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

•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.