Cough desensitization treatment: A randomized, sham-controlled pilot trial for patients with refractory chronic cough

The purpose of this study was to determine feasibility of treating refractory chronic cough (RCC) with progressive doses of capsaicin paired with cough suppression.

In this sham-controlled, parallel RCT, 14 adults with RCC were randomly assigned to either behavioral cough suppression therapy (BCST) plus 6 treatment sessions involving exposure to nebulized capsaicin in progressively larger concentrations while actively suppressing cough (n = 8), or BCST plus 6 sessions of exposure to a single subthreshold dose of capsaicin (sham; n = 6). The Leicester Cough Questionnaire (LCQ) was the primary outcome measure. Urge-to-cough (UTC) testing, measuring both UTC and cough frequency, served as secondary outcome measures. Data was analyzed with mixed effects linear regression and follow-up contrasts.

Results on all measures favored the treatment group; however, there was only strong evidence of a difference in treatment effect on cough frequency during UTC testing. Mean change in LCQ at 3-weeks post treatment was 2.95 and 1.75 (p = .23), in the treatment and sham groups, respectively. Cough frequency during UTC testing reduced by 97% and 56% (p < .0001) at three weeks post, respectively. Within-group comparisons revealed strong evidence of change in the treatment group (p < .001) and moderate evidence of a change in the sham group (p = .08) in LCQ.

Conclusions from this study are limited due to the very small sample size; however, the study provides feasibility and proof-of-concept evidence to support further investigation of treating RCC with repeated exposure to nebulized capsaicin paired with BCST.