CHLAZIDOXY Trial: Single Dose of Azithromycin verses 7-day Course of Doxycycline for Anorectal C trachomatis Infection in Women with Concurrent Vaginal Infection

Table of Content


Chlamydia trachomatis (C trachomatis) is the most commonly reported bacterial sexually transmitted infection (STI).


To compare a single dose of azithromycin with a 7-day course of doxycycline for the treatment of anorectal C trachomatis infection in women with concurrent vaginal infection

Patient Profile

Sexually active adult women (>18 years) with a positive C trachomatis vaginal swab


  • Multicentre, open label, randomised, controlled, superiority trial

In the azithromycin group, participants took four 250-mg tablets as a single dose (ie, a single 1-g dose of azithromycin), with or without food

In the doxycycline group, women were instructed to take a single 100-mg tablet in the morning and in the evening for 7 days (i.e., 100 mg of doxycycline twice per day for 7 days), at mealtimes with a glass of water and at least 1 h before bedtime

Study Outcomes

  • The primary outcome was the microbiological anorectal cure rate defined as a C trachomatis-negative nucleic acid amplification test (NAAT) result in anorectal specimens 6 weeks after treatment initiation among women who had a baseline C trachomatis-positive anorectal NAAT result
  • Secondary outcome measures were the prevalence of anorectal C trachomatis infection concurrent with urogenital infection


  • 7-day course of doxycycline was significantly more efficacious than a single 1-g dose of azithromycin for the treatment of anorectal C trachomatis infection concurrent with vaginal infection (figure1)
  • At 6 weeks, 16 women were C trachomatis-negative in the vaginal swab but C trachomatis-positive in the anorectal swab and had a visit rescheduled at 4 months.
    • Four participants from doxycycline group and 2 participants from azithromycin group cleared their anorectal infection at 4 months
Figure 1: Microbiological anorectal cure at 6 weeks by treatment group














  • Adverse events possibly related to treatment were reported in 53 (12%) of 456 women
  • Doxycycline group=24 (11%) of 228
  • Azithromycin group=29 (13%) of 228


  • The study demonstrated higher efficacy of 1-week course of doxycycline than of single dose of azithromycin for the treatment of anorectal C trachomatis infection.
  • The finding suggested that doxycycline should be the first-line therapy for C trachomatis infection in women.


Lancet Infect Dis. May 9, 2022, S1473-3099(22)00148-7