Treatment Effectiveness of Azithromycin and Doxycycline in Uncomplicated Rectal and Vaginal Chlamydia trachomatis Infections in Women: A Multicenter Observational Study (FemCure)

Rectal infections with Chlamydia trachomatis (CT) are prevalent in women visiting a sexually transmitted infection (STI) outpatient clinic, but it remains unclear what the most effective treatment is. We assessed the effectiveness of doxycycline and azithromycin for the treatment of rectal and vaginal chlamydia in women. This study is part of a prospective multicentre cohort study (FemCure). Treatment consisted of doxycycline (100 mg twice daily for 7 days) in rectal CT positive women, and of azithromycin (1 g single dose) in vaginal positive women who were rectally untested or rectally negative. Participants self-collected rectal and vaginal samples at enrolment (treatment timepoint) and during 4 weeks of follow-up. The endpoint was microbiological cure by a negative nucleic acid amplification test at 4 weeks. Differences between cure proportions and 95% confidence intervals (CIs) were calculated. We analysed 416 patients of whom 319 had both rectal and vaginal chlamydia at enrolment, 22 had rectal chlamydia only, and 75 had vaginal chlamydia only. In 341 rectal infections, microbiological cure in azithromycin treated women was 78.5% (95%CI: 72.6 to 83.7, n=164/209) and 95.5% (95%CI: 91.0 to 98.2, n=126/132) in doxycycline treated women (difference 17.0%, 95%CI: 9.6 to 24.7, p<0.001). In 394 vaginal infections, cure was 93.5% (95%CI: 90.1 to 96.1,n=246/263) in azithromycin treated women and 95.4% (95%CI: 90.9 to 98.2,n=125/131) in doxycycline treated women (difference 1.9%, 95%CI: -3.6 to 6.7,p=0.504). The effectiveness of doxycycline is high and exceeds that of azithromycin for the treatment of rectal CT infections in women.