Original Research Article

Treatments in Respiratory Medicine

, Volume 4, Issue 1, pp 31-39

First online:

Once-Daily Azithromycin for 3 Days Compared with Clarithromycin for 10 Days for Acute Exacerbation of Chronic Bronchitis

A Multicenter, Double-Blind, Randomized Study
  • Robert N. SwansonAffiliated withPfizer Global Research & Development
  • , Alberto Lainez-VentosillaAffiliated withInstituto Costarricense de Investigaciones Clinicas (ICIC), Urbanizacion Los Arboles, Frente al Centro Nacional de Rehabilitacion (CENARE)
  • , Maria C. De SalvoAffiliated withHospital General de Agudos
  • , Michael W. DunneAffiliated withPfizer Global Research & Development
  • , Guy W. AmsdenAffiliated withClinical Pharmacology Research Center, Bassett Healthcare Email author 

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Study objectives

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


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


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


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.


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


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).


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