Comparing azithromycin and doxycycline for the treatment of rectal chlamydial infection: a retrospective cohort study.

Background: Centers for Disease Control and Prevention guidelines recommend azithromycin or doxycycline for treatment of rectal chlamydial infection.
Methods: We created a retrospective cohort of male patients diagnosed as having rectal chlamydia between 1993 and 2012 at a sexually transmitted disease clinic in Seattle, Washington. Men were included in the analysis if they were treated with azithromycin (1 g single dose) or doxycycline (100 mg twice a day × 7 days) within 60 days of chlamydia diagnosis and returned for repeat testing 14 to 180 days after treatment. We compared the risk of persistent/recurrent rectal chlamydial infection among recipients of the 2 drug regimens using 4 follow-up testing time intervals (14-30, 60, 90, and 180 days).
Results: Of 1835 cases of rectal chlamydia diagnosed in the study period, 1480 (81%) were treated with azithromycin or doxycycline without a second drug active against Chlamydia trachomatis. Of these, 407 (33%) of 1231 azithromycin-treated men and 95 (38%) of 249 doxycycline-treated men were retested 14 to 180 days after treatment (P = 0.12); 88 (22%) and 8 (8%), respectively, had persistent/recurrent infection (P = 0.002). Persistent/recurrent infection was higher among men treated with azithromycin compared with doxycycline at 14 to 30 days (4/53 [8%] vs. 0/20 [0%]), 14 to 60 days (23/136 [17%] vs. 0/36 [0%]), and 14 to 90 days (50/230 [22%] vs. 2/56 [4%]). In multivariate analysis, azithromycin-treated men had a significantly higher risk of persistent/recurrent infection in the 14 to 90 days (adjusted relative risk, 5.2; 95% confidence interval, 1.3-21.0) and 14 to 180 days (adjusted relative risk, 2.4; 95% confidence interval, 1.2-4.8) after treatment.
Conclusions: These data suggest that doxycycline may be more effective than azithromycin in the treatment of rectal chlamydial infections.