Osmotic release oral drug delivery system of metoprolol in hypertensive asthmatic patients. Pharmacodynamic effects on beta 2-adrenergic receptors.

This study investigated the effects of an osmotic release oral drug delivery system of metoprolol on the changes induced by cumulative doses of inhaled salbutamol on bronchomotor tone, skeletal muscle, and the circulatory system after single (day 1) and multiple (day 7) dosing in 18 hypertensive asthmatic patients (forced expiratory volume in 1 second > 50% predicted; diastolic blood pressure > 90 mm Hg). The patients were given 14/190 mg metoprolol, 100 mg atenolol, and placebo once daily for a 7-day period each in a randomized, double-blind, crossover design. At the estimated time of peak plasma concentrations, cumulative doses of salbutamol (12.5, 37.5, 112.5, 412.5, 812.5, and 1612.5 micrograms) were applied every 20 minutes. Specific airway conductance, finger tremor amplitude, heart rate, and blood pressure were registered at baseline and at each dose increment. The slopes of the salbutamol dose-response curves of specific airway conductance did not differ on day 1 (P > .05). On day 7, atenolol caused a shift of the dose-response curves of specific airway conductance to the right (P < .05), whereas metoprolol was indistinguishable from placebo (P > .05). The median cumulative salbutamol concentrations causing a 50% increase in specific airway conductance were 416 and 384 micrograms (days 1 and 7, respectively) for placebo, 594 and 444 micrograms for metoprolol, and 562 and 1419 micrograms for atenolol. The median cumulative salbutamol concentrations causing a 35% increase in tremor were 732 and 706 micrograms for placebo, 812 and 1213 micrograms for metoprolol, and 797 and 1323 micrograms for atenolol.(ABSTRACT TRUNCATED AT 250 WORDS)