Effects of inhaled corticosteroids on cough threshold in patients with bronchial asthma

In asthmatic subjects cough can be related to the degree of airway inflammation. The aim of this study was to evaluate the effect of treatment with high dose inhaled beclomethasone dipropionate (BDP) on cough threshold in asthmatic subjects. Cough threshold to inhaled capsaicin (one breath of 10(-8)-10(-4)M solution) and to citric acid (one breath of 10(-4)-1 M), expressed as provocative concentration of two (PC2) and four coughs (PC4), was measured in 16 normal and 36 asthmatic subjects. After baseline evaluation, asthmatic subjects were randomized in two groups: (a) Group A, n=20: treated with salbutamol (200 microg t.i.d.) plus BDP (500 microg t.i.d.); (b) Group B, n=16: treated with salbutamol plus placebo in the same doses. After 1 month, cough threshold and clinical and functional evaluation were repeated. After treatment, asthmatics of group A showed a significant improvement in PC4 citric acid, in total symptom and cough scores, and in PD20FEV1 methacholine. In asthmatics of group B, treatment caused no improvement in symptoms, PD20FEV1 methacoline and cough threshold. In addition, cough threshold was not different between normal and asthmatic subjects and, in asthmatics, cough threshold did not correlate with PD20FEV1 methacholine. These data confirm that cough in asthma can be partially related to airway inflammation.