The present study will compare the antitussive effects of dextromethorphan (30 mg) plus salbutamol (2 mg), along with dextromethorphan (30 mg) alone and placebo on artificial cough that was induced by citric acid in nineteen healthy non-smoking volunteers in a crossover double-blind study.

The method used was inhaled citric acid with increasing concentrations to start the cough threshold level. The inhaled citric acid showed an acceptable reproducibility and demonstrated to be appropriate for comparison of antitussive drugs. The cough threshold level was evaluated before in addition to 90 and 180 minutes after each medication. After placebo, the cough threshold level did not show any significant increase. But, significant increases were observed following dextromethorphan and the dextromethorphan-salbutamol combination. Among the treatment regimes, significant differences were seen in favor of the dextromethorphan-salbutamol combination. The results of the study specified that salbutamol has antitussive action that improves the effect of plain dextromethorphan.

Source: Karttunen P, Tukiainen H, Silvasti M, Kolonen S. Antitussive effect of dextromethorphan and dextromethorphan-salbutamol combination in healthy volunteers with artificially induced cough. Respiration. 1987;52(1):49-53.