Doxycycline better than azithromycin for treating Chlamydia trachomatis infection in MSM

Chlamydia trachomatis infection is the most commonly reported sexually transmitted infection (STI) in the United States, with approximately 2.8 million infections reported annually.

A new study by Dr Mary B. Keegan, MD and team reported that Azithromycin and doxycycline are both recommended treatments for rectal Chlamydia trachomatis (CT) infection however doxycycline was significantly more effective than a single dose of azithromycin for the treatment of rectal CT in men who have sex with men (MSM).

This study is published in Clinical Infectious Diseases.

The objective of the study was to determine whether Azithromycin and doxycycline, which is a better drug to treat Chlamydia trachomatis infection.

The study was a randomized, double-blinded, placebo-controlled trial compared azithromycin (single 1-g dose) versus doxycycline (100 mg twice daily for 7 days) for the treatment of rectal CT in men who have sex with men (MSM) in Seattle and Boston. Participants were enrolled after a diagnosis of rectal CT in clinical care and underwent repeated collection of rectal swabs for nucleic acid amplification testing (NAAT) at study enrollment and 2 weeks and 4 weeks post enrollment. The primary outcome was microbiologic cure (CT-negative NAAT) at 4 weeks. The complete case (CC) population included participants with a CT-positive NAAT at enrollment and a follow-up NAAT result; the intention-to-treat (ITT) population included all randomized participants.

The results of the study were found to be

• A total of 177 participants were enrolled in the study, 135 (76%) met CC population criteria for the 4-week follow-up visit. Thirty-three participants (19%) were excluded because the CT NAAT repeated at enrollment was negative.

• Microbiologic cure was found to be higher with doxycycline than azithromycin in both the CC population (100% [70 of 70] vs 74% [48 of 65]; absolute difference, 26%; 95% confidence interval [CI], 16–36%; P < .001)

• The ITT population (91% [80 of 88] vs 71% [63 of 89]; absolute difference, 20%; 95% CI, 9–31%; P < .001).

Dr. Keegan and team concluded that "A 1-week course of doxycycline was significantly more effective than a single dose of azithromycin for the treatment of rectal CT in MSM."

For further information: https://academic.oup.com/cid/article-abstract/73/5/824/6144986