Cardiohemodynamic effects of bopindolol in normotensive conscious dogs. A comparative study with pindolol

Cardiohemodynamic effects and the beta-blocking action of a new beta-adrenoceptor blocking agent, bopindolol (Sandonorm) were compared with those of pindolol in conscious unrestrained dogs. The intravenous injection of pindolol (3-100 micrograms/kg) increased the heart rate and decreased the total peripheral resistance dose-dependently and markedly, while the same doses of bopindolol had no effect on the heart rate and decreased the total peripheral resistance only at the maximum dose (100 micrograms/kg). These changes were antagonized by propranolol (3 mg/kg). Isoprenaline (isoproterenol, 0.1 microgram/kg)-induced tachycardia was inhibited dose-dependently by both beta-blockers to similar degrees. While the decrease in the total peripheral resistance by isoprenaline was inhibited by pindolol dose-dependently, the inhibition by lower doses of bopindolol was not so marked; the inhibition became greater as the doses of bopindolol were increased. These results indicate that bopindolol is a beta 1-selective beta-blocker with an affinity to this subtype of the beta-adrenoceptor comparable to that of pindolol. Unlike pindolol, it exerted no partial agonist activity at the beta-adrenoceptor. Instead it produced the partial agonist activity at the beta 2-adrenoceptor at the highest dose tested.