Beta2-agonists for acute bronchitis

There are no clearly effective treatments for the cough of acute bronchitis, and beta2-agonists are often prescribed, perhaps because clinicians suspect many patients also have reversible airflow restriction contributing to the symptoms.

To determine whether beta2-agonists improve symptoms of acute bronchitis in patients who do not have underlying pulmonary disease.

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2005), MEDLINE (January 1966 to November 2005) and EMBASE (1974 to November 2005).

Trials in which patients (adults or children over two years of age) who were diagnosed with acute bronchitis or acute cough (without known pulmonary disease and without other cause) were randomized to beta2-agonist versus placebo, no treatment or alternative treatment.

Three authors independently selected outcomes and evaluated trial quality while blinded to study results, they then extracted data. Trials in children and in adults were analyzed separately.

Two trials in children (n = 109) with acute cough and no evidence of airway obstruction did not find any benefits from beta2-agonists. Combined data did not show a significant difference in daily cough scores between patients given oral beta2-agonists and those in the control groups. Five trials in adults (n = 418) with acute cough or acute bronchitis had mixed results but overall summary statistics did not reveal any significant benefits from oral (three trials) nor inhaled (two trials) beta2-agonists. There were no significant differences in daily cough scores nor in the number of patients still coughing after seven days (control rate 73%; relative risks (RR) 0.77, 95% CI 0.54 to 1.09). Subgroups of patients with evidence of airflow limitation had lower symptom scores if given beta2-agonists, in one trial. Furthermore, the trials that did note quicker resolution of cough in patients given beta2-agonists were those that had a higher proportion of patients with wheezing at baseline. Patients given beta2-agonists were more likely to report tremor, shakiness or nervousness than patients in the control groups (for trials in children: control rate 0%; RR 6.76, 95% CI 0.86 to 53.12; number needed to harm (NNH) 9, 95% CI 5 to 100; for trials in adults: control rate 11%; RR 7.94, 95% CI 1.17 to 53.94; NNH 2.3, 95% CI 2 to 3).

There is no evidence to support the use of beta2-agonists in children with acute cough who do not have evidence of airflow obstruction. 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 patients with evidence of airflow obstruction. However, this potential benefit is not well-supported by the available data and must be weighed against the adverse effects associated with beta2-agonists.