Some pharmacological aspects of ultra-short acting B-blocker [Esmolol]

ABSTRACT

Some pharmacological actions of esmolol, a new ultrashort acting cardioselective beta adrenergic blocker, were studied on guinea pig's auricles, rabbit's heart, rat's phrenic nerve diaphragm, rabbit's duodenum, rat's uterus as well as dogs blood pressure, ECG pattern and their protective action when administered intravenously before and after induced tachyarrhythmias with adrenaline in pentobarbital anaesthetized dogs was demonstrated. Esmolol induced a marked negative inotropic activity on guinea pig's auricles. On isolated rabbit's heart, the negative inotropic and chronotropic effects were induced by esmolol in concentrations up to 7.5 x10[-7] M/m1. The inhibitory effect of esmolol potency is 1/36.36 as potent of propranolol on rabbit's heart. In anaesthetized dogs. i.v. injection of esmolol at dosage ranged from 7.5 x10[-5] -6X10[-3] M/kg b.wt. produced a significant decrease in systolic and diastolic pressure, while lower doses induced insignificant changes. The electrocardiographic pattern induced by esmolol in dogs were mainly characterized by an increase in the amplitudes of P-wave and T-wave, prolongation of P-R, T-wave, P-wave and P-T intervals. Esmolol in a dose of 6 x 10[-4] M/kg b.wt. produced a good curative effect when injected intravenously after induced arrhythmias with adrenaline than before injection. Esmolol inhibited the indirect muscle twitches of rat's phrenic nerve-diaphragm. Furthermore, esmolol induced a marked inhibition of both amplitudes and frequency of isolated rabbit's duodenum and uterus of rats in concentrations more than 3.86 x 10[-5] and 3.6 x 10[-5] M/m1, respectively