Bronchial and cardiovascular responses to inhaled reproterol in asthmatics: a double-blind placebo controlled dose-response study.

Reproterol is a synthetic selective beta-adrenoceptor agonist with a xanthine side chain. The bronchial and cardiovascular responses to inhaled reproterol were studied in 14 asthmatics. The study was placebo controlled and double-blind, comparing doubling doses of reproterol from 500 micrograms-8 mg. The peak improvement in FEV1 showed a non-linear dose-response, with an initial plateau at the 1 mg dose producing a mean increase in FEV1 of 17%, but significant further improvement at the 8 mg dose, producing a mean improvement of 29% in FEV1. The time taken for improvement in airways obstruction to start shortened with increasing doses. The duration of bronchodilation was dose-dependent, with the 8 mg dose showing a significantly longer duration of action than the lower doses. The time to drop below 75% of the maximum achieved bronchodilation was 125 min, and was independent of the dose. There were no significant changes in pulse or blood pressure at any dose. The study shows that reproterol is a well tolerated selective beta 2-adrenoceptor agonist whose duration of action and peak effect can be significantly increased by increasing the dose to 8 mg, without producing more unwanted effects.