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

Intern Med J. 2018 Mar;48(3):259-264. doi: 10.1111/imj.13624.


Background: There are ongoing concerns about treatment failure with azithromycin for the treatment of rectal chlamydia.

Aim: To investigate treatment efficacy of two treatments for rectal chlamydial infection.

Methods: 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.

Results: 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).

Conclusion: The findings suggest that doxycycline may be more effective than azithromycin in treating rectal chlamydial infections.

Keywords: Chlamydia trachomatis; azithromycin; doxycycline; rectal; treatment.

MeSH terms

  • Adult
  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use*
  • Azithromycin / pharmacology
  • Azithromycin / therapeutic use*
  • Chlamydia Infections / diagnosis
  • Chlamydia Infections / drug therapy*
  • Chlamydia Infections / epidemiology*
  • Cohort Studies
  • Doxycycline / pharmacology
  • Doxycycline / therapeutic use*
  • Female
  • Humans
  • Male
  • Rectum / microbiology
  • Retrospective Studies
  • Sexual Behavior / drug effects*
  • South Australia / epidemiology
  • Treatment Outcome
  • Young Adult


  • Anti-Bacterial Agents
  • Azithromycin
  • Doxycycline