What you need to know about emergency PEP: Post-Exposure Prophylaxis

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PULSE Clinic

PULSE Clinic

Established in Bangkok, PULSE Clinic is a gay-owned private clinic whose mission is to promote and provide excellence in standards of care and education in sexual wellbeing, HIV and related infections, and to actively engage in the formulation of public health policy and research, with the aim of reducing HIV disease burden worldwide.


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If you have had a high-risk exposure to HIV in the last 72 hours, you may want to consider taking PEP. However, your treatment must be started within 72 hours after a possible exposure to HIV.

It is most effective when started within 24 hours. The sooner someone starts PEP, the better the prevention. 

You may be a potential candidate for PEP if any of these factors apply to you:

  • The partner is known to be HIV positive AND is not on treatment.
  • Anal sex with penetration without condom
  • Vaginal sex without condom
  • Condom break
  • Presence of blood
  • Presence of cuts or ulcers
  • You are not circumcised
  • You have been exposed to potentially HIV infected body fluids
  • Your exposure was less then 72 hours ago
  • Partner of unknown HIV status who belong to higher risk HIV group (e.g. MSM or from Africa or Southeast Asia)
  • They penetrated you (Their penis, your arse) and you don’t know for sure whether they have HIV or not.

However, if you are unable to access PEP within the 72 hours, even if it has been up to 5-7 days since the exposure occurred, it is still worth seeking medical advice to see what your options are.

This may include commencing a 3-drug combination of antiretroviral medications as soon as possible just in case you have become HIV positive. In this case, you would be starting very early treatment and minimising the damage to your immune system.

How does PEP work?

It takes a few days for HIV to become established in the body following exposure. Once it is established you will have HIV for the rest of your life. However, if you begin taking PEP in time, the anti-HIV drugs will prevent the HIV (that’s already in your body) from reproducing and it DIES out before it has a chance to multiply. PEP drugs given at this time may help the body’s immune system to stop the virus from replicating (multiplying) in the infected cells of the body. The cells originally infected would then die naturally within a short period of time without producing more copies of HIV.

If the virus is already in my body, is it too late?

Not if you act quickly. After HIV gets in the bloodstream it takes some time before it permanently establishes itself in the body. If a person who has been exposed to HIV acts quickly to get PEP (within 72 hours) they stand a good chance of stopping the virus from establishing itself in their body.

So, if I take PEP, I won’t be HIV positive?

Research indicates that taking PEP makes infection with HIV a lot less likely. But PEP doesn’t work every time – some people who take it still end up with HIV afterwards. It can fail because:

– the person doesn’t or isn’t able to take PEP as prescribed (every day for a month)

– some anti-HIV drugs don’t work against some strains of HIV (HIV drug resistant, although this is rare)

– the initial viral load (the amount of HIV) in the body was too great for the drugs to be effective

However, the sooner PEP treatment is begun after exposure to the virus, the more likely it is to work.

What HIV PEP drugs are the most common?

Doctors tend to favour PEP medicines with fewer side effects and better HIV prevention, which will be taken for 28 days. For adults: Tenofovir combined with either Tenofovir (TDF) and emtricitabine (FTC) as preferred backbone drugs and these are also the preferred drugs for treating HIV. The recommended third drug, which is also recommended by WHO and CDC as a preferred drug for HIV treatment, will be chosen by your doctor.

There are some of our clients who do not understand when our doctors try to explain about HIV drug resistant. If you are unlucky and being exposed to such HIV, the classic PEP medications are not able to help you. That’s why American CDC suggested on their PEP treatment guidelines that doctors should use a higher class of drugs that is less likely to be resisted by the HIV drug resistant type.

These higher class medications are available at clinics but they are costly – much more expensive than the classic PEP medications generally used in low income countries. When doctors prescribe this higher class PEP medications it is because they evaluate that your risk is very high and they are trying to keep the standard as high as American Center of Disease Control Guidelines for PEP treatment.

What else can be done?

Your doctor might advice that you get treatment as prevention for possible gonorrhoea/chlamydia/syphilis after unprotected sex or sexual accident.

You don’t need PEP if…

– You are confident that your partner doesn’t have HIV.

– The partner is HIV positive and on successful treatment (Known as ‘undetectable viral load’).

– Human bites

– Another person’s semen gets in your eye.

What will the doctor ask me?

The doctor will try to evaluate how likely it is you have actually been exposed to HIV before starting treatment. Questions will include what happened to make you think you’ve been exposed to HIV, what sort of sexual or injecting activity or partner is likely to be HIV-positive.

We will ask you things like if you know whether the person has HIV (and if they are HIV-positive, if you know if they have an undetectable viral load), and in the case of a possible exposure through a sexual encounter, we will ask about things like: the kind of sex you had (e.g., anal, vaginal or oral sex); if you fucked them or they fucked you; if either of you came inside the other; and if there is anything else you are worried about.

It is important to be honest and accurate in providing this information – doctors are there to help you, not to judge you, and the information will help us to assess the seriousness of the situation.
The risk of getting HIV from oral sex is extremely low. PEP is not recommended after possible exposure to HIV through oral sex. The only exception would be following receptive oral sex from a partner known to have HIV and when the receptive partner has cuts or lesions such as ulcers in their mouth.

What are some side effects?

With the new PEP drugs we use, side effects are very rare. Fewer than 1 in 100 of our patients actually develop any side effects. Common side effects (<1%) include nausea, diarrhoea and feeling tired. Rash and fever are uncommon (< 0.1%) side effects.

How can I remember to take my PEP?

Here are a few tips that may help you remember to take PEP each day for the month:

– Set a daily alarm or reminder on your mobile phone to remind you to take your medications.

– Take your drugs at the same time each day (e.g., after breakfast, after dinner).

– Put your PEP drugs near something you use daily, as a reminder.

– Take your medications at the same time you brush your teeth – and place the medications near your toothbrush so you will notice them.

– Keep a post-it-note attached to your fridge or noticeboard with the letter ‘P’ on it; this will be a discreet reminder to you to take your drugs.

– If you are planning a big night out, carry enough of your PEP drugs to take in case you don’t make it home.

– Get someone you trust to remind you to take your medications.

What about taking other drugs while on PEP?

PEP can interact with other drugs (including other prescription drugs, supplements and vitamins) and change the way the PEP drugs work. Taking recreational drugs while on PEP can be risky. Recreational drugs can have severe side-effects in combination with some of the PEP drugs. Talk to the doctor or nurse who prescribes you PEP about any other prescription or recreational drugs you may be taking or planning to take. If you wish to take recreational drugs while on PEP, talk to the doctor who prescribed you PEP.

I’ve finished my 28-day course of PEP. What’s next?

Once you’ve finished the course of PEP, see your provider or come back to us to get tested for HIV, the doctor will evaluate your risks and might recommend you to start taking PrEP. You should get tested again 3 months after you have finished the PEP to confirm your status.