PEP and PrEP

PEP stands for Post Exposure Prophylaxis.  PrEP stands for Pre-exposure Prophylaxis


PEP is a combination of HIV drugs which can be used to reduce the likelihood of a HIV negative person getting HIV after they have been exposed to the virus.  PEP needs to be prescribed, and can be obtained from A&E departments or sexual health clinics.  PEP needs to be taken as soon after exposure as possible to increase its chances of working effectively.  In the UK, PEP can be taken up to 72 hours after exposure.  However, it is much less likely to be effective when used this late.



PEP is not a single tablet. It is a combination of three HIV drugs which need to be taken for 28 days.  The principle behind PEP is that the very early use of HIV drugs may stop HIV from establishing itself in the body.

Before you start PEP, you will be asked to take a HIV test.  This test is used to ensure that you are not already living with HIV (from a previous exposure).  It is important to know that the test will tell you nothing about the most previous exposure.  If the test comes back positive, you will not be prescribed PEP because a short course of HIV treatments may result in drug resistance developing.



After a course of PEP, you will have to wait at least 28 days before having another HIV test. This is because PEP may delay the HIV infection and so a test at the end of the course may not give an accurate result.



The drugs used for PEP are the same drugs used for HIV treatment.  Some people who are living with HIV will be taking the same combination.  Like many drugs, PEP may have some side effects.  Side effects may include fatigue (tiredness), vomiting, headaches and diarrohoea.  However, not everybody will experience side effects and, unfortunately, you will not know until your start taking the drugs whether they will affect you in this way.  What we do know is that side effects are usually short-term whilst the body is getting use to the presence of the drugs.



PrEP stands for Pre-exposure Prophylaxis and allows people to take anti HIV medication (Truvada) daily, or before sex, in order to prevent HIV from being able to take hold in someone’s body if they are exposed to it.  This is an exciting development in HIV prevention and studies undertaken so far do indicate that PrEP is successful in preventing HIV infection in most settings.  PrEP is not currently available in the UK outside of a clinical trial setting, but work is ongoing and this may change.


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