DoDoxycycline Versus Azithromycin for the Treatment of Rectal Chlamydia in Men who have Sex with Men: A Randomized Controlled Trial.

BACKGROUND: Azithromycin and doxycycline are both recommended treatments for rectal Chlamydia trachomatis (CT) infection, but observational studies suggest that doxycycline may be more effective.

METHODS: This randomized, double-blind, placebo-controlled trial compared azithromycin (single one-gram dose) vs. doxycycline (100mg twice daily for seven days) for the treatment of rectal CT in men who have sex with men (MSM) in Seattle and Boston. Participants were enrolled after a diagnosis of rectal CT in clinical care and underwent repeated collection of rectal swabs for nucleic acid amplification testing (NAAT) at study enrollment, two weeks, and four weeks post-enrollment. The primary outcome was microbiologic cure (CT-negative NAAT) at four weeks. The complete case (CC) population included participants with a CT-positive NAAT at enrollment and a follow-up NAAT result; the intention-to-treat (ITT) population included all randomized participants.

RESULTS: Among 177 participants enrolled, 135 (76%) met CC population criteria for the four-week follow-up visit. Thirty-three participants (19%) were excluded because the CT NAAT repeated at enrollment was negative. Microbiologic cure was higher with doxycycline than azithromycin in both the CC population [100% (70 of 70) vs. 74% (48 of 65); absolute difference 26% (95% CI: 16-36%; p<0.001)] and the ITT population [91% (80 of 88) vs. 71% (63 of 89); absolute difference 20% (95% CI: 9-31%; p<0.001)].

CONCLUSIONS: A one-week course of doxycycline was significantly more effective than a single dose of azithromycin for the treatment of rectal CT in MSM. (Funded by National Institute of Allergy & Infectious Diseases contract HHSN272201300014I, Protocol 17-0092).