A Cochrane review [Abstract] 1 included 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).
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and byindirectness (short duration of interventions; modern inhalation administration not studied).
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