Inhaled corticosteroids decrease cough reflex sensitivity to capsaicin in asthmatics but not in patients with COPD

Cough is a common symptom in asthma and COPD. Few studies, yielding contrasting data, have evaluated the effect of inhaled corticosteroids (ICS) on cough reflex sensitivity in subjects with asthma and COPD. Aim of the study was to evaluate the effect of treatment with ICS on cough reflex sensitivity in patients with asthma and COPD. Methods: 25 patients with mild to moderate asthma and 27 with moderate to severe COPD were enrolled. None of the patients had used inhaled or oral corticosteroids for at least one month prior to the study. After baseline evaluation patients were randomized into groups: asthmatics – group 1 (n=15) treated with budesonide (400 mcg b.i.d) and salbutamol (200 mcg as-needed), group 2 (n=10) treated with placebo and salbutamol; COPD patients – group 3 (n=17) treated with budesonide (400 mcg b.i.d) and salbutamol (200 mcg as-needed) and group 4 (n=10) treated with placebo and salbutamol. All groups received four weeks of therapy. Capsaicin aerosol was given in order of ascending concentration until the concentrations inducing 2 or more (C2) and 5 or more coughs (C5) were attained. Results: after treatment, C5 significantly increased (i.e., cough reflex sensitivity decreased) in asthmatic subjects of group 1 (logC5 1.52±0.24; 2.08±0.22µM mean ± SEM p=0.020) but did not change in group 2 (logC5 2.13±0.33; 2.16± 0.32µM p=0.823). C2 did not significantly change in either asthma group. There were no significant changes in C2 and C5 after treatment in patients with COPD of group 3 and 4. Conclusion: Our data demonstrate that four weeks of therapy with ICS decreases cough reflex sensitivity to capsaicin in patients with asthma, but not in those with COPD.