Influence of labetalol, propranolol and practolol in patients with asthma

The acute effect of non-selective beta-blockade alone (propranolol) or in combination with alpha-blockade (labetalol) and beta 1-selective blockade (practolol) on the airways was studied in 14 asthmatic patients. Severe bronchoconstriction was not seen in any patient after placebo (saline) or practolol (10 mg i.v.) while pronounced bronchoconstriction was seen in three patients after labetalol (20 mg i.v.) and in six patients after propranolol (5 mg i.v.). The effects of 2 weeks of oral medication with labetalol (200 mg x 2) and placebo were studied in the same patients. Four patients had symptoms of asthma during the labetalol period while none had asthmatic symptoms during the placebo period. The results suggest that coexistent alpha-adrenoceptor blockade fails to prevent asthmatic symptoms caused by beta-blockade.