Assessment of bronchial effects following topical administration of butylamino‐phenoxy‐propanol‐acetate, an oculoselective beta‐ adrenoceptor blocker in asthmatic subjects.

Abstract

1. Butylamino‐phenoxy‐propanol‐acetate (BPPA) is a new topical oculoselective beta‐adrenoceptor blocker for the reduction of intraocular pressure (IOP) in man. Its potency on the airways of normal subjects was identical with that of placebo. A study was carried out to determine the potential of BPPA to cause bronchoconstriction in mild asthmatics (FEV1 greater than or equal to 60% predicted) with normal IOP. 2. Twelve nonsmoking outpatients who bronchoconstricted to 0.25 or 0.50% of timolol eye drops (fall in FEV1 23.33 +/‐ 1.20% (mean +/‐ s.e. mean), range 16‐30) were investigated in this double‐masked, randomized, 3‐period, crossover study. On three different occasions six incremental concentrations of BPPA (range: 0.1‐2%; maximum cumulative concentration 4%), timolol (0.1‐1%; 2%), and placebo were administered bilaterally until bronchoconstriction (decrease in FEV1 greater than or equal to 20% and in specific airway conductance (sGaw) greater than or equal to 35% simultaneously) or the maximum cumulative concentration was reached. 3. Airway response was measured as change in FEV1 and sGaw and dose‐response curves to timolol, BPPA and placebo were performed. IOP was measured 3 h after the highest concentration of each study day. 4. Timolol caused dose‐dependent falls in FEV1 and sGaw as well as clinical symptoms of respiratory distress in all subjects. The median cumulative concentrations of timolol required to decrease FEV1 by 20% and sGaw by 35% were 0.98% and 1.53%. Neither placebo (P greater than 0.05) nor BPPA (P greater than 0.05) caused a significant change in sGaw. A fall in FEV1 by 20% not accompanied by a simultaneous fall in sGaw by 35% was found in four subjects following BPPA and in five subjects following placebo.(ABSTRACT TRUNCATED AT 250 WORDS) 1992 The British Pharmacological Society