Analysis of the evidence of efficacy and safety of over-the-counter cough medications registered in Brazil

The objective of this study was to analyze the level of evidence regarding the efficacy, effectiveness and safety of over-the-counter (OTC) cough medications registered in Brazil. The National Health Surveillance Agency database was used to identify the drugs. Clinical trials, systematic reviews, meta-analyses, and studies on safety were searched on the Medline baseline, the Cochrane Library and SIETES (System of Essential Information in Therapeutics and Health; database in Spanish). Most drugs (62.5%) were sold as a fixed-dose combination of two or more drugs. Randomized clinical trials were found for only three drugs: bromhexine, dextromethorphan and guaifenesin. No clinical trials were found for fixed-dose combinations. Systematic reviews on Cochrane did not report any evidence in favor of or against the effectiveness of cough drugs. Efficacy is also unclear, especially regarding fixed-dose combinations. The evidence for the efficacy of OTC cough medications available in Brazil is poor due to the lack of quality studies. Pharmacovigilance of OTC cough medications should be encouraged.