Verapamil hydrochloride

How it works

It blocks L-type calcium channels in cardiac and vascular smooth muscle, slowing atrioventricular nodal conduction and reducing heart rate, myocardial contractility and vascular tone.

Prescribing in practice

• Verapamil is strongly negatively inotropic and chronotropic, so combining it with a beta-blocker risks severe bradycardia, heart block or hypotension, and this combination should generally be avoided.
• It is contraindicated in significant left ventricular dysfunction or heart failure, high-grade AV block and certain accessory-pathway arrhythmias, and it should be avoided in ventricular tachycardia.
• It inhibits CYP3A4 and raises levels of several drugs (including some statins and digoxin), and commonly causes constipation.

Monitoring

Monitor heart rate, blood pressure and the ECG (especially AV conduction) when initiating or adjusting therapy, and review for heart-failure symptoms.

Counselling the patient

• Report marked dizziness, fainting, very slow pulse or swelling ankles.
• Manage constipation with diet and fluids and seek advice if troublesome.
• Tell prescribers you take verapamil before starting new medicines, as interactions are common.

Evidence & guidelines

Verapamil's role in rate control and angina is well established, and NICE recommends rate-limiting calcium-channel blockers among options for rate control in atrial fibrillation when beta-blockers are unsuitable.