The safety and efficacy of clarithromycin in patients with Legionella pneumonia.

Clarithromycin, a new macrolide antibiotic, is at least four times more active in vitro than erythromycin against Legionella pneumophila. In this study the safety and efficacy of orally administered clarithromycin (500 to 1,000 mg bid) in the treatment of Legionella pneumonia were evaluated. Forty-six patients were enrolled in the study, 15 of whom had not responded to previous routine anti-Legionella therapy (erythromycin, ofloxacin, rifampin [rifampicin], or tetracycline). Twelve patients prematurely discontinued the study (nine by the patient's request while feeling well; one because of cancer diagnosis; and two because of adverse events). The response rates after treatment were as follows: clinical cure rate, 98 percent (43/44); clinical success (cure or improved), 100 percent (44/44); radiographic success (cure and improved), 93 percent (28/30); direct antigen fluorescence resolution, 100 percent (40/40); and bacteriologic cure, 100 percent (13/13). Ten patients reported 13 adverse events (seven mild, four moderate, and two severe). Clarithromycin is a safe effective treatment for patients with severe chest infections due to Legionella pneumophila.