Abstract: We did not identify any new trials for inclusion in this 2017 update. We included 17 trials with 5099 participants in the primary analysis. The quality of trials was generally good. At follow-up there was no difference in participants described as being clinically improved between the antibiotic and placebo groups (11 studies with 3841 participants, risk ratio (RR) 1.07, 95% confidence interval (CI) 0.99 to 1.15). Participants given antibiotics were less likely to have a cough (4 studies with 275 participants, RR 0.64, 95% CI 0.49 to 0.85; number needed to treat for an additional beneficial outcome (NNTB) 6) and a night cough (4 studies with 538 participants, RR 0.67, 95% CI 0.54 to 0.83; NNTB 7). Participants given antibiotics had a shorter mean cough duration (7 studies with 2776 participants, mean difference (MD) -0.46 days, 95% CI -0.87 to -0.04). The differences in presence of a productive cough at follow-up and MD of productive cough did not reach statistical significance. Antibiotic-treated participants were more likely to be improved according to clinician's global assessment (6 studies with 891 participants, RR 0.61, 95% CI 0.48 to 0.79; NNTB 11) and were less likely to have an abnormal lung exam (5 studies with 613 participants, RR 0.54, 95% CI 0.41 to 0.70; NNTB 6). Antibiotic-treated participants also had a reduction in days feeling ill (5 studies with 809 participants, MD -0.64 days, 95% CI -1.16 to -0.13) and days with impaired activity (6 studies with 767 participants, MD -0.49 days, 95% CI -0.94 to -0.04). The differences in proportions with activity limitations at follow-up did not reach statistical significance. There was a significant trend towards an increase in adverse effects in the antibiotic group (12 studies with 3496 participants, RR 1.20, 95% CI 1.05 to 1.36; NNT for an additional harmful outcome 24). There is limited evidence of clinical benefit to support the use of antibiotics in acute bronchitis. Antibiotics may have a modest beneficial effect in some patients such as frail, elderly people with multimorbidity who may not have been included in trials to date. However, the magnitude of this benefit needs to be considered in the broader context of potential side effects, medicalisation for a self limiting condition, increased resistance to respiratory pathogens, and cost of antibiotic treatment.

Plain-language summary: We included randomised controlled trials comparing any antibiotic therapy with placebo or no treatment in people with acute bronchitis or acute productive cough and no underlying chronic lung condition. We included 17 trials with 5099 participants. Co-treatments with other medications to relieve symptoms were allowed if they were given to all participants in the study. Our evidence is current to 13 January, 2017. We found limited evidence of clinical benefit to support the use of antibiotics for acute bronchitis. Some people treated with antibiotics recovered a bit more quickly with reduced cough-related outcomes. However, this difference may not be of practical importance as it amounted to a difference of half a day over an 8- to 10-day period. There was a small but significant increase in adverse side effects in people treated with antibiotics. The most commonly reported side effects included nausea, vomiting, diarrhoea, headache, and rash. This review suggests that there is limited benefit to the patient in using antibiotics for acute bronchitis in otherwise healthy individuals. More research is needed on the effects of using antibiotics for acute bronchitis in frail, elderly people with multiple chronic conditions who may not have been included in the existing trials. Antibiotic use needs to be considered in the context of the potential side effects, medicalisation for a self limiting condition, cost of antibiotic treatment, and in particular associated population-level harms due to increasing antibiotic resistance. The quality of these trials was generally good, particularly for more recent studies.