Tiotropium Attenuates Refractory Cough and Capsaicin Cough Reflex Sensitivity in Patients with Asthma

Asthmatic cough is often refractory to standard treatments such as inhaled corticosteroids (ICS) and long-acting β₂ agonists (LABA). Tiotropium may modulate cough reflex sensitivity of acute viral cough, but its efficacy in asthmatic cough remains unknown.

To evaluate whether tiotropium improves cough and cough reflex sensitivity in patients with asthma refractory to ICS/LABA.

Seventeen consecutive patients with asthma with chronic cough despite the use of ICS/LABA (13 women; 43.4 ± 19.0 years; average ICS dose, 651 ± 189 μg/d; fluticasone equivalent) were additionally treated with tiotropium (5 μg/d) for 4 to 8 weeks to examine its effects on pulmonary function and capsaicin cough reflex sensitivity (cough thresholds C2 and C5). Cough severity, cough-specific quality of life, and asthma control were also evaluated using cough visual analog scales (VASs), the Japanese version of Leicester Cough Questionnaire (J-LCQ), and Asthma Control Test (ACT), respectively. Patients with an improved cough VAS score of 15 mm or more were considered responders to tiotropium.

Tiotropium significantly improved cough VAS, J-LCQ, and ACT scores, but not FEV₁. Changes in cough VAS score correlated with those in C2 (r = -0.58; P = .03), C5 (r = -0.58; P = .03), and ACT scores (r = -0.62; P = .02), but not in FEV₁ in the overall patients. When analyses were confined to the 11 responders, tiotropium significantly improved capsaicin cough reflex sensitivity within the subgroup (C2: P = .01 and C5: P = .02) and versus the nonresponders (C2: P = .004 and C5: P = .02).

Tiotropium may alleviate asthmatic cough refractory to ICS/LABA by modulating cough reflex sensitivity but not through bronchodilation.