Esmolol

Esmolol is a short-acting, selective beta-1 adrenergic receptor antagonist used primarily for acute control of heart rate and blood pressure. Its rapid onset and short half-life make it ideal for critical care and perioperative settings.

Uses

1. Supraventricular Tachycardia (SVT): Acute control of heart rate in SVT, atrial fibrillation, or atrial flutter.
2. Intraoperative Hypertension and Tachycardia: Perioperative management of acute tachycardia and hypertension.
3. Thyroid Storm: Management of tachycardia and hypertension associated with hyperthyroidism.
4. Aortic Dissection: Reduces heart rate and blood pressure to decrease stress on the aortic wall.
5. Acute Myocardial Ischemia/Unstable Angina: Reduces myocardial oxygen demand by controlling heart rate and blood pressure.
6. Postoperative Hypertension: Used for managing acute postoperative hypertension, particularly after cardiac surgeries.

Dosage and Administration

• Supraventricular Tachycardia & Hypertension:
  • IV Bolus: 0.5 mg/kg over 1 minute.
  • Continuous Infusion: 50-200 mcg/kg/min (max 300 mcg/kg/min). Adjust every 4-5 minutes as needed.
• Pediatric Dose:
  • Bolus: 0.1-0.5 mg/kg followed by 50-300 mcg/kg/min infusion.

Dose Adjustment in Different Diseases

• Renal Impairment: No dose adjustment required as Esmolol is metabolized by plasma esterases.
• Hepatic Impairment: No dose adjustment required.
• Heart Failure: Use with caution due to potential for worsening heart failure.
• Elderly: Start with lower doses and titrate carefully.

Presentation/Form

• IV Solution: 10 mg/mL in 10 mL vials or premixed infusion bags.

Pharmacokinetics

• Absorption: Administered intravenously, rapid onset.
• Onset of Action: 1-2 minutes.
• Peak Plasma Concentration: Achieved within minutes.
• Duration: Approximately 9-10 minutes.
• Metabolism: Rapidly metabolized by plasma esterases.
• Elimination Half-Life: Approximately 9 minutes.
• Excretion: Metabolites primarily excreted in urine.

Pharmacodynamics

Esmolol competitively blocks beta-1 adrenergic receptors, leading to decreased heart rate, myocardial contractility, and cardiac output. It has minimal effects on beta-2 receptors at therapeutic doses.

Drug Interactions

1. Calcium Channel Blockers: Increased risk of bradycardia and hypotension.
2. Other Beta-Blockers: Increased risk of severe bradycardia.
3. Digoxin: Elevated risk of AV block.
4. Insulin and Oral Antidiabetics: May mask hypoglycemic symptoms.
5. Anesthetic Agents: Enhanced hypotensive effects.

Comparison with Other Drugs in the Same Category

• Metoprolol: Longer duration of action, oral and IV forms available.
• Propranolol: Non-selective beta-blocker, crosses the blood-brain barrier, longer duration.
• Labetalol: Combined alpha and beta-blockade, useful for hypertensive crises.
• Atenolol: Longer half-life, suitable for chronic management.

Precautions and Special Considerations

1. Heart Failure: Monitor closely; Esmolol may worsen symptoms.
2. Bronchospastic Disease: Avoid or use with extreme caution.
3. Diabetes Mellitus: Monitor blood glucose closely.
4. Peripheral Vascular Disease: Use cautiously to avoid exacerbation of symptoms.
5. Pregnancy: Category C; weigh benefits versus risks.
6. Withdrawal: Taper gradually to avoid rebound tachycardia or hypertension.

Side Effects

• Common: Hypotension, bradycardia, dizziness, nausea.
• Serious: AV block, heart failure, bronchospasm (especially in patients with reactive airway disease), profound hypotension.

Recent Updates and Guidelines

• 2023 ACC/AHA Guidelines: Esmolol remains a first-line agent for acute management of perioperative hypertension and SVT.
• European Society of Cardiology (ESC) Guidelines: Recommends Esmolol for rate control in critically ill patients where rapid titration is essential.
• Thyroid Storm Management: Esmolol is emphasized as a first-choice beta-blocker due to its rapid onset and titratability.

Facts to Remember

1. Esmolol has a rapid onset (1-2 minutes) and short duration (9-10 minutes).
2. Metabolized by plasma esterases; no dose adjustment needed for hepatic or renal impairment.
3. Ideal for situations requiring rapid and precise control of heart rate and blood pressure.
4. Requires continuous IV infusion for sustained effect.
5. Monitor for bradycardia and hypotension during infusion.

References

1. NCBI StatPearls - Esmolol: https://www.ncbi.nlm.nih.gov/books/NBK518965/
2. Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 13th edition
3. Stoelting’s Pharmacology and Physiology in Anesthetic Practice, 5th edition
4. 2023 ACC/AHA Guidelines for the Management of Hypertension
5. European Society of Cardiology (ESC) Guidelines for Perioperative Care