Once-daily azithromycin for 3 days compared with clarithromycin for 10 days for acute exacerbation of chronic bronchitis: a multicenter, double-blind, randomized study.

Study objectives: To compare the efficacy and safety of oral azithromycin 500 mg once daily for 3 days with those of oral clarithromycin 500 mg twice daily for 10 days.

Design: Randomized, double-blind, double-dummy, multicenter study.

Setting: Seventy-six study centers in eight countries (Argentina, Brazil, Canada, Chile, Costa Rica, India, South Africa, and USA).

Patients: Three hundred and twenty-two adult outpatients with acute exacerbation of chronic bronchitis (AECB) as documented by increased cough or sputum production, worsening dyspnea, and purulent sputum production.

Interventions: Randomization 1 : 1 to azithromycin 500 mg once daily for 3 days or clarithromycin 500 mg twice daily for 10 days.

Results: The primary efficacy endpoint was clinical response at day 21-24, or test of cure (TOC) visit in the modified intent-to-treat (MITT) analysis (n = 318 patients). The TOC clinical cure rates in the MITT population were equivalent in the two treatment groups at 85% with azithromycin and 82% with clarithromycin (95% CI -5.9%, 12.0%). Clinical success rates on day 10-12 were also equivalent at 93% with azithromycin and 94% with clarithromycin (95% CI -7.9%, 4.4%). Clinical cure rates at TOC by pathogen were equivalent for the two treatment groups for Haemophilus influenzae (azithromycin, 85.7%; clarithromycin, 87.5%), Moraxella catarrhalis (91.7% and 80.0%, respectively) and Streptococcus pneumoniae (90.6% and 77.8%, respectively). Bacteriologic success rates were also equivalent between the azithromycin and clarithromycin treatment groups at TOC for S. pneumoniae (90.6% and 85.2%, respectively), H. influenzae (71.4% and 81.3%, respectively) and M. catarrhalis (100% and 86.7%, respectively). The overall incidence of treatment-related adverse events was similar in the azithromycin and clarithromycin groups (20.9% and 26.8%, respectively), with the most common being abdominal pain (6.3% and 6.1%, respectively), diarrhea (4.4% and 5.5%, respectively), and nausea (4.4% and 3.7%, respectively).

Conclusions: Three-day treatment with azithromycin 500 mg once daily is equivalent to a 10-day treatment with clarithromycin 500 mg twice daily in adult patients with AECB.