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.

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 mightbecome 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. Josh Peasegood

    Hi Adrian, regardless of the combination, you have started PEP within 72 hours. PEP will have the same potency. It is best now not to switch back and remain on your current regimen for the remainder the course. Are you doing better on this combination?

  2. Adrian

    Hello, I had a possible high risk exposure and got pep within 12 hours but after 2days of consumption, I could no longer put up with the side effect of the medication I was given which was viraday. I went back to the same clinic and they prescribed me tenof-em and tivicay. I’m still well within the 72 hours period from exposure. Will switching meds now affect the potency of pep? Should I switch or remain on the previous drug and soldier on the side effects.

  3. Simon Collins

    Hi John, thanks, there are no problems taking PEP and COVID-19 vaccines at the same time. The caution is only about supplements, not foods that contain aluminium and magnesium. This is becasue supplements reach much higher levels.

  4. John


    I started PEP 2 days ago, 7 hours after possible exposure, I’m due to have my 2nd dose of the covid vaccine in a few days and wanted to know if the 2 will affect each other in any way?

    I haven’t seen any studies on this, also I see on the label of Raltegravir that Aluminium and Magnesium containing antacids shouldn’t be taken within 6 hours but what about foods containing high amounts of magnesium and aluminium like nuts, milk, etc and protein supplements like Whey. Do these affect the results of PEP or is it only antacids not any food?

  5. Simon Collins

    Hi Mila, you don’t say which country you are in. This might be important for advice about what to do now. Please contact the doctor that prescribed the PEP to talk about your response so far. They can also monitor and access the problems you report. They can also evaluate the risk with you of different options.

  6. Mila

    Hello I’m a health care worker and had a needle prik injury at work (the patients hiv status is unknown)
    I’ve been taking pep for 2 weeks now and it’s not been an easy journey.
    Lately I have been having kidney pain and it’s persistent through out the day- I know that pep can cause kidney impairment and was wondering if I should stop taking the medication as to preserve the health of my kidneys or I should continue?


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