The efficacy of azithromycin and doxycycline treatment for rectal chlamydial infection: a retrospective cohort study in South Australia.

Abstract

There are ongoing concerns about treatment failure with azithromycin for the treatment of rectal chlamydia. To investigate treatment efficacy of two treatments for rectal chlamydial infection. We performed a retrospective analysis of all patients diagnosed with rectal chlamydial infection between 2009 and 2015 in Adelaide, Australia. Patients were treated with either azithromycin (1 g single dose) or doxycycline (100 mg twice a day for 10 days) and returned for repeat testing 14-180 days after treatment commenced. Log-binomial models were used to estimate the relative risk (RR) of recurrent rectal chlamydia associated with the treatment with azithromycin versus doxycycline. In men, rectal chlamydia prevalence was 6.7%, and in women, it was 8.1%. Of the 526 patients diagnosed with rectal chlamydial infections, 419 (79.7%), 93 (17.7%) and 14 (2.6%) patients were treated with doxycycline, azithromycin or other medication respectively. Of these patients, 173 (41.3%) of 419 doxycycline-treated patients and 31 (33.3%) of 93 azithromycin-treated patients were retested between 14 and 180 days after treatment commenced (P = 0.16). Among these patients, the repeat rectal chlamydia test was less commonly positive in those treated with doxycycline (5.8%; 95% confidence interval (CI) 0.03-0.10) compared with those treated with azithromycin (19.4%; 95% CI 0.09-0.36) and (P = 0.01). In the multivariate analysis, azithromycin-treated patients had a significantly higher risk of a positive test in the 14 and 180 days after treatment commenced (adjusted relative risk (aRR) 2.96, 95% CI 1.16-7.57). The findings suggest that doxycycline may be more effective than azithromycin in treating rectal chlamydial infections.