Ultra-short-acting beta-blockade: a comparison with conventional beta-blockade.

Esmolol is a beta 1-selective adrenoceptor blocker that is rapidly metabolized by blood and liver esterases. The beta-receptor and hemodynamic effects of esmolol were determined in a group of 12 healthy men and were compared with those induced by both oral and intravenous propranolol. Esmolol was rapidly effective in inducing at least 90% of steady-state beta-blockade within 5 minutes of either initiating or changing the esmolol infusion rate. More importantly, when esmolol infusion was discontinued the beta-blockade had totally disappeared by 18 minutes after esmolol, 300 micrograms/kg/min, and had been reduced by 50% after 750 micrograms/kg/min. In contrast, 30 minutes after discontinuation of a propranolol infusion, there was no change in the level of beta-blockade. Propranolol was much more potent at blocking isoproterenol-induced tachycardia (dose ratio 33.5 +/- 2.5) than was even the highest dose (750 micrograms/kg/min) of esmolol (dose ratio 13.1 +/- 1.0). The same dose of intravenous propranolol was approximately equipotent to oral propranolol, 40 mg every 8 hours (dose ratio 33.5 +/- 2.5 and 34.5 +/- 3.6, respectively). In contrast, propranolol, 40 mg every 8 hours, and esmolol, 300 micrograms/kg/min, were equipotent in antagonizing exercise-induced tachycardia (40.1% +/- 2.3% and 42.7% +/- 3.2%, respectively). Esmolol had striking hypotensive effects. Systolic blood pressure fell by 20 mm Hg during esmolol infusions of 750 micrograms/kg/min. Esmolol appears to be a potent beta 1-selective adrenoceptor antagonist with a particularly strong hypotensive effect. It is likely to be very useful in the treatment of hemodynamically unstable patients and may be useful in the emergency treatment of hypertension.