Verapamil — NZ Medication Guide

What is Verapamil?

Verapamil (generic name: verapamil hydrochloride) is a medication used primarily for hypertension, angina, and supraventricular arrhythmias including atrial fibrillation. Verapamil tablets and modified-release preparations are funded by Pharmac on the Pharmaceutical Schedule without Special Authority.

In New Zealand, verapamil is used primarily for rate control in atrial fibrillation and SVT management, as well as for angina. BPAC NZ advises particular caution with the verapamil-beta-blocker combination due to high risk of serious cardiac conduction problems — this combination should generally be avoided. Verapamil should not be used in patients with heart failure and reduced ejection fraction (HFrEF) as it can worsen cardiac function.

What is Verapamil Used For?

Verapamil is prescribed by healthcare professionals in New Zealand for the following indications:

• Supraventricular tachycardia (SVT) — rate control and conversion
• Atrial fibrillation and atrial flutter — ventricular rate control
• Hypertension (chronic management)
• Chronic stable angina and variant angina
• Hypertrophic cardiomyopathy (symptom relief)

How Does Verapamil Work?

Verapamil is a non-dihydropyridine calcium channel blocker that acts on both vascular smooth muscle and cardiac tissue. It blocks L-type calcium channels in the heart, slowing conduction through the atrioventricular (AV) node and reducing heart rate. This makes it effective for controlling fast heart rhythms. It also causes vasodilation, reducing blood pressure and relieving angina.

How to Take Verapamil

Take verapamil exactly as prescribed — dosing frequency depends on whether it is immediate-release (2–3 times daily) or modified-release (once or twice daily). Always swallow modified-release tablets whole. Take with food to reduce gastrointestinal effects. Do not stop suddenly — discuss with your doctor before discontinuing. Grapefruit juice should be avoided as it can increase verapamil levels.

Common Side Effects

Like all medications, Verapamil may cause side effects. Common side effects include:

• Constipation (very common)
• Dizziness and lightheadedness
• Nausea
• Headache
• Flushing
• Ankle swelling (less common than with dihydropyridines)

Serious Side Effects — Seek Medical Attention

Contact your doctor or call 111 immediately if you experience any of the following serious effects:

• Bradycardia (abnormally slow heart rate) — dizziness, fainting
• Heart block (AV conduction delay)
• Hypotension — especially in combination with other cardiac medications
• Heart failure exacerbation in patients with reduced ejection fraction
• Liver toxicity (rare)

Drug Interactions

Always inform your prescriber and pharmacist of all medications, supplements, and herbal products you are taking. Notable interactions with Verapamil include:

• Beta-blockers — CONTRAINDICATED in combination (IV); oral combination requires specialist supervision — risk of heart block and cardiac arrest
• Digoxin — verapamil significantly increases digoxin levels; dose reduction required
• Simvastatin — verapamil increases statin levels; limit simvastatin dose to 20mg
• Colchicine — verapamil increases colchicine levels; risk of toxicity
• Grapefruit juice — increases verapamil blood levels
• CYP3A4 inhibitors — increase verapamil exposure

New Zealand Prescribing Information

In New Zealand, verapamil is used primarily for rate control in atrial fibrillation and SVT management, as well as for angina. BPAC NZ advises particular caution with the verapamil-beta-blocker combination due to high risk of serious cardiac conduction problems — this combination should generally be avoided. Verapamil should not be used in patients with heart failure and reduced ejection fraction (HFrEF) as it can worsen cardiac function.

Frequently Asked Questions

Can I take verapamil with my beta-blocker?

This combination is generally not recommended without specialist supervision. Both verapamil and beta-blockers slow the electrical conduction system of the heart. Together, they can cause dangerously slow heart rates, heart block, or even cardiac arrest. Always inform your cardiologist or doctor if you are on both types of medication.

Why does verapamil cause constipation?

Calcium channels are also present in the smooth muscle of the gastrointestinal tract. By blocking these channels, verapamil slows bowel movement, leading to constipation — the most common side effect. Staying well-hydrated, eating a fibre-rich diet, and regular physical activity can help manage this. If constipation is severe, a stool softener may be recommended by your pharmacist.

References & Further Information

The following New Zealand and international resources were used to inform this page:

• New Zealand Formulary — Verapamil
• Pharmac — Funded Medicines Schedule
• BPAC NZ — Atrial Fibrillation Management
• Medsafe — Verapamil Data Sheet

Reviewed by a Registered Pharmacist — KiwiMeds New Zealand