Antitussive effect of azelastine hydrochloride in patients with bronchial asthma.

To investigate the efficacy of azelastine hydrochloride (azelastine, CAS 79307-93-0, Azeptin) in suppressing cough, 22 bronchial asthma patients complaining mainly of cough were given the drug for four weeks. Peak flow rates (PEFR), pulmonary function tests, capsaicin cough threshold, and bronchial hyperresponsiveness were compared pre- and post-administration. After four-week's administration of azelastine (2 mg twice daily), cough decreased as demonstrated in a significant progressive improvement of cough points. The morning PEFR (1/min) was improved significantly at one week and two weeks post-administration. Changes were from 434 +/- 26.4 pre-administration to 461 +/- 25.8 at Week 1 (p < 0.05), 462 +/- 26.7 at Week 2 (p < 0.05), 452 +/- 22.5 at Week 3, and 462 +/- 20.8 at Week 4. The evening PEFR (1/min) showed 439 +/- 22.2 pre-administration, 454 +/- 21.4 at Week 1, 464 +/- 22.4 at Week 2, 457 +/- 19.3 at Week 3 and 467 +/- 17.8 at Week 4, improvement being significant at Week 1 (p < 0.05). Regarding pulmonary function tests no significant changes were observed. FVC (liter), FEV1 (liter), and FEV1/FVC (%) were 3.45 +/- 0.86, 2.68 +/- 0.52, and 83.6 +/- 5.93 pre-administration; and 3.48 +/- 0.21, 2.72 +/- 0.65, and 84.1 +/- 6.21 post-administration, respectively. The capsaicin cough threshold [Ccap (mumol/l)] showed significant improvement, changing from 5.95 (0.016-50.0) pre-administration to 19.7 (0.08-50.0) post-administration (p < 0.05). Conversely, an index of bronchial hyperresponsiveness, Dmin (mg/dl;U), showed no significant changes (14.9 +/- 5.2 vs. 19.7 +/- 5.3). These results suggest that azelastine inhibits cough in patients with bronchial asthma by increasing the level of the cough threshold without changing bronchial hyperresponsiveness.