Randomized, open-label, multicenter study of azithromycin compared with doxycycline for treating anorectal Chlamydia trachomatis infection concomitant to a vaginal infection (CHLAZIDOXY study)

Background: Chlamydia trachomatis can lead to a persistent infection in the lower gastrointestinal tract, suggesting a potential role of autoinoculation of cervical chlamydial infection from the rectal site, contributing to repeat infections. Moreover, around 75% of women with urogenital C. trachomatis have concurrent anorectal infection. Current treatment guidelines for urogenital C. trachomatis infection recommend either a single 1 g dose of azithromycin or doxycycline 100 mg twice daily for 7 days. Doxycycline appears to be more effective in treating anorectal infections as suggested in a population of men who have sex with men, but no randomized controlled trial (RCT) had directly compared azithromycin with doxycycline for the treatment of rectal infections. We propose an open-label RCT to compare the microbial cure obtained with a single 1 g dose of azithromycin versus 100 mg of doxycycline twice daily for 7 days, for the treatment of anorectal C. trachomatis infection concurrent to urogenital infection in women. Methods and study design: A total of 460 women with C. trachomatis urogenital infection will be enrolled in the study. Women will be asked to provide self-collected anorectal swabs and will be randomized to receive either a 1 g single dose of azithromycin or doxycycline 100 mg twice daily for 7 days. Clinical and biological data will be collected and patients will complete questionnaires about their sexual behavior. The primary outcome is the microbial cure rate, defined as a C. trachomatis negative nucleic acid amplification test (NAAT) result in the anorectal specimens 6 weeks after treatment initiation among women with a C. trachomatis positive urogenital and anorectal NAAT result at the baseline. The secondary outcome is autoinoculation from the rectum to the vagina, which will be evaluated based on the number of women with the same C. trachomatis genotype profile that will be identified in an anorectal-positive specimen obtained 6 weeks after treatment initiation and in a vaginal-positive specimen obtained four months after treatment. Discussion: The results of this trial will establish which treatment is more efficacious against anorectal infection and could affect recommendations for the treatment of urogenital C. trachomatis infection, taking into account concurrent anorectal infection. ClinicalTrials.gov Identifier: NCT03532464. Date of registration: May 31, 2018.