less than 24 hours ago I was the receptive partner in anal intercourse. the condom broke and partner withdrew. He did not ejaculate but it is highly likely that precum was present, the ER doc has prescribed 150mg/twice daily combovir for 28 days. In the best case scenario that my partner is negative - am I doing myself any harm? Elevating my risk in anyway for future exposure? Thank you very much for your input.
Taking PEP (post-exposure prophylaxis) does not elevate your risk in any way for acquiring HIV in the future. The only risk associated with PEP involves side effects/toxicities of the medications. For instance, the AZT component of your Combivir can cause anemia in some folks.
If you are still in contact with your top gun, why not ask him to get a rapid HIV test. If he's negative, your chance of contracting HIV would be limited to the remote possibility that he was in his window period. You can read much more about PEP in the archives. Have a look!