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 needlestick 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.


Anyone who believes that he or she may be at risk of acquiring HIV infection following sexual exposure should discuss PEP with a doctor or nurse who can assess the risk and arrange PEP if it is considered advisable. To be at risk of HIV you need to have had risky contact (eg penetrative sex, sharing a syringe) with a person who has HIV (eg gay man, someone who has lived in a high risk country).

If your risk is considered to be high (eg unprotected receptive anal male-male sex), PEP will generally be recommended.  In other situations (eg 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 be given a one week supply of HIV/PEP medication.  Your doctor will decide what medication(s) are most appropriate in your circumstances. If your partner is known to be HIV positive, it will be very useful to know what medication they are taking to help determine the best PEP medications for you.
We know that if PEP is going to be effective, it is important to take all the tablets you are given as directed. If you miss doses it will make PEP less effective.

You will have a follow-up appointment one week later.  At this visit, the blood test and swab results from the previous week will be available. 

Assuming your HIV test result was negative, at this point you will be given another 3 weeks supply of medication.  If you have been having significant side effects, the original medication(s) may be changed.

You will be asked to attend the centre again in 6 weeks, when blood tests will be repeated.

HIV testing will be repeated 3 months after exposure.

  • PEP should be commenced as soon as possible after potential exposure, and certainly 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 August 2017