1. Introduction
Verapamil is a calcium channel blocker (CCB) that works by inhibiting calcium influx in vascular smooth muscle and cardiac cells, leading to vasodilation, reduced heart rate, and decreased myocardial contractility. It is used to treat hypertension, angina, arrhythmias, and migraine prevention.
2. Indications
- Hypertension (High Blood Pressure)
- Angina (Chronic Stable Angina, Vasospastic Angina, Unstable Angina)
- Supraventricular Tachycardia (SVT) / Atrial Fibrillation & Atrial Flutter (Rate Control)
- Migraine Prophylaxis (Off-Label Use)
- Hypertrophic Cardiomyopathy (HCM) (Off-Label Use)
3. Dosage
Adults:
- Hypertension:
- Immediate-Release: 80–120 mg three times daily.
- Extended-Release: 180–240 mg once daily, titrated up to 480 mg/day.
- Angina:
- Immediate-Release: 80–120 mg three times daily.
- Extended-Release: 180–240 mg once daily, max 480 mg/day.
- Supraventricular Tachycardia (SVT) / Atrial Fibrillation (Rate Control):
- IV Dose: 5–10 mg IV over 2 minutes, may repeat after 30 minutes.
- Oral Dose (Maintenance): 120–360 mg/day in divided doses.
- Migraine Prophylaxis (Off-Label):
- 120–240 mg/day, divided into two or three doses.
Paediatric Use:
- SVT: 0.1–0.3 mg/kg IV (max 5 mg/dose) over 2 minutes.
- Hypertension: Rarely used in children, but doses vary based on weight.
Elderly:
- Start at a lower dose (120 mg/day) due to increased sensitivity.
Renal Impairment:
- No major dose adjustment, but monitor for toxicity.
Hepatic Impairment:
- Dose reduction required due to prolonged drug clearance.
- Start with 40 mg three times daily and titrate cautiously.
4. Administration
- Take with food to reduce stomach upset.
- Swallow extended-release tablets whole—do not crush or chew.
- For IV use, administer slowly over 2–3 minutes to prevent hypotension.
5. Forms Available
- Immediate-Release Tablets: 40 mg, 80 mg, 120 mg
- Extended-Release (ER) Tablets: 180 mg, 240 mg, 360 mg
- Injection (IV): 2.5 mg/mL (5 mg/2 mL, 10 mg/4 mL vials)
6. Side Effects
6.1 Common Side Effects:
- Constipation (very common)
- Dizziness
- Low blood pressure (hypotension)
- Fatigue
6.2 Less Common Side Effects:
- Bradycardia (slow heart rate)
- Peripheral oedema (swelling in legs)
- Headache
6.3 Rare but Serious Side Effects:
- Heart Block (AV Block) (especially in patients with pre-existing conduction disorders)
- Severe Hypotension (especially with IV use)
- Worsening Heart Failure (due to negative inotropic effects)
- Liver Dysfunction (Rare cases of hepatotoxicity)
7. Warnings
- Heart Block & Bradycardia: Avoid in patients with 2nd or 3rd-degree AV block without a pacemaker.
- Severe Hypotension: IV verapamil should be given slowly to prevent sudden BP drops.
- Heart Failure Risk: Avoid in patients with severe heart failure or reduced ejection fraction (EF <40%).
- Grapefruit Juice Interaction: Avoid grapefruit juice, as it increases verapamil levels and toxicity risk.
8. Precautions
- Monitor blood pressure and heart rate regularly.
- Caution in liver disease—dose reduction required.
- May cause significant constipation—increase fibre and hydration.
- Use with caution in older adults, who are more sensitive to hypotension.
9. Interactions
- Beta-Blockers (e.g., metoprolol, propranolol): Increased risk of bradycardia and heart block.
- Digoxin: Increases digoxin levels—monitor for digoxin toxicity.
- Statins (e.g., simvastatin, atorvastatin): Increases statin levels, increasing risk of muscle damage (rhabdomyolysis).
- Carbamazepine & Phenytoin: Decreases verapamil effectiveness.
- Grapefruit Juice: Increases verapamil blood levels, leading to toxicity.
10. Monitoring Parameters
- Blood pressure (BP) and heart rate (HR): Every 2–4 weeks initially.
- Electrocardiogram (ECG): Monitor for heart block in high-risk patients.
- Liver function tests (ALT, AST, bilirubin): Especially in long-term users.
- Signs of constipation or fluid retention.
11. Use in Children
- Only used for SVT treatment under specialist guidance.
- Avoid in infants due to risk of severe bradycardia and hypotension.
12. Use in Pregnancy
- Category C:
- Not first-line, but may be used if benefits outweigh risks.
- Safer alternatives (e.g., labetalol, nifedipine) preferred for hypertension.
13. Use in Elderly
- Start at lower doses (e.g., 120 mg/day) to reduce risk of hypotension and bradycardia.
- Monitor for dizziness and fall risk.
14. Use in Kidney Disease
- No major dose adjustment, but monitor for excessive BP drop.
15. Use in Liver Disease
- Dose reduction required—metabolism is slowed in hepatic impairment.
16. Patient Counselling Points
- Take with food to minimise stomach discomfort.
- Do not stop suddenly—taper under medical supervision.
- Avoid grapefruit juice to prevent drug toxicity.
- Monitor blood pressure at home and report very low readings (<90/60 mmHg).
- Report symptoms of slow heart rate (fatigue, dizziness, fainting).
- Increase fibre and fluids to prevent constipation.
17. Table of Brand Names, Manufacturer, and Prices in USD
Brand Name | Manufacturer | Strength/Dosage Form | Price (USD) |
---|---|---|---|
Isoptin | Abbott | 40 mg, 80 mg, 120 mg Tablets | $50 (30 tabs) |
Calan | Pfizer | 80 mg, 120 mg Tablets | $60 (30 tabs) |
Verelan | Lannett | 180 mg, 240 mg ER Capsules | $70 (30 caps) |
Generic Verapamil | Various | 40 mg, 80 mg, 120 mg Tablets | $30 (30 tabs) |
18. 15 FAQs (Frequently Asked Questions)
1. What is Verapamil used for?
It treats hypertension, angina, arrhythmias, and migraine prevention.
2. How does Verapamil work?
It blocks calcium channels, reducing heart rate, blood pressure, and cardiac workload.
3. How long does Verapamil take to work?
Effects start within 1–2 hours, with full effect in 1–2 weeks.
4. Can I stop Verapamil suddenly?
No, sudden stopping can cause rebound hypertension or arrhythmias.
5. Does Verapamil cause weight gain?
No, but fluid retention (swelling) may occur.
6. Can I drink alcohol with Verapamil?
Avoid excessive alcohol—it may worsen dizziness and BP drops.
7. Can Verapamil cause constipation?
Yes, common side effect—increase fibre and fluids.
8. Can I take Verapamil with beta-blockers?
Only under strict monitoring—risk of severe bradycardia.