Q and A


Does PrEP work for active partner and for oral sex?

Hi, I read your article on PrEP with great interest. I note that you only make reference to the protection offered to the receiving partner in anal and vaginal sex. It appears to me that this leaves out th einsertive partner, and all people engaging in oral sex.

Are you able to state what is the relative level of deposition of these drugs in the tissues of the mouth, glans and inside foreskin compared to the tissues of the anus and vagina, the timescale for safe deposition and the corresponding  protection offered?

Basically, what are the effects of PrEP if you are the exclusively giving partner of anal or vaginal sex or recipient of oral sex, or exclusively a giver of oral sex?

Many thanks.



This is an interesting aspect of PrEP which is rarely emphasied – especially protection from oral sex if you are giving oral sex on a man.

Although there is no direct data on this that I am aware of, PrEP is likely to work for any type of sexual activity, because oral drugs are absorbed into the blood which travels around your whole body. This means it would reach lymph nodes throughout the body, including clsoe to the mouth, and one of the places that PrEP is thought to work is in lymph glands.

PrEP studies have reported absorption into vaginal and rectal tissue because being the receptive partner generally has a higher risk than for a man who is insertive. It is also because durg absorption into these two key tissues are know to be different and this affects different levels of adherence needed for similar protection.

It is reasonable I think to assume that PrEP is just as effective for oral sex and for a man who is having insertive sex. This is because people are likely to have taken different roles during the PrEP studies and also would have had oral sex.

If PrEP is close to 100% effective when taken as prescribed for highest risk risk sex it will be just as effective for rsiks that are much lower.

I haven’t seen any data about drug levels in other tissue sites – even from animal studies – but the level of protection is likely to be at least as good, and similar dosing advice seems reasonable.

Also, researches are still not certain of exactly how PrEP works – and which are the target levels even in anal and rectal tissue compartments.

This new i-Base guide hase more detials about dosing options.


  1. Simon Collins

    Hi Susan – great you are now on treatment. This should make your viral load undetectable and help your CD4 count increase. If you partner has tested negative all thistime, then it is likely that he is negative. It is common for only one partner to test positive even if you are not alwasy using condoms. For the future, once your viral load is undetectable, the risk to your partner will be dramatically reduced. This means you could continue having sex without condoms if this is your preference

  2. Susan

    I started taking Tribuss from 30th May 2016 with a CD4 count of 160 I would like to find out, if its possible that my partner has been testing nagetive all these years and not positive ,is there a possibility that he might also have the the virus if we continue having unprotected sex? or is there a possibility that I might increase my viral load and lower my cd4 count.