Question
Late with the after sex on-demand PrEP dose.
5 March 2022. Related: Adherence, All topics, PrEP.
Hello for all. I started 2-1-1 prep, took 2 pills 3 hours before sex. Then I took second pill after 24 hours after sex, not 24 hours after the first 2 pills – I have delayed the second pill by 3 hours. I’m still continuing taking PrEP every day because I have sex but I am just worrying is it ok to delay the second dose by 3 hours? Thank you for reply.
Answer
Hi, how are you doing?
Being 3 hours late on the second dose is not likely to cause a problem. The initial double dose will have increased the drug levels within your body more than a single dose anyway. These drugs tend to remain at the required drug level within the body for more than 24 hours.
While it is best to take the medication as routinely as you can, being late by 3 hours is unlikely to cause you any problem. As you have now continued with daily dosing, PrEP will have remained at effective level within your body.
There is no reason to be concerned after this event,
Josh.
Hi Robert, this i-Base service isn’t set up as either an emergency service, or run by people who can prescribe PrEP. However, the double dose when starting PrEP generally gives very high levels of protection though that cover the following doses being a bit late.
You are not describing a high level of risk.
Please realise that there is no data on the impact of slightly late or early doses because even in research studies this level of detail for events that happened months earlier is never available.
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Hi Josh,
I’m a 38-year-old cisgender man using on-demand PrEP (TDF/FTC, Truvada equivalent). I’m seeking urgent advice because I had a potential HIV exposure this weekend and need to determine whether PEP is necessary before the 72-hour window expires.
Here is my exact timeline:
Saturday, 10 October, 5:30 PM: Took the initial double dose (2 tablets) of PrEP.
Saturday, approximately 10 PM–midnight: Had receptive anal sex without a condom with a partner whose HIV status is unknown. There was no ejaculation. A shared dildo was also used.
Sunday, 11 October, 7–11 AM: Had oral sex without ejaculation and condom-protected anal sex.
Sunday, approximately 1 PM: I may have taken one PrEP tablet, but I’m not certain, so I’d prefer to assume I missed this dose.
Sunday, 11:30 PM: Definitely took two PrEP tablets together, approximately 30 hours after the initial double dose.
Monday, 12 October: Planning to continue PrEP, but need advice on the correct timing and number of remaining doses.
I’ve read the HIV i-Base guidance explaining that delayed event-based PrEP doses may still maintain protective drug levels, particularly when the initial double dose was taken correctly.
My questions are:
Given that I correctly took the initial double dose 4.5–6.5 hours before receptive anal sex, and subsequently took two tablets approximately 30 hours later, would I still be considered adequately protected against HIV?
Does this dosing history warrant starting PEP, or can I safely continue PrEP without PEP?
What is the appropriate timing and duration of my remaining PrEP doses?
This is time-sensitive: The 72-hour window following Saturday’s exposure closes on Tuesday, 13 October, approximately 10 PM–midnight (Mexico time). I would be extremely grateful for your advice as soon as possible.
Thank you very much for your help.