Verapamil

Generic Name: Verapamil

Brand Names: Calan, Verelan, Isoptin

Verapamil is a calcium channel blocker used to treat high blood pressure, angina, and irregular heart rhythms. It also helps prevent migraine headaches.

CardiovascularCalcium Channel BlockersHypertensionAntiarrhythmics

Drug Class

Calcium Channel Blocker (non-dihydropyridine / phenylalkylamine)

Pregnancy

Category C (crosses the placenta; use only if clearly needed)

Available Forms

Immediate-release tablets (40 mg, 80 mg, 120 mg), Sustained-release tablets (120 mg, 180 mg, 240 mg), Extended-release capsules (100 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg, 360 mg), Intravenous injection (2.5 mg/mL)

What It's Used For

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Condition	Starting Dose	Maintenance Dose
Hypertension (SR/ER)	180 mg once daily (ER) or 80 mg three times daily (IR)	180–480 mg/day in 1–2 divided doses
Angina pectoris (IR)	80–120 mg three times daily	240–480 mg/day in 3–4 divided doses
Supraventricular tachycardia (IV)	2.5–5 mg IV bolus over 2 minutes	May repeat 5–10 mg after 15–30 minutes if needed; max 20 mg total
Atrial fibrillation/flutter (rate control)	240–320 mg/day in 3–4 divided doses (IR)	Titrate to heart rate control; individualized

Side Effects

Common Side Effects:

Constipation (very common)
Dizziness
Headache
Peripheral edema
Nausea
Fatigue
Bradycardia

Serious Side Effects:

Severe hypotension
Heart failure exacerbation
High-degree AV block
Asystole (with IV use)
Hepatotoxicity (rare)

Drug Interactions

Beta-blockers (metoprolol, atenolol): Additive negative effects on heart rate, AV conduction, and cardiac contractility; IV combination is contraindicated; oral use requires extreme caution.
Digoxin: Verapamil increases digoxin serum concentrations by 50–75%; reduce digoxin dose and monitor levels closely.
Simvastatin/Lovastatin: Verapamil inhibits CYP3A4 and increases statin levels; simvastatin dose should not exceed 10 mg/day when combined with verapamil.
Lithium: Verapamil can alter lithium levels unpredictably (both increases and decreases reported) and may increase neurotoxicity risk.
Dantrolene: IV verapamil with IV dantrolene can cause hyperkalemia and cardiovascular collapse; avoid combination.
Grapefruit juice: Inhibits CYP3A4 in the gut, increasing verapamil bioavailability and risk of hypotension and bradycardia.

Additional Information

Verapamil is a non-dihydropyridine calcium channel blocker used to treat hypertension, angina, and supraventricular arrhythmias. It has significant effects on both cardiac and vascular smooth muscle.

Mechanism of Action

Verapamil blocks L-type calcium channels:

Cardiac effects: Reduces heart rate (negative chronotropy), slows AV conduction (negative dromotropy), and decreases contractility (negative inotropy)
Vascular effects: Relaxes vascular smooth muscle, causing vasodilation
Coronary vasodilation: Increases coronary blood flow and oxygen delivery
Decreased cardiac workload: Reduces afterload and myocardial oxygen demand
AV nodal blockade: Slows conduction, useful for rate control in atrial fibrillation

Available Formulations

Immediate-release tablets: 40 mg, 80 mg, 120 mg
Extended-release tablets/capsules: 100 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg, 360 mg
Injectable: 2.5 mg/mL

Medical Uses

FDA-Approved Indications:

Hypertension
Angina (chronic stable, vasospastic/Prinzmetal's, unstable)
Supraventricular tachyarrhythmias (PSVT, atrial fibrillation/flutter rate control)
Hypertrophic cardiomyopathy (symptom relief)

Dosing Guidelines

Hypertension (Extended-Release):

Initial: 180-240 mg once daily (or 120 mg at bedtime)
Maximum: 480 mg daily

Angina (Immediate-Release):

Initial: 80-120 mg three times daily
Maximum: 480 mg daily

Atrial Fibrillation/Flutter Rate Control:

IV: 5-10 mg (0.075-0.15 mg/kg) over 2 minutes; may repeat 10 mg after 30 minutes
Oral: 240-480 mg daily in divided doses

PSVT (IV):

5-10 mg IV over 2 minutes; may repeat 10 mg after 15-30 minutes

Important Safety Information

Contraindications:

Severe left ventricular dysfunction
Hypotension (SBP <90 mmHg)
Cardiogenic shock
Sick sinus syndrome (without pacemaker)
Second or third degree AV block (without pacemaker)
Atrial fibrillation/flutter with accessory pathway (WPW syndrome)
Concurrent IV beta-blocker administration

Warnings and Precautions:

Heart failure: May worsen; use with caution if LVEF reduced
Hepatic impairment: Reduced clearance; lower doses needed
Renal impairment: May require dose adjustment
Conduction abnormalities: May worsen AV block
Hypertrophic cardiomyopathy with outflow obstruction: Use with caution

Drug Interactions

Beta-blockers: Additive negative inotropic and chronotropic effects; avoid IV combination
Digoxin: Verapamil increases digoxin levels 50-75%; monitor levels
CYP3A4 substrates (simvastatin, atorvastatin): Verapamil increases statin levels; use lower statin doses
Lithium: May reduce lithium levels; neurotoxicity possible
Carbamazepine, phenytoin, cyclosporine, tacrolimus: Verapamil increases their levels
Rifampin: Dramatically reduces verapamil levels

Special Populations

Hepatic Impairment: Reduce dose; use 30% of normal dose in cirrhosis
Renal Impairment: Monitor closely; may need reduced dose
Elderly: Start with lower doses; increased sensitivity
Pregnancy: Category C; use only if benefit outweighs risk
Lactation: Present in milk; generally compatible with breastfeeding
Pediatric: Safety and efficacy established for SVT; dose by weight

Frequently Asked Questions

Grapefruit and grapefruit juice inhibit the CYP3A4 enzyme that metabolizes verapamil, which can raise drug levels significantly. Avoid grapefruit products while on verapamil to prevent excessive blood pressure lowering and slow heart rate.

Both are calcium channel blockers, but verapamil (non-dihydropyridine) primarily affects the heart — slowing heart rate and AV conduction — while amlodipine (dihydropyridine) primarily dilates blood vessels. Verapamil is preferred for arrhythmias while amlodipine is more commonly used for hypertension alone.

Do not stop verapamil abruptly, as this can lead to rebound angina or hypertension. Your doctor will gradually taper the dose when discontinuing the medication.

Yes. Constipation is one of the most common side effects of verapamil, affecting up to 12% of patients. Increasing fiber intake, staying hydrated, and using stool softeners if needed can help manage this side effect.

Yes, off-label. Verapamil is one of the first-line preventive treatments for cluster headaches and is also used off-label for migraine prevention, particularly at doses of 240–480 mg/day. ECG monitoring is recommended at higher doses.

Questions to Ask Your Doctor

Consider discussing these topics at your next appointment:

✓Which formulation of verapamil (immediate-release vs. extended-release) is best for my condition?
✓Do I need regular ECG monitoring while on verapamil?
✓Are any of my current medications unsafe to combine with verapamil?
✓What heart rate should I monitor for that would indicate I need to contact you?

Schedule an Appointment

Related Health Conditions

This medication is commonly used to treat or manage the following conditions:

Atrial Fibrillation

Atrial fibrillation, a common arrhythmia characterized by rapid, irregular heartbeats, increases risk of stroke and heart failure, often linked to age, hypertension, and heart disease.

Learn More

Migraine

Migraine is a debilitating neurological condition causing recurrent headaches with throbbing pain, nausea, and light/sound sensitivity, likely stemming from complex brain, nerve, and blood vessel interactions.

Learn More

Portal Hypertension

Portal hypertension, an elevated pressure in the portal vein due to blockage often from cirrhosis or other pre-hepatic causes, can lead to serious complications like bleeding and ascites.

Learn More

Secondary Pulmonary Hypertension

Secondary pulmonary hypertension, unlike its primary form, arises from underlying conditions such as heart/lung disease, blood clots, or connective tissue disorders, increasing lung artery pressure.

Learn More

Supraventricular Tachycardia

Supraventricular Tachycardia (SVT) is a rapid heart rhythm originating above the ventricles, often caused by re-entry circuits, leading to palpitations and dizziness, significantly impacting quality of life.

Learn More

Vertigo

Vertigo, a spinning sensation distinct from dizziness, often stems from inner ear or brain issues like BPPV or Meniere's, sometimes triggered by head trauma or medication.

Learn More

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.