Doxycycline 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 1-g dose) versus doxycycline (100 mg twice daily for 7 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 and 2 weeks and 4 weeks postenrollment. The primary outcome was microbiologic cure (CT-negative NAAT) at 4 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 4-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% confidence interval [CI], 16–36%; P < .001) and the ITT population (91% [80 of 88] vs 71% [63 of 89]; absolute difference, 20%; 95% CI, 9–31%; P < .001). Conclusions A 1-week course of doxycycline was significantly more effective than a single dose of azithromycin for the treatment of rectal CT in MSM. Clinical Trials Registration NCT03608774.