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CHAPS PEP booklet
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PEP: THE BASICS

Heard about PEP?

PEP stands for Post Exposure Prophylaxis and is a treatment that may prevent HIV infection after the virus has entered the body.


Post
=
After
Exposure
=
A situation where HIV has a chance to get into someone's bloodstream, like unsafe sex
Prophylaxis
=
A treatment to stop an infection happening

PEP treatment:

  • Involves taking anti-HIV drugs for four weeks
  • Must be started as soon as possible after unsafe sex or a condom not working, straight after exposure or within 24 hours is best and no later than 72 hours (three days)
  • Has side effects
  • Is likely to stop HIV but isn't guaranteed to work

Where do I get PEP?

  • Sexual Health clinics (GUM or 'clap' clinics)
  • Hospital Accident & Emergency departments (A&E)
  • Not all of these places in every part of the country will have PEP or be able to prescribe it
  • GPs won't usually be able to prescribe PEP

How soon?

It is best to start PEP straight after exposure or within 24 hours and no later than 72 hours (three days) later. The longer you wait there is less chance it will work, after 72 hours PEP isn't usually given as it's unlikely to work by then.

But if HIV is in my body doesn't this mean I will now be infected?

No. After HIV gets into your bloodstream it takes from a few hours to a few days before it permanently infects you. If you act in that short time you stand a chance of stopping HIV before the infection takes hold.

How does PEP work?

Taking two or three anti-HIV drugs every day for four weeks might stop the HIV before it gets a permanent hold in your body. PEP is not a 'morning after' pill that's taken just once, it's one month of drug treatment.

So if someone takes PEP they won't become HIV positive?

Research shows PEP makes infection with HIV a lot less likely. But PEP doesn't always work, some people who take it still end up with HIV after treatment. PEP can fail because some anti-HIV drugs don't work against some strains of HIV. It's more likely to fail if it's not taken properly or soon enough.

Are the drugs the same as the ones taken by people with HIV?

Yes, you take three drugs which are also used in 'combination therapy' taken by HIV positive people.

Is PEP a cure for HIV?

There is no cure for HIV. PEP can only stop HIV infection if it's taken very soon after it has entered your body and before the infection takes hold. Once HIV infection becomes permanent then anti-HIV drugs can't get rid of the virus. This is because it is now in parts of the body the drugs can't reach. Once HIV permanently infects you the drugs can usually control the HIV in their body but can never get rid of it completely.

Does PEP have side effects?

Yes, it can cause diarrhoea, headaches, nausea and vomiting. Because of the side effects, you may need time off work or study and some people have to stop taking it. Side effects go once you stop taking the drugs. One Australian study showed that among people taking PEP, side effects were mild to moderate for two out of three people and severe for one in four.

We had unsafe sex... The condom broke... Is it worth asking for PEP?

Use our self-assessment tool to help work out your risk of getting HIV and whether it's worth asking for PEP.

To speak to someone in person, call THT Direct on 0808 8021221 for more information on PEP and where to get it.

What are the chances someone will get PEP?

New guidelines have been given to Sexual Health Clinics that help doctors decide if PEP should be given. A doctor will need to ask questions about what kind of sex happened, when and who with.

It’s worth thinking about PEP if you or someone you had anal sex with didn’t use a condom or something went wrong with the condom and it’s not later than 72 hours (3 days) since it happened. Doctors might sometimes give PEP after oral sex, depending on the circumstances.

What are the chances I will get PEP?

Doctors have guidelines to help them decide whether PEP should be given, they will need to ask questions about:

  • Who you had unsafe sex with, to identify their likelihood of having HIV.
  • What kind of sex you had, when it happened, whether it was oral or anal sex, who fucked who and whether either of you came inside the other. Doctors might sometimes give PEP after oral sex, depending on the circumstances.

They will also talk to you about having an HIV test. Before you are given PEP you must have a test to check you don't already have HIV. You must also agree to be tested after taking PEP to see if it's worked. PEP won't be offered if you refuse to be tested.

What if I can't get to a place that has PEP within 72 hours?

After 72 hours PEP won't usually be offered so if it's not possible to get to a Sexual Health Clinic in time it is advisable to go to a hospital Accident & Emergency department because they never close.

If I take PEP can I become resistant to HIV drugs so they won't work if I later get HIV?

No, it's HIV, not your body that can become resistant to the drugs. If PEP works it gets rid of the virus - and the virus can't become resistant because it's not there anymore. So if you were to become HIV positive later and needed drugs it wouldn't make any difference that you took PEP in the past.

But if PEP doesn't work and you become HIV positive, there may be problems with the HIV in your body being resistant to some drugs, including ones used in PEP.

If I'm taking PEP does that make me immune to HIV while I'm on it or when I've stopped taking it?

No. Unsafe sex while taking PEP could let more HIV into your body, making PEP much more likely not to work.

If, after taking PEP you have stayed HIV negative and then you have unsafe sex again, you can become infected just like any other HIV negative person.

Now we have PEP does it matter so much if I don't use condoms?

PEP doesn't change the need for condoms, here's why:

  • Using a condom is more likely to stop HIV being passed on than PEP is.
  • Condoms don't make you ill with side effects, which PEP can.
  • You need a condom for as long as the sex lasts - but PEP lasts for four weeks.
  • Condoms are everywhere. PEP can be hard - sometimes impossible - to get.
  • You control getting hold of condoms but doctors decide if you should get PEP and they may say no.

How many times can I have PEP?

Doctors decide who gets PEP and they're unlikely to give these expensive and powerful drugs to the same person time after time. So if you keep having unsafe sex you will usually be offered help with having safer sex rather than being given PEP lots of times.

Much of the information on this page has come from the British Association for Sexual Health and HIV (BASHH) Patient Information Sheet.

  • This article was last reviewed on: 11/10/2011
  • Date due for next review: 11/10/2013

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