What is verapamil used for?

Uses of Verapamil in Clinical Practice

Verapamil is primarily used for treating supraventricular tachycardias (SVTs), hypertension, and certain types of headaches, with its mechanism of action being calcium channel blockade that affects cardiac conduction and vascular tone. 1, 2

Cardiovascular Applications

Supraventricular Tachycardias

• First-line treatment for narrow-complex reentry SVTs when vagal maneuvers and adenosine fail 1
• Effective for:
  • Atrioventricular nodal reentrant tachycardia (AVNRT)
  • Multifocal atrial tachycardia (MAT) - both acute treatment and ongoing management 1
  • Rate control in atrial fibrillation/flutter 1

Dosing for SVT:

• IV administration: 2.5-5 mg bolus over 2 minutes (3 minutes in older patients)
• Can repeat with 5-10 mg every 15-30 minutes to maximum 20-30 mg 1
• Oral verapamil for ongoing management of recurrent SVTs 1

Hypertension

• FDA-approved for treatment of hypertension 2
• Reduces cardiovascular events, primarily strokes and myocardial infarctions
• Often used as part of comprehensive cardiovascular risk management

Non-Cardiovascular Uses

Cluster Headache

• Used at higher doses (360-720 mg daily) for prophylactic treatment of cluster headaches
• Requires approximately double the dose used for cardiovascular conditions due to limited blood-brain barrier penetration 3

Mechanism of Action

• Primary mechanism: Blocks L-type calcium channels, reducing calcium influx into cardiac and vascular smooth muscle cells 4, 5
• Effects:
  • Slows conduction through AV node
  • Causes peripheral and coronary vasodilation
  • Has negative inotropic effects on cardiac contractility
  • Also blocks other calcium channels (T-, P-, N-, and Q-type) 3

Important Contraindications and Precautions

Absolute Contraindications

• Wide-complex tachycardias of unknown origin 1, 6, 7
• Pre-excited atrial fibrillation/flutter (Wolff-Parkinson-White syndrome) 1, 6
• Impaired ventricular function or heart failure 1, 6
• Concurrent use with beta-blockers (risk of profound bradycardia) 1

Cautions

• Hypotension (major potential side effect) 1
• Sinus node dysfunction or severe conduction abnormalities 1
• Asthma 1
• Hepatic dysfunction (affects drug metabolism) 5

Clinical Pearls

• Verapamil can be dangerous in ventricular tachycardia - one study showed 59% of patients experienced serious adverse effects when verapamil was incorrectly given for VT 7
• For patients with hypocalcemia requiring verapamil, consider administering calcium chloride or calcium gluconate 5 minutes before verapamil 6
• Potential interaction with digoxin by impairing its renal excretion 5
• In pregnancy, verapamil may be considered for SVT when adenosine and beta-blockers are ineffective or contraindicated 1

Algorithm for Verapamil Use in SVT

1. Confirm narrow-complex tachycardia (avoid in wide-complex tachycardias)
2. Try vagal maneuvers and/or adenosine first
3. If unsuccessful and patient is hemodynamically stable:
   • Administer verapamil 2.5-5 mg IV over 2-3 minutes
   • Monitor for hypotension and bradycardia
4. If no response after 15 minutes, can give additional 5-10 mg doses
5. For long-term management, consider oral verapamil

Remember that verapamil should never be given to patients with suspected ventricular tachycardia as it can precipitate ventricular fibrillation and cause severe hemodynamic compromise 6, 7.