Comparison of three-day and five-day courses of azithromycin in the treatment of atypical pneumonia.

This open, randomised clinical study, conducted from June 1988 to December 1989, included 84 patients with clinical and radiological findings of atypical pneumonia. All patients were treated with a total dose of 1.5 g azithromycin, a new azalide antibiotic. In Group I, azithromycin was administered for three days (500 mg once daily). In Group II, azithromycin was administered for five days (250 mg b.i.d. on day 1, followed by 250 mg once daily on days 2 to 5). Causative pathogens were identified by serological methods. Of the 41 patients in Group I, Mycoplasma pneumoniae, Chlamydia psittaci and Coxiella burnetti were identified in 19, 4 and 3 patients, respectively. In Group II there were 43 patients; Mycoplasma pneumoniae was identified in 24, Chlamydia psittaci in 4 and Coxiella burnetti in 3. Only patients with known causative pathogens were included in the evaluation of clinical efficacy. All patients were clinically cured by day 5; most of the patients became afebrile within 48 h of starting treatment. Side effects were observed in one patient in Group I and in one patient in Group II. The results suggest that a 1.5 g total dose of azithromycin is equally effective when administered as a three- or five-day regimen for the treatment of atypical pneumonia.