Effect of inhaled menthol on citric acid induced cough in normal subjects.

BACKGROUND--Menthol is a commonly used ingredient in many over the counter cough remedies, but there is little objective evidence as to its efficacy. METHODS--Twenty healthy subjects received a cough challenge consisting of five inhalations of 33 mumol citric acid from an air driven dosimeter. The challenge was repeated at hourly intervals for five hours. Five minutes before each challenge subjects inhaled, in a randomised design, either menthol 75% in eucalyptus oil or one of two placebos (pine oil or air). RESULTS--Menthol inhalation caused a reduction in evoked cough when compared with either placebo. CONCLUSIONS--Menthol is an effective antitussive agent in an evoked cough model.