Six RCTs (n=1,681 participants) were included in the review, including two unpublished trials. Sample sizes ranged from 60 to 476 participants. The quality of included trials was reported to be generally good (three trials achieved the maximum score of 5 points). Four RCTs (n=1,012) of adult participants were eligible for inclusion in the meta-analysis for herbal medicine versus placebo. A fifth trial conducted in children was excluded from this meta-analysis.
Herbal medicine versus placebo (four trials): All trials were carried out with adults. The pooled estimate showed a statistically significant reduction in the Bronchitis Severity Score score in patients receiving Pelargonium sidoides treatment compared with those receiving placebo (WMD 2.80 points, 95% CI 2.44 to 3.15). Heterogeneity was reported (I2= 54.4%; p=0.09). The small number of trials meant that it was not possible to produce a useful funnel plot. Statistical significance in the Bronchitis Severity Score in patients was maintained when the unpublished study was removed from the analysis (WMD 2.48 points, 95% CI 2.05 to 2.92) and heterogeneity was reduced (I2=0%; p=0.67). Positive effects were noted in the treatment groups for a number of secondary outcomes including: participant health status; speed of onset of treatment effect; duration of illness; improvements in individual components of Bronchitis Severity Score; quality of life; patient satisfaction; and complete recovery at day seven.
Herbal medicine versus conventional treatment (one trial; Jadad score of 2 points): In children aged between six and 12 years, bronchitis specific symptoms were reduced more effectively in those receiving Pelargonium sidoides treatment than in those receiving acetylcysteine, but the difference between the groups was not significant.
No mild or serious adverse events were reported in the five RCTs that supplied information.