Systemic haemodynamic and beta-adrenoceptor antagonistic effects of bisoprolol in conscious pigs: a comparison with propranolol.

We studied the cardiovascular profile of the new cardioselective beta-adrenoceptor antagonist bisoprolol in the conscious pig and compared this profile with that of propranolol. Acute i.v. administration of bisoprolol (16-1024 micrograms.kg-1) did not affect mean arterial blood pressure but caused dose-related decreases in cardiac output (from 8 to 17%; p less than 0.05) due to a negative chronotropic action (heart rate reduction ranging from 9 to 21%; p less than 0.05) as stroke volume was unaffected. Max LVdP/dt decreased (ranging from 18 to 27%; p less than 0.05) while left ventricular end-diastolic blood pressure (from 8.6 +/- 0.6 to 15 +/- 0.2 mmHg; p less than 0.05) and systemic vascular resistance (from 8 to 18%; p less than 0.05) increased. Propranolol in a dose-range from 25-300 micrograms.kg-1 produced strikingly similar changes. Bisoprolol was more effective in antagonizing the isoproterenol-induced responses of max LVdP/dt than those on either heart rate or diastolic arterial blood pressure, whereas propranolol caused equi-effective inhibitions of the responses of heart rate and max LVdP/dt. However, with propranolol also the inhibition of the diastolic arterial blood pressure was less marked than for the other parameters. Propranolol proved to be the more potent beta-adrenoceptor antagonist, as the isoproterenol dose ratios of all 3 parameters during beta-adrenoceptors blockade with propranolol exceeded those obtained with bisoprolol.