Verapamil

Calcium Channel Blocker (Non-Dihydropyridine)

Generic Name

Verapamil

Drug Class

Non-dihydropyridine calcium channel blocker

Indications

Hypertension
Angina pectoris
Supraventricular tachycardia (SVT)
Atrial fibrillation/flutter (rate control)
Cluster headaches (off-label)

Dosage

Hypertension/Angina: 80–120 mg orally 3 times daily (immediate release) or 180–240 mg/day (extended release)
SVT/Atrial fibrillation: 120–360 mg/day orally (extended release); IV dose for acute conversion: 0.075–0.15 mg/kg over 2 min
Cluster headache prophylaxis (off-label): 240–360 mg/day orally, divided doses or extended release

Note: Adjust dose in hepatic impairment; monitor heart rate and blood pressure.

Route of Administration

Oral (tablet, extended-release) and IV (for acute arrhythmias)

Mechanism of Action

Verapamil inhibits L-type calcium channels in cardiac and vascular smooth muscle. This reduces myocardial contractility, slows AV conduction, and causes vasodilation, lowering blood pressure and controlling heart rate.

Common Adverse Effects

Constipation
Dizziness
Bradycardia
Hypotension
Headache
Peripheral edema

Serious Adverse Effects

Severe bradycardia or AV block
Heart failure exacerbation
Hypotension
Severe constipation leading to obstruction (rare)

Contraindications

Severe hypotension
Second- or third-degree AV block (without pacemaker)
Severe left ventricular dysfunction
Cardiogenic shock
Hypersensitivity to verapamil

Precautions

Monitor heart rate and blood pressure
Use with caution in patients with heart failure or conduction abnormalities
Avoid concomitant use with beta-blockers in patients with conduction disease

Drug Interactions

Beta-blockers – additive bradycardia or AV block
Digoxin – may increase serum digoxin levels
CYP3A4 inhibitors/inducers – alter verapamil plasma levels
Other antihypertensives – additive hypotensive effect

Pregnancy & Lactation

Use with caution during pregnancy and breastfeeding; monitor maternal blood pressure and fetal heart rate.

Patient Counseling

Take at the same time each day
Do not stop therapy abruptly
Monitor heart rate and blood pressure regularly
Report dizziness, fainting, or severe constipation