Oral capsaicin as treatment for unexplained chronic cough and airway symptoms

Background Unexplained Chronic Cough (UCC) is characterized by persistent coughing without evident medical explanation. Research question Does daily oral administration of natural capsaicin (chili) improve refractory coughing in patients with UCC? Study Design and Methods Forty-six patients (mean age, 60.5 years) with UCC participated in this crossover, randomized, double-blind study.For 4 weeks, the participants took capsules containing pure capsaicin orally, and after a washout of 2 weeks, took placebo capsules for 4 weeks.A capsaicin inhalation cough test was used to assess the capsaicin concentrations required to reach two coughs (C2) and five coughs (C5). The number of coughs in a 24-h period and the number of coughs per hour were recorded on four occasions using the Leicester Cough Monitor (LCM). Participants completed questionnaires with items on cough, cough-related symptoms, and quality of life. Results The mean values for C2 and C5 increased after the capsaicin treatment period, as compared to the first visit (baseline) (P<0.05 and P<0.03, respectively), although they did not differ from the placebo recordings.Neither the capsaicin nor the placebo treatment significantly reduced the cough frequency and did not differ between the two treatment periods. When dividing the participants in Low coughers (≤400 coughs within 24-h) respective High coughers (>400 cough) the Low coughers experienced a significantly better outcome from capsaicin but not from placebo.The Visual Analog Scale (VAS) symptom scores improved following capsaicin treatment compared with baseline and placebo treatment, in terms of the frequencies of coughing (P<0.001), rhinitis (P<0.03) and throat irritation (P<0.01). The Leicester Cough Questionnaire (LCQ-S) improved after capsaicin treatment compared to baseline and compared to the placebo treatment for all the domains (P<0.01 for the total score). Interpretation Capsaicin powder taken orally is clinically effective and well-tolerated by patients with UCC. The results suggest a future treatment for UCC.