NEW YORK (Reuters) – A one-week course of doxycycline was superior to a single dose of azithromycin in women with concurrent vaginal and anorectal chlamydia infection in an unblinded randomized controlled trial, mirroring previous results in men.

Researchers suggest that doxycycline should be the first-line therapy for chlamydia infection in women.

“It is clear we must consider that any woman with a urogenital infection must have an effective treatment for the anal infection, since nearly 80% of women have an anal infection concomitant with the vaginal infection,” Dr. Bertille de Barbeyrac of the University of Bordeaux, France, told Reuters Health by email.

However, she noted that “even [though] the study shows that doxycycline is more effective than azithromycin on anal infection, other studies are needed to prove that residual anal infection after treatment with azithromycin can be a source of vaginal contamination and therefore justify changing practices and eliminating azithromycin as a treatment for lower urogenital chlamydial infection in women.”

“There are other reasons [to make] this change,” she added, “such as the acquisition of macrolide resistance by M. genitalium following heavy use of azithromycin.”

As reported in The Lancet Infectious Diseases, Dr. Barbeyrac and colleagues randomly assigned 460 women (median age, 21) to either doxycycline or azithromycin in a multicenter, open-label superiority trial.

Participants received either azithromycin (a single 1-g dose, with or without food) or doxycycline (100 mg in the morning and evening at mealtimes for 7 days – that is, 100 mg of doxycycline twice daily).

The primary outcome was that the microbiological anorectal cure rate, defined as a C. trachomatis-negative nucleic acid amplification test (NAAT), resulted in anorectal specimens six weeks after treatment initiation among women who had a baseline positive result (about half the women in each treatment group).

Ninety-four percent of the doxycycline group versus 85% of the azithromycin group had an anorectal cure (adjusted odds ratio with imputation of missing values, 0.43).

Adverse events possibly related to treatment occurred in 11% of the doxycycline group versus 13% of the azithromycin group. Gastrointestinal disorders were most frequent, occurring in 8% of the doxycycline and 11% of the azithromycin groups.

Summing up, the authors write, “The microbiological anorectal cure rate was significantly lower among women who received a single dose of azithromycin than among those who received a 1-week course of doxycycline. This finding suggests that doxycycline should be the first-line therapy for C trachomatis infection in women.”

Dr. Meleen Chuang, medical director of women’s health at the Family Health Centers at NYU Langone, Brooklyn, commented in an email to Reuters Health that after reviewing this study “as well as CDC and WHO recommendations updated as of 2022, health care providers should be treating C. trachomatis infections with doxycycline 100 mg twice a day for seven days as first-line therapy rather than azithromycin, [given] concerns of increasing macrolide drug resistance against Mycoplasma genitalium and Neisseria gonorrhea.”

“Our clinicians also see the growing uptick of syphilis, gonorrhea, and chlamydia infections in our population, similarly to the rest of the United States since 2020,” she noted. “With the increase in STD infection ... treatment with doxycycline therapy with an important caveat to the patient to complete the one-week treatment regimen is extremely important.”

Dr. Latasha Murphy of the Gynecologic Care Institute at Mercy, Baltimore, also commented in an email to Reuters Health. She noted, “this study does not mirror my clinical experience. More patients have side effects from doxycycline than azithromycin in my experience. Also, anorectal screening is not routine in STD screening.”

“If any major changes to clinical care are made,” she said, “it may be for more consistent screening for anorectal disease. This may ultimately lead to doxycycline being the first line-treatment. More research is needed before making any definitive changes.”

Reuters Health Information © 2022

Doxycycline bests azithromycin for anorectal chlamydia in women