Esmolol (trade name Brevibloc) is a cardioselective beta1 receptor blocker with rapid onset, a very short duration of action, and no significant intrinsic sympathomimetic or membrane stabilising activity at therapeutic dosages.
Esmolol decreases the force and rate of heart contractions by blocking beta-adrenergic receptors of the sympathetic nervous system, which are found in the heart and other organs of the body. Esmolol prevents the action of two naturally occurring substances: epinephrine and norepinephrine.
Indication
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.
Toxicity
Symptoms of overdose include cardiac arrest, bradycardia, hypotension, electromechanical dissociation and loss of consciousness.
Affected Organisms
Humans and other mammals
Biotransformation
Rapidly metabolized by hydrolysis of the ester linkage, chiefly by the esterases in the cytosol of red blood cells and not by plasma cholinesterases or red cell membrane acetylcholinesterase. Mainly in red blood cells to a free acid metabolite (with 1/1500 the activity of esmolol) and methanol.
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.
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.
Protein Binding
55% bound to human plasma protein, while the acid metabolite is 10% bound.
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.
A methyl ester that is methyl 3-(4-hydroxyphenyl)propanoate in which the hydrogen attached to the phenolic hydroxy group is substituted by a 2-hydroxy-3-(isopropylamino)propyl group.
