Azithromycin may be riskier than previously thought. A report in the May 17 New England Journal of Medicine finds that patients taking a five-day course of the broad-spectrum antibiotic azithromycin, especially those at greatest risk for cardiovascular disease, are at increased risk for sudden cardiac death, compared with patients who took no antibiotics or the antibiotics amoxicillin and ciprofloxacin. Azithromycin is related to erythromycin and clarithromycin, which are known to increase risk of sudden cardiac death, but azithromycin was thought to be safer. Data from Medicaid patients prescribed azithromycin for five days between 1992 and 2006 revealed an estimated 47 additional cardiovascular deaths per million courses of treatment, and among patients at greatest risk for cardiovascular disease who took azithromycin there were 245 more deaths per million courses.