The effect on asthma of a new beta blocker, pindolol

Abstract

Pindolol is a recently developed beta-adrenergic antagonist. It possesses intrinsic sympathomimetic activity but is not considered a beta-1-selective agent. Because of the known deleterious effects of beta blockers on bronchial asthma, pindolol was evaluated in a group of asthmatic patients. Fifteen adult atopic asthmatic patients participated in this randomized double-blind study. Six subjects received placebo and nine pindolol with successive weekly doses of 2.5, 5, 10, and 20 mg. Forced expiratory volume in 1 second (FEV 1), vital capacity (VC), maximum midexpiratory flow rate (MMEFR), and quantitative methacholine challenge were performed each week before and 2 hours after drug administration at the time of peak blood level. At the final visit, specific alrway conductance was measured with a body plethysmograph following inhalation of the largest dose of methacholine that did not cause a 20% decrease in FEV 1. The only significant pulmonary function test difference in the two treatment groups was obtained for MMEFR after 5 mg of pindolol. One third of the subjects in both groups demonstrated a 20% or greater decrease in FEV 1 2 hours after the dose sometime during the study. Overall, of the nine subjects on pindolol, six tolerated the final 20 mg dose, and one showed a decrease in FEV 1 at 20 mg, one at 10 mg, and one at 2.5 mg. There were no significant side effects in either group. The only significant methacholine challenge difference in the two groups was observed after the 10 mg dose. Only one patient showed increased sensitivity to methacholine with increasing doses of pindolol. Isoproterenol reversed the methacholine-induced bronchoconstriction, although higher doses were required with the 5 and 10 mg doses of pindolol. No group differences were seen with whole-body plethysmography. Airway conductance changes were not a predictor of subsequent fall in FEF 1. While beta blockers should be used with caution in asthmatic patients, this study suggests that pindolol is generally well tolerated by these patients and can be administered to an asthmatic patient when beta blockade is indicated. The bronchoconstricting effects of pindolol in asthmatic subjects were no greater than those with placebo.