Q and A


Should I keep a few pills in case I need PEP again in the future?

Is it a good idea to stop PEP on Day 26 and keep the 2 remaining Truvada and 4 raltegravir pills as “insurance” in case of a future mishap?

I ask because after a condom break and unverifiable HIV status of my sex partner, obtaining PEP was a miserable experience due to emergency room staffing shortages and my travelling.

Most of the stress was in this phase and should I ever need it again, I would like to be able to start within minutes, not after 28 hours. If not advisable, are there starter packs that can be obtained? I know all the stuff about liver testing and verifying HIV before treatment, but if I test negative and only have safe sex, the latter is pointless.

The liver testing could be done after a couple days I’m imagining (anyway, few side effects besides a bit of tiredness) Thanks for a practical answer.



Thanks, yes, the short answer is that there are lots of reasons why this might be a good idea and very few reasons not to consider this.

A slightly longer response continues…

There is actually very little data on the effectiveness of PEP. This is mainly because HIV is already such a difficult virus to catch, any study would need to include many thousands of PEP cases to start to see anything significant. So even though some PEP studies report low numbers of infections – often none – these studies usually only include a few hundred people when looking for something that might only have a 1 in 500 chance of occurring anyway.

The study I remember that showed a benefit used starter packs – and this has always made the most sense – especially if someone is at higher risk.

i-Base information always stresses the earlier PEP is started, the better chance it will work. This should ideally be within hours. On this basis, PEP clinics (including general hospitals) would be better to give someone a single Truvada tablet as soon as they walk through the door..

The single pill would start working immediately (FTC is absorbed very fast, tenofovir takes longer). This means PEP could start working while other tests are carried out. In the event that someone might already HIV positive, another med could be given to minimise any risk of drug resistance (ie switching to a boosted PI for two days). Another alternative would be an option to continue HIV treatment, which is increasingly an option on diagnosis.

There is no data to show there is any difference between 26 day or 28 days of PEP, so you can easily do this with little likely impact on the efficacy of PEP. Actually, there is no data showing a difference between 21 and 28 days either – I think 28 days was chosen for practical reasons as much as anything else.

In practice, after a needlestick risk. most health workers report stopping PEP within a week or two. This shows that even people who should be the best informed about PEP, often do not complete the full course. The full course is always recommended. 

Either way, holding back a few days of PEP does makes practical sense, especially when health services generally – certainly in the UK – keep people waiting for at least four hours, if not considerably longer. It would also take the uregency and panic out of getting PEP. so that if the incident happened at a difficult time, you could go to the PEP clinic the next morning.

You are right to be cautious about not using PEP in the future if you might become positive. You could explain all this to the clinic when you next need PEP.

There is little risk form a single dose of Truvada

An important caveat is that advocates at i-Base are not doctors. This practical information is just based on the theoretical mechanism for PEP and the difficulties in accessing PEP promptly.

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  1. Simon Collins

    Hi Mirriam, if you need PEP then it is best to take it as soon as you can. The sooner you start, the quicker it can start to work. Different countries use different tablets, but you need to include three active drugs. Sometimes this can be in a single pill.

  2. Mirriam

    After having unprotected sex,can I take pep immediately,?will it help me one tablet?

  3. Josh Peasegood

    Hi Francis, are you taking PEP or ART? In either case you should not stop. Continue the course of what treatment you are taking. While not ideal, missing a dose for 3 days it is possible there was still enough medication in the body to still work over this time.

  4. Francis

    I skipped dose for 3 days and continued
    Will it make any difference or should I just stop?

  5. Jack

    “In practice, after a needlestick risk. most health workers report stopping PEP within a week or two.”

    I could not find a single paper showing this. Do you have a source for this information? I am afraid a lot of the internet-educated self-proclaimed doctors are going to believe your words which is not backed by any evidence.

    People are going to believe you and break their PEP regime, Please be careful.

  6. Simon Collins

    Hi Jack,

    Thanks for your feedback – and I am sorry that you thought this info was suggesting stopping early.

    This isn’t the case. I was just report the fact that how adherence to PEP is often very low. This is even among health workers who should understand that needlestick risk can be higher than sexual risk. They should also understand the importance of completing a course of meds.

    Over the years, dozens of studies report such low adherence, maybe hundreds. Did you try Google?

    The three studies below from different setting are referenced in the i-Base guide to HIV testing and transmission:

    One reports that more than 4 in 5 health workers don’t complete the PEP course.

    Suglo RE et al. Predictors of adherence to HIV Post-Exposure Prophylaxis protocol among frontline healthcare workers at the Ho Teaching Hospital, Ghana. Int J Infect Dis. 2021 May;106:208-212. doi: 10.1016/j.ijid.2021.03.079.

    Lin C et al. Occupational Exposure to HIV Among Health Care Providers: A Qualitative Study in Yunnan, China. JIAPAC. doi: 10.1177/1545109707302089.

    Ford N et al. Adherence to HIV postexposure prophylaxis. AIDS: November 28, 2014 – Volume 28 – Issue 18 – p 2721-2727 doi: 10.1097/QAD.0000000000000505.

    I have clarified the post though to reduce the chance that people read this wrongly.


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