Doxycycline bests azithromycin in treatment of rectal chlamydia infection: NEJM

The study is published in the New England Journal of Medicine.

Rectal chlamydia is a common bacterial sexually transmissible infection among men who have sex with men. Data from randomized, controlled trials are needed to guide treatment.

Hence, Andrew Lau and colleagues from the University of Melbourne carried out the present research to compare the effectiveness of Azithromycin and Doxycycline for asymptomatic rectal chlamydia trachomatis.

In this double-blind trial conducted at five sexual health clinics in Australia, the authors randomly assigned 625 men (314 in the doxycycline group and 311 in the azithromycin group) and who had asymptomatic rectal chlamydia to receive doxycycline (100 mg twice daily for 7 days) or azithromycin (1-g single dose).

Asymptomatic chlamydia was selected as the trial focus because more than 85% of men with rectal chlamydia infection are asymptomatic, and clinical guidelines recommend a longer treatment course for symptomatic infection.

The primary outcome was a negative nucleic acid amplification test for rectal chlamydia (microbiologic cure) at 4 weeks.

The following findings were observed-

a. Primary outcome data were available for 290 men (92.4%) in the doxycycline group and 297 (95.5%) in the azithromycin group.

b. In the modified intention-to-treat population, a microbiologic cure occurred in 281 of 290 men (96.9%; 95% confidence interval [CI], 94.9 to 98.9) in the doxycycline group and in 227 of 297 (76.4%; 95% CI, 73.8 to 79.1) in the azithromycin group, for an adjusted risk difference of 19.9 percentage points (95% CI, 14.6 to 25.3; P<0.001).

c. Adverse events that included nausea, diarrhea, and vomiting were reported in 98 men (33.8%) in the doxycycline group and in 134 (45.1%) in the azithromycin group (risk difference, −11.3 percentage points; 95% CI, −19.5 to −3.2).

Therefore, the authors concluded that "a 7-day course of doxycycline was superior to single-dose azithromycin in the treatment of rectal chlamydia infection among men who have sex with men."