post-Exposure Prophylaxis for Prevention (PEP)

Post-exposure Prophylaxis (PEP) – CATIE fact sheet

Can we prevent infection with HIV after an exposure? The world of post-exposure prophylaxis (PEP)Prevention in Focus

The PEP Program at Clinique l’Actuel Programming Connection

Updated Guidelines for Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV—United States, 2016 – U.S. Centers for Disease Control and Prevention (CDC)



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