HIV Post Exposure Prophylaxis (PEP)


Post Exposure Prophylaxis (PEP) is the administration of antiretroviral HIV medications for 28 days, commenced within 72 hours of possible exposure to HIV infection.

Does it work?

PEP has been shown to reduce the risk of HIV infection following needle stick injuries to healthcare workers by 81%.  However, it is unknown whether it is effective following sexual exposure, though animal and laboratory studies suggest that it is likely to be.


Individuals who believe they may have been at risk of acquiring HIV infection following recent sexual exposure should discuss PEP with a doctor or nurse who can assess the risk and arrange PEP if it is considered advisable. An example of a risky sexual exposure could include condomless sexual intercourse with a person known to have HIV and who is not taking HIV medication.

If your risk is considered to be high PEP will generally be recommended. In other situations (e.g. a broken condom during heterosexual intercourse), the very low risk of HIV infection has to be balanced against the significant risk of side effects of medications, and PEP may not be recommended.

Initially, you will have baseline blood tests and swabs for HIV and other infections. You will then be given a four weeks supply of PEP medication. If your partner is HIV positive, it is useful to know what medication they are taking to help determine the best PEP medications for you.

You will receive a text within one week for a negative HIV test and a call if any of your swabs are positive. You will then be asked to attend the centre again in 6 weeks, for repeat blood tests.

HIV testing will be then be repeated 3 months after exposure.
It is important to take all tablets you are given as directed. If you miss doses, PEP is less effective.

  • PEP should be commenced as soon as possible after potential exposure, within 72 hours.  
  • PEP is not a 'morning after pill' and does not replace the need for safe sex practices. We do not know how effective it is!
  • PEP is not easy to take. Nausea, headache and diarrhoea are common side effects of HIV medications and may be severe.
  • Safe sexual practices are essential until final testing at 3 months after exposure.
  • Medications and testing are provided free of charge at MSHC. 

This fact sheet is designed to provide you with information on Post Exposure Prophylaxis (PEP). It is not intended to replace the need for a consultation with your doctor. All clients are strongly advised to check with their doctor about any specific questions or concerns they may have. Every effort has been taken to ensure that the information in this pamphlet is correct at the time of printing.
Last Updated June 2018