Ultra-short-acting beta-blockade: A comparison with conventional beta-blockade

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Abstract
Esmolol is a β1‐selective adrenoceptor blocker that is rapidly metabolized by blood and liver esterases. The β‐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 β‐blockade within 5 minutes of either initiating or changing the esmolol infusion rate. More importantly, when esmolol infusion was discontinued the β‐blockade had totally disappeared by 18 minutes after esmolol, 300 µg/kg/min, and had been reduced by 50% after 750 µg/kg/min. In contrast, 30 minutes after discontinuation of a propranolol infusion, there was no change in the level of β‐blockade. Propranolol was much more potent at blocking isoproterenol‐induced tachycardia (dose ratio 33.5 ± 2.5) than was even the highest dose (750 µg/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 µg/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 µg/kg/min. Esmolol appears to be a potent β1‐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. Clinical Pharmacology and Therapeutics (1985) 38, 579–585; doi:10.1038/clpt.1985.227

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