ACTIONS AND PHARMACOLOGY This is an ultra-short-acting b1-selective adrenergic blocker, which has rapid distribution and elimination half-lives of 2 and 9 min, respectively. When given as an intravenous bolus, followed by an infusion, 90 percent of b blockade is achieved within 5 min; however, when given as an infusion without a bolus, steady-state blood levels are reached within 30 min. Within 2 min of discontinuing an infusion, there is a significant decrease in the b-antagonist activity, and, generally, all blockade will resolve within 30 min. Because of its rapid onset of action, short duration of action, and easy reversibility—properties not found in other b blockers—esmolol is very useful in acute settings.18 When compared with sodium nitroprusside, esmolol provides similar rapid control of hypertension without producing the excessive reduction in DBP and reflex tachycardia that are seen with sodium nitroprusside.
INDICATIONS Esmolol has been used in the treatment of supraventricular tachycardias; to lower pulse and blood pressure in perioperative patients and in patients with myocardial infarction, unstable angina, and thyrotoxicosis; and to blunt rises in blood pressure associated with intubation. It has also been used for severe hypertension but is not particularly efficacious as monotherapy.
USE A loading dose of 0.5 (mg/kg)/min may be given over 1 min prior to the initiation of an infusion of 0.05 to 0.3 (mg/kg)/min. Esmolol may also be given without a loading dose but then takes longer to reach a steady state. It is usually used in combination with other agents such as nitroprusside or phentolamine for hypertensive emergencies.
SIDE EFFECTS AND CONTRAINDICATIONS Because of its b-antagonist activity, the use of esmolol should be avoided in patients with asthma or COPD. It also should not be used to treat patients with cocaine-induced cardiovascular complications, because of the predominant b blockade, leaving relatively unblocked a receptors.
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