Introduction
Esmolol is a cardioselective beta-1 receptor blocker. It has a rapid onset but short duration of action without causing significant intrinsic sympathomimetic or membrane stabilizing activities at recommended therapeutic doses. It works by blocking beta-adrenergic receptors in the heart, which leads to decreased force and rate of heart contractions. Esmolol prevents the action of two naturally occurring substances: epinephrine and norepinephrine.
Uses
Esmolol is a cardioselective beta-adrenergic blocker used for the short-term control of ventricular rate and heart rate in various types of tachycardia, including perioperative tachycardia and hypertension.
For the rapid control of ventricular rate in patients with atrial fibrillation or atrial flutter in perioperative, postoperative, or other emergent circumstances where short term control of ventricular rate with a short-acting agent is desirable. Also used in noncompensatory sinus tachycardia where the rapid heart rate requires specific intervention.
Associated Conditions
Mechanism of Action
Similar to other beta-blockers, esmolol blocks the agonistic effect of the sympathetic neurotransmitters by competing for receptor binding sites. Because it predominantly blocks the beta-1 receptors in cardiac tissue, it is said to be cardioselective. In general, so-called cardioselective beta-blockers are relatively cardioselective; at lower doses they block beta-1 receptors only but begin to block beta-2 receptors as the dose increases. At therapeutic dosages, esmolol does not have intrinsic sympathomimetic activity (ISA) or membrane-stabilizing (quinidine-like) activity. Antiarrhythmic activity is due to blockade of adrenergic stimulation of cardiac pacemaker potentials. In the Vaughan Williams classification of antiarrhythmics, beta-blockers are considered to be class II agents.
Absorption
Rapidly absorbed, steady-state blood levels for dosages from 50-300 µg/kg/min (0.05-0.3 mg/kg/mm) are obtained within five minutes.
Protein Binding
55% bound to human plasma protein, while the acid metabolite is 10% bound.
Route of Elimination
Consistent with the high rate of blood-based metabolism of esmolol hydrochloride, less than 2% of the drug is excreted unchanged in the urine. The acid metabolite has an elimination half-life of about 3.7 hours and is excreted in the urine with a clearance approximately equivalent to the glomerular filtration rate. Excretion of the acid metabolite is significantly decreased in patients with renal disease, with the elimination half-life increased to about ten-fold that of normals, and plasma levels considerably elevated.
Half Life
Rapid distribution half-life of about 2 minutes and an elimination half-life of about 9 minutes. The acid metabolite has an elimination half-life of about 3.7 hours.
Clearance
- 20 L/kg/hr [Men]
Toxicity
Symptoms of overdose include cardiac arrest, bradycardia, hypotension, electromechanical dissociation and loss of consciousness.
Food Interactions
No interactions found.
Dosage
- Optional loading dose: 500 mcg per kg infused over one minute
- Then 50 mcg per kg per minute for the next 4 minutes
- Adjust dose as needed to a maximum of 200 mcg per kg per minute
- Additional loading doses may be administered
- Loading dose: 500 mcg per kg over 1 minute for gradual control (1 mg per kg over 30 seconds for immediate control).
- Than 50 mcg per kg per minute for gradual control (150 mcg per kg per minute for immediate control) adjusted to a maximum of 200 (tachycardia) or 300 (hypertension) mcg per kg per minute.