Q and A

Question

Do I need PEP if I only took on-demand PrEP an hour before?

Hi, I have been on daily prep for HIV for 4 years. Due to covid-19 I was stopped taking my prep for 3 weeks. Yesterday I was visited by a girlfriend around 20:00 hrs so I took 2 tablets of lamivudine/tenofovir around 21:00 hrs we started kissing and we ended up having unprotected sex. Am worried since I did not wait for 2hrs to 24hrs before sex. Am I going to be ok or I should sex for PEP? Please help since am running of time for PEP.

Answer

Hi there

Don’t worry about not quite being two hours. At least one of the drugs (emtricitabine) is already active within 30 minutes and the other takes much longer so an hour either way will be okay.

Please make sure you take another single pill 24 hours after the first dose, and another one 24 hours after this.

Using PrEP like this is called on demand dosing.

See here for more info: Taking PrEP on demand and: Real life examples of PrEP on demand dosing.

4 comments

  1. Josh Peasegood

    Hi Karan, what you have described is a very low risk exposure. Having only a single brief insertion before using a condom means the time for transmission is very limited.

    While you have taken some PrEP, you have not taken PrEP most effectively. Using on-demand dosing should be 2 pills 2-24 hours before sex, and then PrEP the following 2 days at the same time you had taken the double dose.

    Having taken some PrEP in the days prior and taking some before and after will provide some protection reducing the risk further. The symptoms you have described are not suggestive of HIV seroconversion and you do not need to remain on PrEP for this time (unless still using it for other events). As you have mentioned, the most likely cause of your symptoms is the anxiety and stress you are feeling around this event.

    More information about transmission can be found here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing

  2. Karan

    Hi Simon,

    On a Saturday, I took one prep pill 30 min before and one immediately after the hookup. We had a brief single insertion of unprotective anal sex, and the rest was with condoms. I have been taking PrEP since then daily (17 days). I also took 2 pills the Monday before and one each on the Tuesday and Wednesday before, but none on Thursday and Friday leading up to the Saturday. I have been experiencing symptoms of dull periodic headache, dizziness, head pressure, and a lot of stress and anxiety from thinking about this event. Symptoms have lasted since that Saturday and began almost the same day or next day.

  3. Josh Peasegood

    Hi Arthur, does this mean Thursday was the only day you did not take PrEP?

    If this is the case re-starting on-demand PrEP PrEP on the Friday will be okay and it matters less that you started less than 2 hours before sex.

    Your previous course of on-demand PrEP will still have some effect and will allow for protecting you. You are safe.

  4. Arthur

    I had sex last on Monday but ended up taking the last two dosage and ended on Wednesday then i had unprotected sex again on Friday but this time I took prep 30mins-1hr before sex …I’m I safe ?

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