[Question #9847] Azithromycin dosing

28 months ago

I recently found this site, and am amazed at the service you provide!

I may or may not have an unrealistic fear of STDs… anywho to the question..

If I was “exposed” to chlamydia via oral sex and took 1g of azithromycin 1 week after exposure, proceeded to vomit about an hour later, then took an additional 500mg over 6 hours. Would that be enough medication in my system to cure said exposure? A week after the azithromycin, I had a chlamydia NAA done and it was negative, could that be because I truly did not have chlamydia at the time or was it a false negative with the not correct dose of azithromycin delaying enough bacterial growth to make it positive?

28 months ago

* incorrect dose delaying a true positive

H. Hunter Handsfield, MD

28 months ago

Welcome back. I'm sorry you didn't think of this question during your recent discussion with Dr. Hook; he could have answered it quickly and succinctly.

You really weren't at risk for chlamydia. In contrast to what you can find online, oral to penile transmission of chlamydia is very rare. Oral chlamydia can occur but is uncommon; and when present, almost always is in very low numbers of organisms that are rapidly cleared by the immune system. Therefore, oral sex rarely even exposes someone to chlamydia, and actual transmission therefore is very rare.

That said, if in fact you were exposed, the azithromycin you took was 100% effective in preventing actual infection. In the early days of experience and research with azithromycin, it was established that vomiting more than 30 minutes after ingestion does not reduce effectiveness against chlamydia; enough has been absorbed that that time to do the job. And your second dose of 500 mg provided further assurance.

You can be completely certain you do not have chlamydia at this time. (You don't mention gonorrhea or other STDs, which are higher risk than chlamydia from oral sex. However, the azithromycin also would have been good protection against them, and absence of symptoms by this time is nearly 100% proof you didn't acquire gonorrhea.)

So all is well. I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

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28 months ago

Thanks for the quick reply. I am sure you understood, but I just wanted to clarify, I took the azithromycin 1 week after possible exposure.

Also, could you briefly explain NAA testing, I understand that it looks for DNA. In the off chance I had acquired chlamydia ( I know, very rare and unlikely) could my negative NAA be false due to incorrect azithromycin or was the fact that my NAA was negative meant I was no longer infected?

Lastly, I’m sorry for the questions, but how long can a male stay asymptomatic from chlamydia?

H. Hunter Handsfield, MD

28 months ago

Happy to clarify this. Indeed, I did not realize that you took the azithromycin a week after the sexual exposure. However, it makes no difference. Azithromycin in the dose(s) you took is nearly 100% effective against urethral chlamydia. As for your question about NAAT, indeed it detects nucleic acid (for chlamydia, it detects RNA not DNA), and it is not possible to have chlamydia present without detectable RNA. In fact, after treatment it's exactly the opposite situation: RNA can persist days or even a couple of weeks after chlamydia has been killed. And as I said, you had a zero risk exposure for chlamydia: had you asked me after the exposure, I would have advised against both testing and treatment as unnecessary. As discussed above, you were a far higher risk for gonorrhea. But you can be completely certain you did not acquire chlamydia and do not have it now.

Asymptomatic chlamydia can persist for weeks or even a few months. But this is now irrelevant. Why are you so concerned about chlamydia in particular? As opposed to more frequent and/or more dangerous STDs like gonorrhea and syphilis?

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28 months ago

Thank you for your reply. I know that my risk was very low and close to zero, but I have OCD and I tend to fixate on things, chlamydia for example. I know that 90% of men are symptomatic when it comes to gonorrhea, syphilis is rare in heterosexuals ( I have read that many times in your site) and HIV is also rare transmitted orally. I even know that chlamydia is even rare in the oral cavity, but I guess I get nervous when it comes to chlamydia due to the long asymptomatic period

H. Hunter Handsfield, MD

28 months ago

All correct, although more like 99% of urethral gonorrhea cause obvious symptoms. That's because it is virulent and can be seriously damaging, sometimes very soon after infection. It's really not rational to be more fearful of chlamydia because it often is asymptomatic; I would advise the oppose attitude. (Recognizing, of course, that almost by definition, obsessions rarely respond to facts and reason alone!)

As that implies, we're very aware and sensitive to OCD on this forum, and I'm not surprised by your acknowledgement of it. But do be aware that repeated anxiety driven questions -- even if not exactly on the same topic (different STDs, for example) are discouraged. Of course don't hesitate to return if something entirely new is of concern to you.

That concludes this thread. Best wishes and stay safe.

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