PrEP, PEP and PEPSE
This page includes links to information about PrEP, PEP and PEPSE.
PrEP = Pre Exposure Prophylaxis.
It is the term for using HIV drugs before and after sex.
If taken as recommended, PrEP is highly effective at preventing HIV infection. It will reduce the chance of getting HIV by at least 99.99%.
PrEP is pill, usually taken daily. Some people (mainly cisgender men) can use event-based dosing. This involves taking only two pills before sex, another after 24 hours and another after 48 hours.
PrEP uses two HIV drugs in one pill before (and after) exposure. This is usually tenofovir disoproxil (TD) and emtricitabine (FTC).
See: UK guide to PrEP
PEP = Post Exposure Prophylaxis.
It is the term for using HIV drugs after a high risk exposure to reduce the chance of an infection. I can refer to any type of risk, for example, after a needle stick injury or after sex.
PEP involves taking a combination of three HIV drugs every day for one month. After this month you need to wait 4 to 6 weeks before an HIV test will be effective.
PEP needs to be taken as soon after sex as possible, ideally within the first few hours. In most countries PEP is only available within 48 hours of having sex. In a few countries, including the UK, PrEP can be prescribed up to 72 hours (three days) after.
PEP has NO effect if taken more than three days after sex.
PEP is not prescribed in the UK unless there is a real risk of HIV.
Anyone using PEP delays the time until they can take an HIV test. Remember that HIV test only tell you your HIV status 6-8 weeks ago. So to know whether or not PEP worked, you need to wait 6-8 weeks after the last PEP dose.
This is because if the PEP drugs do not stop infection they will work against the new virus.
If you are using a 4th generation HIV test, then wait 6 weeks after your last PEP dose.
If you are using a 3rd generation HIV test, you need to wait 8 weeks after your last PEP dose before testing.
PEPSE = PEP after Sexual Exposure
This term is sometimes used in the UK when referring to PEP after sex.
For example if you didn’t use a condom or if the condom broke or came off and your partner is HIV positive and NOT on treatment.
PEPSE is used in the UK to separate this from exposure linked to your job – for example if a health worker has a needle or syringe injury.
Questions to i-Base about PEP and/or PrEP
The i-Base Q&A service has been asked many questions about PEP.
These are links to some of the questions answered online.
- How do I safely use PreP if I buy it online?
- What is PEP? (Post Exposure Prophylaxis)
- I have started PEP and what to know if I will be okay?
- Does PEP have side effects?
- Does PEP extend the window period for testing?
- Other questions and PEP
- Other questions and PrEP
Links to more information and resources
i-Base guide to HIV transmission and testing
Articles from i-Base on reducing HIV transmission
Activists call for urgency of NHS access to PrEP (June 2015)
Q&A on PrEP in the UK and changes to the HIV PROUD study. (October 2014)
The little blue pill that can stop HIV: UK PROUD study (December 2013)
Online presentations on treatment as prevention – August 2011
US CDC issue preliminary guidance for use of PrEP – February 2001
PrEP reduces transmission in gay men at high risk: iPrEx study – December 2010
Links to other websites
UK guidelines on PEP (BASHH 2006) PDF file
This important edition of Research Initiative, Treatment Action (RITA!) interviews key researchers and features two comprehensive reviews of preexposure prophylaxis (PrEP).