Phase III, randomized, double-blind study of clarithromycin extended-release and immediate-release formulations in the treatment of patients with acute exacerbation of chronic bronchitis

Background: Clarithromycin has an established efficacy and safety profile i n the treatment of respiratory tract infections. Objective: The purpose of this study was to compare the clinical and bacter iologic efficacy and tolerability of clarithromycin extended-release and im mediate-release formulations in patients with acute exacerbation of chronic bronchitis (AECB). Methods: In a phase III, randomized, double-blind, parallel-group, multicen ter study, patients aged greater than or equal to 12 years with signs and s ymptoms of AECB and a productive cough with purulent sputum received treatm ent with extended-release (two 500-mg tablets once daily) or immediate-rele ase (one 500-mg tablet twice daily) clarithromycin for 7 days. Assessments were performed before treatment, within 48 hours after treatment, and at th e test-of-cure visit (study days 19-21). Patients who took greater than or equal to1 dose of study drug were included in the safety analysis. Results: Of 620 patients randomized and treated, 182 were clinically and ba cteriologically assessable (100 in the extended-release group and 82 in the immediate-release group). Treatment groups were well matched with respect to demographic characteristics and medical and social history. At the test- of-cure visit, 83% (83/100) of patients in the extended-release and 82% (67 /82) of patients in the immediate-release group achieved clinical cure; 86% (85/99) and 85% (70/82), respectively, demonstrated bacteriologic cure. Ov erall pathogen eradication rates were 86% (100/116) in the extended-release group and 88% (86/98) in the immediate-release group. The most frequently reported ad-verse events were diarrhea (6% in extended-release group vs 4% in immediate-release group; no significant difference), taste alterations ( 4% in each group), and nausea (3% in each group); no clinically meaningful changes in laboratory values or vital signs, as assessed by the investigato r, were observed. Conclusion: This study suggests that clarithromycin extended-release and im mediate-release formulations have equivalent clinical and bacteriologic eff icacy and tolerability in patients with AECB.