Efficacy of major chlamydia drug confirmed

In a study published Dec. 24 in the New England Journal of Medicine, the research team compared two of the most commonly used medications for urogenital chlamydia -- a single dose of azithromycin versus doxycycline given twice daily for seven days. Azithromycin had a cure rate of 97 percent, against a 100 percent cure rate for doxycycline.

"Recent studies have raised concerns over the efficacy of azithromycin, and there has not been a definitive, well-controlled randomized clinical trial of its effectiveness," said William M. Geisler, M.D., professor in the Division of Infectious Diseases in the UAB Department of Medicine and principal investigator of the study. "For physicians, knowing whether azithromycin is an effective treatment option is important because patient adherence to therapy with doxycycline can be an issue. Azithromycin requires only one dose, while doxycycline requires patients to take multiple pills over seven days.

Studies have shown that patients are much more likely to be adherent to therapy when taking a single dose compared to multiple doses over time. Failure to take all of a prescribed medicine can allow the condition being treated to persist.

Geisler's team partnered with researchers at the University of Southern California and the Los Angeles County Department of Health Services. They enrolled 567 male and female subjects ages 12-21 with chlamydia residing in long-term, gender-segregated youth correctional facilities in Los Angeles. Half were given azithromycin and half doxycycline.

Studies of sexually transmitted diseases can be difficult to do. Medical providers often cannot monitor adherence to a drug regimen and a successfully treated patient can become re-infected -- often from the same partner -- during the course of therapy.

"The design of this study allowed us to control for all the complicated variables that had hindered previous research projects of this nature," Geisler said. "Our study subjects were separated from previous partners and had limited sexual exposure. This approach allowed us to truly understand how well these drugs worked."

There were five treatment failures among those taking azithromycin and no treatment failures among the doxycycline group.

"The bottom line is that our results show that both medications are effective in the treatment of chlamydia, and that while azithromycin had a limited number of treatment failures, the adherence to the drug regimen is likely to be much greater with the single-dose drug as opposed to the multidose doxycycline," Geisler said.

Geisler, who has written the Centers for Disease Control and Prevention guidelines for chlamydia therapy since 2006, says this study confirmed that azithromycin should still be considered a front-line therapy, especially when drug adherence is a factor.

Geisler says the side-effect profile -- mainly gastrointestinal discomfort -- is similar for both drugs. Cost can vary, with azithromycin typically a little less expensive than doxycycline.

More than 1.4 million cases of chlamydia are reported to the CDC each year. It is the most commonly reported sexually transmitted disease, and Geisler says estimates suggest that up to another 1.4 million cases go unreported every year.