Bacterial infections causing acute COPD exacerbations (AECOPD) frequently require antibacterial treatment. More evidence is needed to guide antibiotic choice.

MAESTRAL was a multiregional, randomised, double-blind non-inferiority outpatient study. Patients were ≥60 years, with an Anthonisen type 1 exacerbation, FEV1<60% predicted and ≥2 exacerbations in the last year. Following stratification by steroid use patients received moxifloxacin 400 mg PO q.d. (5-days) or amoxicillin/clavulanic acid 875/125 mg PO b.d. (7-days). The primary endpoint was clinical failure 8-weeks post-therapy in the per protocol (PP) population.Moxifloxacin was non-inferior to amoxicillin/clavulanic acid at the primary endpoint (111/538, 20.6% vs 114/518, 22.0%, 95% CI -5.89, 3.83). In patients with confirmed bacterial AECOPDs, moxifloxacin led to significantly lower clinical failure rates than amoxicillin/clavulanic acid (ITT with pathogens, 62/327, 19.0% vs 85/335, 25.4%, P=0.016).

Confirmed bacterial eradication at EOT was associated with higher clinical cure rates at 8-weeks post-therapy overall (P=0.0014) and for moxifloxacin (P=0.003). Patients treated with oral corticosteroids had more severe disease and higher failure rates.

The MAESTRAL study showed that moxifloxacin was as effective as amoxicillin/clavulanic acid in the treatment of outpatients with AECOPD. Both therapies were well tolerated.