New beta-agonist, KWD 2131, compared with terbutaline in asthmatics. A cumulative dose-response study.

The equipotent bronchodilating doses of terbutaline and a new beta-agonist KWD 2131 with a relatively stronger anti-allergic (inhibition of mediator release) than bronchodilating effect given in nebulized form was estimated in eight patients with intrinsic asthma. The subthreshold bronchodilating dose of KWD 2131 was also evaluated. The study was a 2-day, single-blind cross-over comparison between cumulative doses of KWD 2131 (0.5 mg to 12 mg) and terbutaline (0.05 mg to 1.2 mg). Both drugs gave a dose-dependent bronchodilating effect as measured spirometrically. It was already statistically significant at the 0.05 mg dose of terbutaline, but not until the cumulative 1.5 mg dose (0.5 + 1 mg) of KWD 2131. The median value of the bronchodilating potency of terbutaline relative to KWD 2131 was 30. The influence of the two substances on tremor and the cardiovascular system was minimum and clinically unimportant. The search for the subthreshold bronchodilating dose of KWD 2131 was of interest, as this dose was to be used in a subsequent antigen provocation study in order to selectively evaluate KWD 2131's anti-allergic property. The mean subthreshold bronchodilating dose of KWD 2131 was 1 mg. However, four of the eight patients showed bronchodilatation at the 1 mg dose, and two of the four also at 0.5 mg.