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 μmto 4.76±1.55 μm(P<0.01) in the azelastine group. However, the cough threshold for capsaicin did not increase significantly, from 0.86±0.33 μmto 1.11±0.35 μm(P>0.10) in the placebo group. These results suggest that azelastine inhibits coughing in patients with cough-variant asthma.