Cough threshold for capsaicin increases by azelastine in patients with cough-variant asthma

To assess the effects of azelastine in patients with cough-variant asthma, we measured the cough threshold for capsaicin (the concentration required to elicit more than five coughs) in 16 patients with cough-variant asthma before and after 4 weeks of treatment with azelastine (2 mg; b.i.d.) or placebo. After treatment, coughing decreased in all patients and the cough threshold for capsaicin increased significantly, from 0.67 +/- 0.30 microM to 4.76 +/- 1.55 microM (P < 0.01) in the azelastine group. However, the cough threshold for capsaicin did not increase significantly, from 0.86 +/- 0.33 microM to 1.11 +/- 0.35 microM (P > 0.10) in the placebo group. These results suggest that azelastine inhibits coughing in patients with cough-variant asthma.