I have looked through the forum and have learned a lot. I am terrified of chlamydia… I understand gonorrhea is quite symptomatic in males - and syphliss is uncommon in heterosexuals- and hiv is not transmitted through oral sex.  So that leaves chlamydia- which I also believe is uncommon in oral sex …

Here is the scenario - I was give azithromycin for sinus infection and took my last dose 10 days before I had give very brief oral sex ( less then 5 seconds and no ejaculation) to a friend- that night I popped another 500 mg of azithromycin - would my residual dose plus the 500 mg be enough antibiotic in my system to prevent infection, if my friend had chlamydia? I have no real reason to think he does- my anxiety is just getting the best of me - I have a partner and would hate myself if I gave him anything

Regarding the encounter you describe- this was very low, approaching no risk.  You are in a better positive to judge how likely it is that he might have been infected but even most people with multiple partners do not have STIs, including chlamydia.  You are correct however that if he were to have an asymptomatic infection, chlamydia is the one he would most likely have. Nonetheless, your risk of infection is still very, very low.   There would not be a meaningful residual amount of azithromycin in your system from your sinus infection to protect you from chlamydia.  Despite that, the low likelihood he was infected, the brevity of your exposure, and the fact that chlamydia is relatively poor at infecting the throat combine to make it most unlikely that you were infected.  The final dose of azithromycin you took would further reduce your risk for infection although how much is unclear.  I would not be worried in the least.  If you wish to prove to yourself that you were not infected, you could always test.  If you chose to test, I anticipate testing will show that you were not infected.  EWH

If I were in fact to have pharyngeal chlamydia would my partners penis have to come in contact with my throat to become infected? Or does it also live in the mouth/tongue/saliva ?