[Question #8953] PREP, Anal STI

37 months ago

Hi doctors,

After my encounter last fall and having to take PEP, I got onto PREP to be as safe as possible. I have been on PrEP for 4 months now and all tests had been good. The big however. Last Thursday, I was with someone where I was the receptive bottom. They did not cum inside me but I had rectal sti symptoms - discharge and constipation. I went to the doctor who treated me with a shot and 7 days doxy. My questions are as follows:

1. Does this put me at greater risk of HIV since I got an STI. I am religious about taking PREP every day and never missed a dose. Or does prep protect me the same regardless?

2. If I took an HIV 4th gen test at 4 weeks after incident, would this be indicative of my status? Even though I am on Prep? Or would I need a viral load test?

3. This whole incident really kind of freaked me out. If I decide to abstain from anal sex, I would quit taking prep. How long do I need to continue taking prep after last incident to stay protected. I see some websites say 7 days, some say 28 days and others say 2 days for the on demonic prep.

Thank you very much in advance for your answers.

Edward W. Hook M.D.

37 months ago

Welcome to our forum. Thanks for your confidence in our service. Congratulations as well on your decision to regularly take PrEP. This will do an outstanding job of reducing your risk for acquisition of HIV to close to zero. STI‘s, including rectal infections, are common in persons who are taking PrEP. While data are limited,,I would not be concerned that your recent symptoms would particularly increase your risk for acquisition of HIV. Admittedly, failures in person to take prep as directed are so rare that is there are few data on precisely what factors do lead to failure of this important therapy. Reply to your specific questions:

1. Please see my comments above. There are no data to suggest that your recent symptoms and possible acquisition of another infection would reduce the efficacy of your PrEP.

2. As mentioned above, failures of prep when taken properly as you have are quite rare and so there are few data detection of treatment failures. If you had acquired HIV is the result of your recent encounter, I would anticipate that a fourth generation, combination HIV antigen/antibody test would effectively detect that by six weeks and most probably by four weeks after the encounter. I see no reason to pursue the time and expense of an HIV viral load (PCR).

3. Estimates on how long one should take PrEP following an exposure are variable because there are so few data. As you point out, for persons taking PrEP on demand, medications are present in the system for only two or three days. Should you make a decision to discontinue PrEP, I would anticipate that it would be entirely effective as long as you waited at least seven days to discontinue the medication.

I hope my comments above are helpful. I am confident that your PrEP protected you and you should not let recent events concern. Should there be additional questions or if any part of my replies unclear, please use your up to follow ups for clarification. Take care. EWH

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37 months ago

Hi doctor - I really appreciate your response and provides quite a bit of reassurance. I have read much on the internet about prep effectiveness and I see people put it between 86% and nearly zero. From detail on case studies it seems like closer to zero based on case studies since almost 1m people on prep and they have had less than 10 failures. Seems much higher than 86%. When I was put on prep, they tested me the day they provided Truvada, 30 days later and 3 months later so I can rule out previous infection. Last couple questions and I think we can close the thread.

1. If I wanted to take an hiv rna test for piece of mind, would 11.5 days be enough? A testing site here offers hiv rna per testing. I would imagine there would be enough virus after 10 days to rule it out if test is negative.

2. As for syphillis, I read that would be a 14 day treatment of doxycycline. I took for 7 days but within 3,5 days after encounter. Would that be sufficient to ward of syphillis if take so soon? Or should I take another 7 days to be sure?

3. If for some reason I did contract syphillis anally, could I pass it on through my penis or is it localized to anus?

Thank you

Edward W. Hook M.D.

37 months ago

welcome back to the Forum. Let me start by urging you to avoid the internet - much of what is found there is misleading, either because it is out of date, taken out of context, or because it is just plain wrong. PrEP for HIV prevention is VERY, VERY effective in preventing acquisition of HIV with effectiveness in persons who take their medication regularly as you have been are close to 100% protected from infection. Between the fact that most exposures to untreated, infected partners do not result in infection (less than 1% of exposures result in infection), the fact that you do not know that your partner had HIV, and the high efficacy of PrEP, your chance of being infected is vanishingly low. In response to your follow-up questions:

1. As I said above, failures of PrEP are so rare that there are no good data on when failures test positive. An HIV RNA PCR would turn positive a few days before a routine 4th generation HIV test. Obviously, any negative test would be reassuring if yo feel the need although I am confident that you were not infected through the exposure you described above.

2. Treatment for recently acquired syphilis would require 14 days of doxycycline however prevention following recent exposure can be accomplished with less medication. IF you were exposed to syphilis in your exposure of concern, 7 days of doxycycline would prevent infection. No need for more.

3. If you were to acquire syphilis anally, the lesion of infection would be in the ano-rectal region, not on the penis.

I hope this information is helpful. I am confident you are not at meaningful risk for HIV or further STIs from the encounter you described. Please stay off the internet. EWH

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