Question
Is PEP effective if taken 48 hours after exposure?
2 July 2021. Related: All topics, PEP/PEPSE.
I paid for sex with a woman but the condom tore and I only realised after I was done. There is a high chance that she was HIV positive. I started PEP after 48 hours.
I got a PCR test done 17 days after exposure. It had a less than 20/ml (undetectable) result.
Now between 14 and 35 days after exposure I have had signs of thrush, mild red rash on my face and a couple elsewhere. But no fever or swollen lymph glands.
Can the rash and thrush be because of utter stress and obsession?
My doctor says that the PCR can be relied upon and that I am negative.
Can the PEP have reduced the viral load to less than 20/ml as I took it for 15 days before the PCR test?
Please give your expert advice. I am very anxious. Thank you.
Answer
Thank you for your question.
The risk of HIV from one broken condom is very low. If your partner had an undetectable viral load on treatment, then the risk would be zero. If they were not on treatment the risk might still be only 1 in 300 or lower.
You cannot guess someones HIV status so your assumptions might also be wrong.
You started PEP within 48 hours, so it is likely it will work.
PEP – stands for Post-Exposure Prophylaxis. It is a term used for taking HIV drugs to reduce the risk of infection. PEP usually involves taking a combination of three HIV drugs for one month. The earlier PEP is started, the more likely it will work. Ideally, this should be within a couple of hours. If this is not possible, then still the earlier the better.
Some guidelines include a two-day window to do this (i.e. within 48 hours). After this, effectiveness is much less likely. Other guidelines allow up to 3 days (i.e. within 72 hours). Sometimes this may be more for psychological benefit. For example, if someone is very stressed or traumatised.
No guidelines recommend starting PEP after 72 hours.
After finishing PEP you need to wait a 4-6 weeks before testing.
If the PEP has worked, or the person was not initially infected, this will show as a negative HIV test. The test you did 17 days after the exposure will not be accurate yet.
If the PEP has not worked, this will be shown in a positive test result. Testing 4 weeks after PEP will detect 95% of infections. Testing after six weeks will detect more than 99% of infections. This result doesn’t need to be tested again.
If PEP has not worked, serosonversion usually occurs 1-3 weeks after PEP is finished. However, only 80% of people show symptoms.
Please test 6 weeks after you finished PEP is finished. If you test any earlier, you need to take a second test 3 months later.
Viral load (PRC) tests are not approved to test for HIV. In some cases they can have a role.
Please see a doctor to talk about your symptoms he best way to confirm what is causing them is to see your doctor. He/she will be able to diagnose and treat the symptoms accordingly.
Note: This answer was last updated in July 2021 from an original post from December 2011.
Hi ygo, being late on one occasion is not going to risk PrEP not working. You are still safe.
hello good day doctors i have been taking prep and i took it twice at 11:30 pm because i normally take it around 9pm or 10pm before i go to bed and i missed a pill am i still safe
Hi Maddi, your result is conclusive. You do not have HIV and you are not required to take any further tests.
Hi I tested 43 days after my last dose of PEP and 73 days after possible exposure using a 4th generation ab/ag with reflux is this test accurate if it’s negative or do I need another test?
Hi Daniela, please follow this link to our PEP F&Q: https://i-base.info/qa/factsheets/pep-faq
I started pep with in 44hours now after finishing pep I tested my self and I was negative but am scared and all day crying I feel like killing my self cause I don’t know what to do. But I pray to come out negative
Hi Twijukye, as you had used it the first time with no problems it is likely that this rash has not been caused by PEP. Have you gone to see a doctor about your rash?
I used PEP for the first time and I didn’t have any problem. But when I used it for the second time, I used for the second time, I experienced rashes after 3 weeks. What could be the cause?
Thank you Richard for pointing this out, the original post has been amended.
The answer is wrong, it says: “Other guidelines allow up to 4 days (i.e. within 72 hours). Sometimes this may be more for psychological benefit.” … 72 hours is 3 days not 4!