Are beta2 agonists effective for improving symptoms of acute cough or a clinical diagnosis of acute bronchitis without wheeze?
There is insufficient evidence to determine whether beta2 agonists can improve symptoms for children with acute cough or bronchitis with wheeze. Beta2 agonists are not likely to benefit and may cause adverse effects in adults who do not have evidence of airflow restriction (number needed to harm [NNH] = 2).1 (Strength of Recommendation: B, based on inconsistent or limited-quality patient-oriented evidence.)
Cough is a common reason patients seek acute ambulatory care, representing 2.8% of all U.S. office visits in 2012.2 In clinical practice, physicians are most likely to document a diagnosis of acute bronchitis when a patient has lower respiratory tract symptoms, primarily a chest cough, but no clinical evidence suggestive of pneumonia.3 Patients may receive inappropriate medications for acute bronchitis in part because of a discrepancy between patients' expectations of cough duration after an acute respiratory illness (five to nine days) and the typical duration of cough following a respiratory illness (18 days).4
This Cochrane review identified two trials of albuterol in children with acute cough.1 Children with wheezing or other evidence of airflow restriction for which bronchodilator therapy might be clinically indicated were excluded. The trials found no difference between albuterol and placebo in clinical improvement, meaning no decrease in the daily cough impact or number of children with cough. There was also no significant difference in adverse effects between patients given placebo and those given albuterol.
The authors identified five trials of beta2-agonist therapy in adults. When three of the trials were combined, they failed to show a significant difference between beta2 agonists and placebo in cough reduction (in these trials, 19% to 52% of patients had wheezing on initial examination). In subgroup analyses, one trial found that fenoterol (not available in the United States) reduced symptoms by day 2 in patients with evidence of airflow restriction based on physical examination (e.g., wheezing) or testing (e.g., reduced forced expiratory volume in one second, a positive methacholine challenge). This trial also found that patients with a history of smoking or a history of antibiotic treatment had better symptom scores on day 7 if treated with fenoterol than placebo. However, these subgroup findings were not replicated in three other trials.
Adverse effects experienced by adults given beta2 agonists included tremor, shaking, or nervousness (NNH = 2). There are several important limitations to the evidence identified by this Cochrane review. All of the included trials were of short duration (e.g., only three to seven days), raising the possibility that later symptomatic improvement could have been missed. Additionally, only two studies used inhaled beta2 agonists, and participants were not given instructions on the use of spacers.
Guidelines do not recommend using bronchodilators in patients with acute illness who do not have wheezing or a history of chronic obstructive pulmonary disease.5
The practice recommendations in this activity are available at http://www.cochrane.org/CD001726.