Question

Will PEP still work if I am not taking it strictly every 24 hours?

16 May 2022. Related: Adherence, All topics, PEP/PEPSE.

I started my 28-day PEP course 4 days ago after having oral sex with a girl and later noticed that my gum was potentially bleeding while giving the oral sex. The third day of taking PEP I was taking the pill late for 1 hour (taking it at 12:30 vs. my usual time of 11:30). The fourth day I was late for another one hour (taking it at 13:30). Today I took the pill again at 12:30 because I felt like taking it at my usual time of 11:30 would have been too soon since the last dose (13:30). Will PEP still work effectively for me? Thank you so much.

Answer

Answer: Josh Peasegood

Hi, how are you doing?

Yes PEP will still work effectively for you.

PEP needs to be taken regularly every 24 hours for it to work. But PEP does remain in the body longer than 24 hours. For this reason there is some leeway for being late or early with a dose by an hour.

Though it is best to avoid this to ensure you are maintaining a suitable level of PEP within the body. Is 11.30 still suitable for you or is it better moving your regular time to 12.30? To help remember it may be suitable to set an alarm each day to prompt you to take PEP.

Please see this link for more information about PEP:
https://i-base.info/qa/factsheets/pep-faq

Josh.

140 comments

  1. Josh Peasegood •

    Hi Thabo, how many days have you missed taking PEP all together? This does not include the days where you have taken it at a different time. Have you considered using an alarm to remind you each day of when to take PEP?

    If you have missed PEP for a couple of days, unfortunately it will reduce how effective PEP is. This is also true for taking it at different times, though to a lesser extent. How risky was your exposure? Do you know if the person was HIV positive?

    Have you had any side effects while on PEP? If you are not having a problem while on the course and you would be more comfortable, you can still continue taking PEP. There is no risk to continuing with the full course.

  2. Thabo •

    Hi Dr Please help. I started PEP on Saturday after a condom burst during sex with a stranger. I have been talking dose at 10: 00 PM. Unfortunately yesterday I forgot and went to bed, but on Tuesday I forgot to take it and went to bed but took it immediately when I woke up at 4:30 and today I unfortunately forgot too and just tool it now at 1:30 am. I am worried, should I continue and will it still work. Thank you.

  3. Josh Peasegood •

    Hi Gaga, sorry that the link did not have the information you are asking. As you started PEP within 48 hours it will be effective. PEP failure is uncommon when taken properly. In most cases PEP fails because people either do not start it soon enough or do not take it every day for the full duration of the course. When taken correctly PEP will usually work.

  4. Gaga •

    Thanks for the link josh but that doesn’t answer my question about PEP failure, is it usually works or failed idk pls help

  5. Josh Peasegood •

    Hi Gaga, please see here for more information: https://i-base.info/qa/factsheets/pep-faq

  6. Gaga •

    Hey, should i be worry about my pep? I took my first pep about 20 hours after exposure and still take it, but i have read articles about PEP failure. Im so scared.. or I shouldn’t be worried as long as I routinely take the PEP?

  7. Josh Peasegood •

    Hi Beth, as long as PEP is taken within 72 hours it can be effective. Please see here: https://i-base.info/qa/factsheets/pep-faq

  8. Beth •

    Hi

    Will Pep work effectively when taken in 53 -55 hours after the exposure.

  9. Josh Peasegood •

    Hi Mark, how long through your course of PEP are you? It sounds like you have been taking PEP for a few weeks. If this is the case there would have been a high enough amount of PEP in your body to account for being late. If this is a one-off thing it will not make a difference to how effective PEP is. In general it is best to take it at the same time each day. Is there a reason you are taking PEP between 7pm and 10pm instead of e.g., 10pm everyday?

  10. Mark •

    Hi – I am a little worried. I have been taking my PEP doses each day around 7pm-10pm. However today I fell asleep at this time and woke up at around 4am (essentially 9 hours later than the usual time frame – 36 hours since the last dose) and quickly took the PEP then. Will I be OK? Will the PEP now be less effective or will it make no difference?