you are too late as 72 hours have passed other wise you should have had PEP - post exposure prophylaxis administered these are antiretroviral drugs trying to stop sero conversion and weaken infection before its fully occured or easy to control post 72 hours after infection, these are not 100% effective but is the only available option. conclusive at 3 months test and prior to that a 4-6 week combo test ag/ab (cmia/elissa). a single incidence of penetrative sex has low infection rates world over BUT YOU ARE AT SERIUOS RISK no doubt. practice monogomy and protected if either parttner in amonogmay is infected.
If it is more than 72 hours, and somebody caught HIV, it is beyond any "anti biotic" or "injection" to eradicate the virus from the body. There is no cure known to medical science as of today for HIV.
The available treatment, called Highly Active Anti Retroviral Therapy (HAART) is a cocktail of various medicines only prescribed by experts for the patients living with HIV, after examining the progression, helps keep their viral load at minimal and CD4 counts at a reasonable level so that he can survive longer, though his post infection health condition is not as good as a normal person has. Secondly, such medication have numerous associated issues like severe side effects, risk of virus being being drug resistence, cost and life long administration.
Although HAART brought a revolutionin the treatment options of HIV and brought down the mortality rate very significantly in the developed world, unfortunately majority of the infected population living outside yet to wait many many years when such medicines will also be available to them freely.
So what is my opinion is, Prevention is the only cure as of today.
antibiotic injections? for hiv???
if you had unprotected vaginal and/or anal intercourse...you put yourself at risk for not only hiv, but other stds as well.
a test at 6-8 weeks post exposure will give you a good indication of your status...but follow it up at 3 months for a conclusive result.
was it protected or unprotected...?