MINNEAPOLIS – Azithromycin and doxycycline appear to be equally effective for men with nongonococcal urethritis.
In a randomized placebo-controlled trial, both drugs had good overall effectiveness, with an 84% clinical cure rate for azithromycin and a 78% rate for doxycycline. But some pathogens were more resistant to the drugs than others, Lisa Manhart, Ph.D., said at a conference on STD prevention sponsored by the Centers for Disease Control and Prevention.
The Mycoplasma Genitalium Antibiotic Susceptibility and Treatment (MEGA) trial enrolled 606 men with nongonococcal urethritis from 2007 to 2011. The main end points of the trial were clinical and microbiological cure of urethritis associated with M. genitalium infection, when treated with the standard therapy recommended by the Centers for Disease Control and Prevention: a single dose of 1 g of azithromycin, or a 7-day regimen of 100 mg of doxycycline taken twice a day.
Several pathogens cause nongonococcal urethritis, said Dr. Manhart, an epidemiologist at the University of Washington, Seattle. Among them are Chlamydia trachomatis, M. genitalium, the recently differentiated Ureaplasma urealyticum, and Trichomonas vaginalis. In some infections, no pathogen can be identified. In addition to presenting the end points for M. genitalium infections, Dr. Manhart broke the results out by other pathogens.
The mean age of the men in the trial was 34 years. Most (67%) were heterosexual, 28% were homosexual, and about 5% were bisexual. They reported a mean of six sexual partners in the past 12 months.
The most common infectious pathogen was chlamydia (26%), followed by U. urealyticum (24%). M. genitalium was present in 14% of the study group, and T. vaginalis in 2%. The remainder of the group had an idiopathic urethritis.
Treatment consisted of either a placebo azithromycin and active doxycycline or active azithromycin and placebo doxycycline. If men still showed symptoms or microbiological failure after treatment, they were offered reverse therapy (i.e., a treatment pack with the opposite active and placebo drugs), and returned for a follow-up visit in 3 weeks. If they were still not clinically or microbiologically cured, they received a course of moxifloxacin.
Overall, there was no statistically significant difference in cure rates between the two drugs. Nor were there significant differences among men with chlamydia infections, with a clinical cure rate of 87% for azithromycin and 78% for doxycycline. For microbiological cure, the rates were 86% and 90%, respectively.
Both clinical and microbiological cures rates were much lower in men infected with M. genitalium, but the rates were not significantly different between the two drugs. Clinical cure rates were 68% for azithromycin and 48% for doxycycline. For microbiological cure, the rates were 39% and 30%, respectively.
Men with U. urealyticum infections fared a little better, but again, the cure rates were not significantly different between the drugs. A clinical cure occurred in 85% of the azithromycin group and 75% of the doxycycline group. Microbiological cure rates were 75% and 69%, respectively.
For those with idiopathic urethritis, the cure rate for both drugs was identical: 87%.
Reverse therapy was still not effective in some men with U. urealyticum or M. genitalium infections. Three weeks after that treatment, 51% of those with M. genitalium and 57% of those with U. urealyticum were still positive for the pathogen. These men received a course of moxifloxacin.
"Moxifloxacin was quite effective, but at the end of the trial, we still had two men with M. genitalium and four with U. urealyticum who did not clear their infections," Dr. Manhart said.
Moxifloxacin, although highly effective, is too expensive to be used as first-time therapy in a public health department setting, she noted. "Its preinsurance cost runs up to $150, so we are still faced with a conundrum when treating these infections."
Dr. Manhart had no financial declarations.