The effectiveness of a traditional Persian medicine preparation in the treatment of chronic cough: A randomized, double-blinded, placebo-controlled clinical trial

[Display omitted] •Chronic cough is a prevalent ailment worldwide.•Persian medicine scholars advised licorice (Glycyrrhiza glabra L.) as an antitussive agent.•Patients were randomized to receive 240 mg daily dose of standardized licorice pastille or placebo for 14 days.•Cough score showed a significant change between verum and placebo groups at the 2-week follow-up time.•Licorice pastille showed a promising effect to alleviate cough using the Leicester Cough Questionnaire. The roots and rhizomes of licorice (Glycyrrhiza glabra L.) are used in traditional Persian medicine for the treatment of numerous diseases. A chronic cough is a non-specific reaction to irritation anywhere in the respiratory system. It usually lasts for more than eight weeks. The current study aimed to evaluate the effect of a modified traditional Persian medicine preparation, licorice pastille, in healing a chronic cough. Through a randomized, double-blinded, placebo-controlled clinical trial was performed in a respiratory disease clinic in Shiraz, Iran; between October 2016 and December 2017. Seventy participants with a chronic cough took part in the trial. The outcome measures were as the daily cough scores (the score being logged via patient symptoms, diary, and the visual analogue scale) and the quality of life measure of chronic cough according to the Leicester Cough Questionnaire. At baseline, there were no significant differences in the demographic or clinical (cough score) characteristics between the two groups. There was complete adherence to protocol in both groups but, the drop-out rate was 4 patients in the placebo and 6 ones in the intervention groups. The results at the end of the trial (Week 2) and follow-up (Week 4) demonstrated the efficacy of the licorice pastille in terms of the cough severity score against the placebo group. This item showed a significant decrease in the intervention group (1.2 ± 0.93) comparing to the placebo one (1.8 ± 1.03) at follow-up time. No major side effects were reported during the study and follow-up time. Licorice pastille could be a promising choice in the treatment of a chronic cough of unknown origin.