Lorne A Becker, Jeffrey Hom, Miguel Villasis‐Keever, Johannes C van der Wouden

The diagnosis of acute bronchitis is made on clinical grounds and a variety of clinical definitions have been used. There are no clearly effective treatments for the cough of acute bronchitis. Beta2-agonists are often prescribed, perhaps because clinicians suspect many patients also have reversible airflow restriction (as seen in asthma or chronic obstructive pulmonary disease (COPD)) contributing to the symptoms. To determine whether beta2-agonists improve acute bronchitis symptoms in people with no underlying pulmonary disease (such as asthma, COPD or pulmonary fibrosis). We searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2015, Issue 5, MEDLINE (January 1966 to May 2015), EMBASE (1974 to May 2015), Web of Science (2011 to May 2015) and LILACS (1982 to May 2015). Randomised controlled trials (RCTs) which allocated people (adults, or children over two years of age) with acute bronchitis or acute cough and without known pulmonary disease to beta2-agonist versus placebo, no treatment or alternative treatment. Three review authors independently selected outcomes and extracted data while blinded to study results. Two review authors independently assessed each trial for risk of bias. We analysed trials in children and adults separately. Two trials of moderate quality in children (n = 134) with no evidence of airflow restriction did not find any benefits from oral beta2-agonists. Five trials in adults (n = 418) had mixed results but overall summary statistics did not reveal any significant benefits from oral (three trials) nor from inhaled (two trials) beta2-agonists. Three studies with low-quality evidence demonstrated no significant differences in daily cough scores, nor in the percentage of adults still coughing after seven days (control group 71%; risk ratio (RR) 0.86, 95% confidence interval (CI) 0.63 to 1.18; 220 participants). In one trial, subgroups with evidence of airflow limitation had lower symptom scores if given beta2-agonists. The trials that noted quicker resolution of cough with beta2-agonists were those with a higher proportion of people wheezing at baseline. Low-quality evidence suggests that adults given beta2-agonists were more likely to report tremor, shakiness or nervousness (RR 7.94, 95% CI 1.17 to 53.94; 211 participants; number needed to treat for an additional harmful outcome (NNTH) 2). There is no evidence to support the use of beta2-agonists in children with acute cough who do not have evidence of airflow restriction. There is also little evidence that the routine use of beta2-agonists is helpful for adults with acute cough. These agents may reduce symptoms, including cough, in people with evidence of airflow restriction. However, this potential benefit is not well supported by the available data and must be weighed against the adverse effects associated with their use.