Usage
- Esmolol is prescribed for the rapid control of ventricular rate in patients with atrial fibrillation or atrial flutter, particularly in perioperative, postoperative, or other emergent situations requiring short-term control. It’s also used for noncompensatory sinus tachycardia when the rapid heart rate necessitates intervention. It’s indicated for supraventricular tachycardia (SVT), and intraoperative and postoperative tachycardia and hypertension. Other uses include hypertensive emergencies, aortic dissection, acute coronary syndrome, thyrotoxicosis, intubation, and refractory ventricular fibrillation/ventricular tachycardia.
- Pharmacological Classification: Esmolol is a cardioselective beta-1 adrenergic receptor blocker (beta blocker).
- Mechanism of Action: Esmolol competitively binds to beta-1 adrenergic receptors in the heart, thereby inhibiting the effects of sympathetic nervous system stimulation. This leads to decreased heart rate, myocardial contractility, and blood pressure.
Alternate Names
- Esmolol hydrochloride.
- Brand Name: Brevibloc.
How It Works
- Pharmacodynamics: Esmolol primarily affects the heart by reducing heart rate, contractility, and conduction velocity. It lowers blood pressure by decreasing cardiac output and, at higher doses (by blocking β2 receptors), can cause bronchoconstriction.
- Pharmacokinetics: Esmolol is administered intravenously. It’s rapidly metabolized by red blood cell esterases to an inactive metabolite, resulting in a short half-life of about 9 minutes. This allows for rapid onset and offset of action. Steady-state plasma concentrations are typically achieved within 5 minutes of continuous infusion.
- Mode of Action: Esmolol competitively binds to beta-1 adrenergic receptors on cardiac myocytes, preventing the binding of endogenous catecholamines like norepinephrine and epinephrine. This inhibits the activation of adenylate cyclase, reduces intracellular cyclic AMP levels, and decreases calcium influx, ultimately leading to reduced heart rate and contractility.
- Receptor Binding, Enzyme Inhibition, or Neurotransmitter Modulation: Esmolol specifically targets beta-1 adrenergic receptors.
- Elimination Pathways: Esmolol is rapidly hydrolyzed by red blood cell esterases to an inactive acid metabolite that is primarily excreted renally.
Dosage
Standard Dosage
Adults:
- Supraventricular Tachycardia (SVT): Loading dose of 500 mcg/kg over 1 minute, followed by a maintenance infusion of 50 mcg/kg/min. Titrate upward in 50 mcg/kg/min increments every 4 minutes as needed to a maximum of 200-300 mcg/kg/min.
- Intraoperative and Postoperative Tachycardia and Hypertension: Two methods:
- Immediate control: 1 mg/kg bolus over 30 seconds, followed by a 150 mcg/kg/min infusion (maximum 300 mcg/kg/min).
- Gradual control: 500 mcg/kg bolus over 1 minute, followed by 50 mcg/kg/min infusion for 4 minutes. If inadequate, repeat loading dose and increase infusion to 100 mcg/kg/min. Titrate further as needed (maximum 300 mcg/kg/min).
- Hypertensive Emergency: 250–500 mcg/kg/min initially, titrated to effect.
Children:
- Safety and efficacy not established; however, off-label use suggests loading doses of 100–500 mcg/kg over 1–2 minutes, followed by maintenance infusions of 25–100 mcg/kg/min, titrated to effect. Maximum infusion rate: 500–1000 mcg/kg/min. Use with caution and consult a pediatric cardiologist.
Special Cases:
- Elderly Patients: Start at the low end of the dosing range due to potential for decreased renal or cardiac function.
- Patients with Renal Impairment: No dosage adjustment is typically required for maintenance infusions up to 150 mcg/kg/min for 4 hours.
- Patients with Hepatic Dysfunction: No dosage adjustment required.
- Patients with Comorbid Conditions: Monitor closely for potential interactions or exacerbations of underlying conditions.
Clinical Use Cases:
- Intubation: 1–2 mg/kg bolus prior to intubation.
- Surgical Procedures: As described above for intraoperative and postoperative tachycardia and hypertension.
- Mechanical Ventilation: Titrate to maintain desired heart rate and blood pressure.
- Intensive Care Unit (ICU) Use: Continuous infusion for hemodynamic control.
- Emergency Situations (e.g., status epilepticus, cardiac arrest): Higher doses may be required, but careful titration is still necessary. Refractory ventricular fibrillation/ventricular tachycardia: 500 mcg/kg bolus, then 50 mcg/kg/min infusion.
Dosage Adjustments:
- Adjust based on patient response, heart rate, and blood pressure.
- Monitor patients with renal impairment closely, especially at higher doses or prolonged infusions.
Side Effects
Common Side Effects:
- Hypotension (symptomatic or asymptomatic).
- Dizziness.
- Diaphoresis (sweating).
Rare but Serious Side Effects:
- Bradycardia.
- Heart block.
- Cardiac failure.
- Bronchospasm.
Long-Term Effects:
- Not typically observed due to short duration of use.
Adverse Drug Reactions (ADR):
- Severe hypotension.
- Heart failure exacerbation.
- Bronchospasm.
Contraindications
- Severe sinus bradycardia.
- Second or third-degree heart block (without a functioning pacemaker).
- Cardiogenic shock.
- Severe hypotension.
- Decompensated heart failure.
- Hypersensitivity to esmolol.
Drug Interactions
- Digoxin.
- Anticholinesterases.
- Antihypertensives (additive effects).
- Sympathomimetics (may reduce esmolol’s effects).
- Calcium channel blockers (may enhance bradycardia or hypotension).
- CYP450 interactions are not clinically significant due to esmolol’s metabolism by red blood cell esterases.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C (Animal studies show some risk, but human studies are limited. Use only if benefits clearly outweigh risks).
- Fetal Risks: Potential for bradycardia and growth restriction in the fetus.
- Breastfeeding: No data available regarding esmolol excretion in breast milk; weigh risks and benefits carefully.
Drug Profile Summary
- Mechanism of Action: Cardioselective beta-1 adrenergic receptor blocker.
- Side Effects: Hypotension, dizziness, diaphoresis; rarely, bradycardia, heart block, cardiac failure.
- Contraindications: Severe bradycardia, heart block, cardiogenic shock, hypotension, hypersensitivity.
- Drug Interactions: Digoxin, anticholinesterases, antihypertensives, sympathomimetics, calcium channel blockers.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: Variable based on indication and patient response (see detailed dosage section above).
- Monitoring Parameters: Heart rate, blood pressure, ECG, respiratory status.
Popular Combinations
- Often used in combination with other antiarrhythmics like amiodarone.
Precautions
- Pre-existing cardiovascular or respiratory conditions.
- Diabetes mellitus.
- Pheochromocytoma.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Esmolol?
A: Dosage varies depending on indication. See the detailed dosage section above for specific recommendations for adults and children.
Q2: How quickly does Esmolol work?
A: Esmolol has a rapid onset of action, typically within minutes of intravenous administration.
Q3: What are the most common side effects of Esmolol?
A: The most common side effects are hypotension, dizziness, and sweating.
Q4: Can Esmolol be used in patients with renal impairment?
A: No dosage adjustment is typically needed for maintenance infusions up to 150 mcg/kg/min for 4 hours; however, close monitoring is advised.
Q5: Is Esmolol safe to use during pregnancy?
A: Esmolol is a Pregnancy Category C drug. Use with caution and only if the benefits clearly outweigh the risks.
Q6: What drugs interact with Esmolol?
A: Esmolol interacts with digoxin, anticholinesterases, other antihypertensives, sympathomimetics, and calcium channel blockers.
Q7: How is Esmolol administered?
A: Esmolol is administered intravenously, either as a bolus or continuous infusion.
Q8: How long can a patient be on an Esmolol infusion?
A: Maintenance infusions can be continued for up to 48 hours.
Q9: What is the mechanism by which Esmolol decreases heart rate?
A: Esmolol competitively binds to beta-1 adrenergic receptors in the heart, preventing the binding of sympathetic neurotransmitters. This leads to reduced heart rate and contractility.
A: Esmolol is rapidly metabolized by hydrolysis by esterases in red blood cells.
