[Question #349] Question regarding the treatment of Chlamydia

95 months ago

So my name is Joe and I am in my last year of Pharmacy School, currently doing a rotation in a underserved clinic. I received a question from a patient, which I am now doing a care plan on, but have run into a lack of information, which is why I figured I would post here as Dr. Handsfield and Dr. Hook are the best in the field. 

So the patient presented to the clinic with a few concerns, but the major one being that a recent partner of hers told her he was recently diagnosed with Chlamydia. However the patient was treated a week ago with a Z-pak for a sinus infection (500mg day 1, followed by 250mg days 2-5). The patient stated she had recently received STD testing and was clean, but still was a bit nervous. The patient asked if the Z-pak would have cleared the chlamydia infection. So my preceptor had me do a write up on this topic.

While we know that the traditional dose of azithromycin to treat chlamydia is a one time 1 gram dose, i believe a Z-pak would still be effective. Due to Azithromycin's long half life of 68 hours (but quick absorbing of about 2 hours), technically a patient would receive 1gram once taking the day 3 dose, and would still have another two days of therapy. 

As far as studies go, the only study I could find that includes multi-day treatment with azithromycin for chlamydia is below. However it did support my hypothesis that a multi day azithromycin treatment would clear Chlamydia (and they only did three days of therapy)  and actually mentioned that it had the highest clearance rate of Chlamydia. The study is below: 


So would you agree that a 5-day z-pak treatment would be effective in treating a Chlamydia infection? If so, is it just not preferred compared to the one time 1 gram dose due to the possibility of adherence issues?

I appreciate your time and input, as well as all you have done in this field!


H. Hunter Handsfield, MD
95 months ago
Welcome to the forum and thank you for an interesting question.

As you correctly discerned, most STD experts would agree that azithromycin in Z-Pak type regimens would be fully effective against uncomplicated chlamydial infection. But as you also found, there are few studies. I probably read the study you cite but didn't remember it, published almost 25 years ago. But I'm not surprised by it, and I agree it provides support for the efficacy of such regimens. You may be able to find others if you keep digging. (At one time I was friends with the senior author, Geoff Ridgway. He's now retired and we haven't been in touch recently.) However, it can't be considered definitive. It was a rather small study, and back in those days only culture was available to detect C. trachomatis; we now know that nucleic acid amplificaiton tests (NAATs) are more sensitive and sometimes detect treatment failures missed by culture. We also know now that some treatment failures aren't detected until 6-12 weeks after treatment, but most early studies followed patients for only 2-4 weeks. I can't pull up the full article from that far back, and the abstract doesn't state the follow-up time, but I would be surprised if they went beyond 3-4 weeks.

Single dose treatment, ideally directly observed by the treating physician or clinic (or a pharmacist), is generally preferred for STD treatment. As you suggest, it assures compliance, in a setting in which many persons might be inclined to share treatment with their sex partner(s), leading to undertreatment of both.

So I always use and recommend azithromycin1.0 g single dose, but I'm quite confident that 3-5 day regimens usually would be effective. If someone has been so treated, I do not recommend routine re-treatment, but I strongly advise follow-up testing in a few weeks to assure cure (and to exclude reinfection, which is common). In addition, there is growing concern that although treatment failures with azithromycin are uncommon, they may be more frequent than with doxycycline, especially for non-genital (rectal, pharyngeal) infection. I wrote an editorial about this a few years ago, since which time more studies have continued to raise doubts. But I would emphasize retesting even more strongly for someone treated with a non-standard azithro regimen.

Thanks again for your question. Let me know if anything isn't clear--


95 months ago
Yea that all makes sense. Also I pulled up the article and it was a 3-4 week follow-up. Out of curiosity, why would it take so long (6-10 weeks) for treatment failure to appear? Just the regeneration of the bacteria in the active site? I only ask because if I am not mistaken, a active infection would be seen 3-4 weeks after exposure?

Also, the physician did like you had mentioned, re-test in 4-weeks and said even if she was exposed, the z-pak would have eradicated the infection.

I will keep digging for more articles, but overall, for uncomplicated chlamydia, you would agree that 5-day therapy would be effective?

Once again, thank you for the information!!
H. Hunter Handsfield, MD
95 months ago
Chlamydia is slow growing anyway, and regeneration might take longer in a patient who has been infected for a while with an immune response to it -- which isn't typically an issue when someone is newly exposed. But that's mere speculation; a chlamydia biologist might know more about this, but that's as far as my expertise goes. Also, the research on persistence with azithromycin has also shown that a GI tract reservoir may contribute; in animal models, azithro doesn't work well against chlamydia in the GI tract, which might then serve as a reservoir to reinoculate the genital tract.

I already said that I believe a 5 day course would be effective, but I don't see that it matters much. For teh reasons above, it would not and should not be recommended in clinical practice.