Amoxicillin-clavulanate versus azithromycin for respiratory exacerbations in children with bronchiectasis (BEST-2): a multicentre, double-blind, non-inferiority, randomised controlled trial.

Background: Although amoxicillin-clavulanate is the recommended first-line empirical oral antibiotic treatment for non-severe exacerbations in children with bronchiectasis, azithromycin is also often prescribed for its convenient once-daily dosing. No randomised controlled trials involving acute exacerbations in children with bronchiectasis have been published to our knowledge. We hypothesised that azithromycin is non-inferior to amoxicillin-clavulanate for resolving exacerbations in children with bronchiectasis.

Methods: We did this parallel-group, double-dummy, double-blind, non-inferiority randomised controlled trial in three Australian and one New Zealand hospital between April, 2012, and August, 2016. We enrolled children aged 1-19 years with radiographically proven bronchiectasis unrelated to cystic fibrosis. At the start of an exacerbation, children were randomly assigned to oral suspensions of either amoxicillin-clavulanate (22·5 mg/kg, twice daily) and placebo or azithromycin (5 mg/kg per day) and placebo for 21 days. We used permuted block randomisation (stratified by age, site, and cause) with concealed allocation. The primary outcome was resolution of exacerbation (defined as a return to baseline) by 21 days in the per-protocol population, with a non-inferiority margin of -20%. We assessed several secondary outcomes including duration of exacerbation, time to next exacerbation, laboratory, respiratory, and quality-of-life measurements, and microbiology. This trial was registered with the Australian/New Zealand Registry (ACTRN12612000010897).

Findings: We screened 604 children and enrolled 236. 179 children had an exacerbation and were assigned to treatment: 97 to amoxicillin-clavulanate, 82 to azithromycin). By day 21, 61 (84%) of 73 exacerbations had resolved in the azithromycin group versus 73 (84%) of 87 in the amoxicillin-clavulanate group. The risk difference showed non-inferiority (-0·3%, 95% CI -11·8 to 11·1). Exacerbations were significantly shorter in the amoxicillin-clavulanate group than in the azithromycin group (median 10 days [IQR 6-15] vs 14 days [8-16]; p=0·014). Adverse events were attributed to the trial medication in 17 (21%) of 82 children in the azithromycin group versus 23 (24%) of 97 in the amoxicillin-clavulanate group (relative risk 0·9, 95% CI 0·5 to 1·5).

Interpretation: By 21 days of treatment, azithromycin is non-inferior to amoxicillin-clavulanate for resolving exacerbations in children with non-severe bronchiectasis. In some patients, such as those with penicillin hypersensitivity or those likely to have poor adherence, azithromycin provides another option for treating exacerbations, but must be balanced with risk of treatment failure (within a 20% margin), longer exacerbation duration, and the risk of inducing macrolide resistance.

Funding: Australian National Health and Medical Research Council.