| Abstract: | Esmolol is a new ultra-short-acting beta-adrenergic receptor blocking agent that may be useful in the treatment of patients with heart disease. We gave esmolol as an intravenous bolus injection (over 30 seconds) to 12 healthy men in a dose-ranging study; each subject received two doses. Our dosing schedule began with 30 mg in the first subject and ended with 100 mg and 150 mg in the final four subjects. We measured blood esmolol concentration, PR interval, QRS duration, QTc interval, cardiac cycle, systolic blood pressure, and diastolic blood pressure. Esmolol doses of 150 mg produced blood esmolol concentrations of 0.868 to 1.47 micrograms/ml. The peak PR interval recorded after esmolol was significantly longer than the control PR interval in four subjects who received 100 and 150 mg doses (192 +/- 7.9 msec vs. 177 +/- 10.6 msec; P = 0.00002). Peak prolongation of the PR interval was recorded 6 to 10 minutes after the bolus, at which time blood esmolol concentrations were negligible. Esmolol did not consistently affect any other pharmacodynamic variable. Giving esmolol as an intravenous bolus injection may be a simple alternative to loading and maintenance infusion in some clinical settings. |
