The aim of a study published in Pharmacy World and Science was to determine the efficacy of diphenhydramineagainst cough due to respiratory infection or irritation in patients/subjectswithout comorbidities.

Here, two reviewers independently identified clinicaltrials, randomized trials on diphenhydramine, antitussive agents for cough fromMedline, Embase, Cochrane and references from retrieved articles.

Overall, eleven articles were identified, seven wererejected, leaving only four articles – that were scored 20, 21, 25 and 26 out ofa maximum of 32. In these selected studies, a total of 162 individuals wereexamined – 65 on diphenhydramine, 63 on placebo and 34 in a crossover setting.The crossover studies demonstrated significant effect—27-56% reduction in 20healthy volunteers and 21-26% reduction in 13 patients, in the attenuation ofcough.

Source: Pharmacy World and Science. 2007 Dec;29(6):577-83. doi: 10.1007/s11096-007-9122-2.