Objective: To demonstrate that 5 days of treatment with a new fluoroquinolone, gemifloxacin, is at least as effective as 7 days of treatment with levofloxacin in adult patients with acute exacerbation of chronic bronchitis (AECB).

Design: Randomized, double-blind, double dummy, multicentre, parallel group study

Setting: Sixty different medical centers in US, UK and Germany.

Material and methods: A total of 360 adults (>40years of age) with AECB were randomly assigned to receive gemifloxacin 320mg once daily for 5 days or levofloxacin 500mg once daily for 7 days. The primary efficacy parameter was a clinical response at follow-up (Days 14–21).

Results: In total, 335/360 patients completed the study (93.1%). Seven patients receiving gemifloxacin withdrew from the study compared to 18 patients receiving levofloxacin; this difference was statistically significant (Fisher's exact test: p=0.02). In the intent-to-treat (ITT) population, the clinical success rate at follow-up (Days 14–21) was 85.2% (155/182) with gemifloxacin and 78.1% (139/178) with levofloxacin. Clinical success rate in the per-protocol (PP) population was 88.2% (134/152) with gemifloxacin and 85.1% (126/148) with levofloxacin. At long-term follow-up (Days 28–35), the clinical success rates in the PP population were 83.7% (123/147) with gemifloxacin and 78.4% (109/139) with levofloxacin. The difference in success rates was 5.26% (95% CI: −3.83, 14.34).

Conclusion: The clinical efficacy of gemifloxacin 320mg once daily for 5 days in AECB was at least as good as levofloxacin 500mg once daily for 7 days. Fewer withdrawals and superior clinical efficacy at long-term follow-up were also seen with gemifloxacin.