A rate-limiting calcium-channel blocker
Verapamil
A "rate-limiting" calcium-channel blocker used to lower blood pressure and to slow and steady the heart rate in abnormal heart rhythms.
What is Verapamil?
Verapamil is a calcium-channel blocker that mainly slows the heart and reduces its workload, rather than acting chiefly on blood vessels. It is used for high blood pressure, angina, and certain fast or irregular heart rhythms.
Education and reference only. This is a plain-language guide to Verapamil — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Verapamil is a calcium-channel blocker, but it works differently from the more familiar ones like amlodipine. Amlodipine mainly relaxes blood vessels, whereas verapamil also acts directly on the heart's electrical and pumping system — which is why it is described as "rate-limiting". This makes it useful both for high blood pressure and for slowing a fast or irregular heartbeat, such as atrial fibrillation. It is taken as a long-term tablet (standard and slow-release forms exist). The UK and US brand names overlap (Securon and Cordilox in the UK; Calan and Verelan in the US), but the active ingredient is identical.
How it works
Verapamil blocks calcium channels in the muscle of blood-vessel walls and in the heart. In blood vessels, less calcium entry lets them relax and widen, so blood pressure falls. In the heart, it slows the electrical signals passing through the natural "junction box" (the AV node) between the upper and lower chambers, which steadies and slows a fast heart rate. This dual action on vessels and on the heart's conduction system is what sets it apart from vessel-only calcium-channel blockers like amlodipine.
Company & origin
Originated / developed by: Knoll AG (later acquired by Abbott/BASF).
Verapamil was developed by the German company Knoll AG, having been synthesised in the early 1960s as the first clinically used calcium-channel blocker. It was introduced in the 1960s; Knoll later became part of BASF Pharma and then Abbott.
What it treats
Conditions Verapamil is used for
Practical use
How to take Verapamil
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as prescribed; modified-release forms should be swallowed whole and not crushed or chewed.
- Take it at the same time each day for steady control.
- Expect constipation, which is common, so keep well hydrated and eat plenty of fibre.
- Do not combine it with a beta-blocker without advice, as together they can dangerously slow the heart.
- Report a very slow or irregular heartbeat, marked dizziness or fainting.
Weighing it up
Advantages & disadvantages of Verapamil
Advantages
- Lowers blood pressure and helps control fast or irregular heart rhythms.
- Effective for angina by reducing the heart's workload.
- Does not cause the cough seen with some other heart medicines.
- Available in once-daily modified-release forms.
Disadvantages
- Commonly causes constipation, which can be troublesome.
- Can slow the heart too much, particularly if combined with a beta-blocker.
- May worsen some types of heart failure and is avoided in certain heart conditions.
- Interacts with several medicines, including some statins, increasing their effects.
- Modified-release forms must be swallowed whole and not crushed.
Practical use
Good to know
Constipation is the most common nuisance effect and is worth anticipating with fluids, fibre and activity. Because verapamil slows the heart, it should not be combined with a beta-blocker (such as bisoprolol or atenolol) unless a specialist has advised it, since together they can slow the heart dangerously or cause heart block. Slow-release tablets are usually swallowed whole rather than crushed. It interacts with a long list of medicines, so always have new medicines and supplements checked.
Who should not take it / use with caution
- People with certain slow or blocked heart rhythms (such as significant heart block) or a very slow pulse, unless they have a pacemaker.
- People with heart failure due to a weak pumping action, or very low blood pressure — verapamil can worsen these.
- It should not be combined with a beta-blocker except under specialist advice, because the two together can slow the heart too much.
Monitoring
- Blood pressure and pulse
- Heart rhythm (an ECG) where relevant
- Bowel habit, and for any signs of heart failure
Side effects
- Constipation is the most common and characteristic effect.
- Ankle swelling, flushing, headache, dizziness or tiredness.
- A slow heart rate; rarely, more serious slowing or heart block, or worsening of heart failure — report a very slow pulse, fainting or increasing breathlessness.
Key interactions
- It should not be combined with beta-blockers (such as bisoprolol or atenolol) without specialist advice, as together they can slow the heart dangerously.
- It raises the levels of several statins (such as simvastatin and atorvastatin) and of digoxin, increasing their side-effect risk.
- Care with many other medicines — including some used for blood pressure, certain heart-rhythm drugs, ciclosporin and others; always have new medicines checked.
Available as: Tablets, including standard and slow-release (modified-release) forms. An injection is used in hospital for certain rhythm problems.
Answers
Verapamil: frequently asked questions
Why can't I take verapamil with my beta-blocker?
Both verapamil and beta-blockers slow the heart, so taking them together can slow it too much or cause heart block, which can be dangerous. This combination is only used under specialist supervision. Always tell any prescriber about all your heart medicines, and never add one to the other yourself.
Why does verapamil cause constipation?
Verapamil relaxes muscle, including the muscle in the gut wall, which slows things down and commonly causes constipation. Drinking enough fluid, eating fibre and keeping active all help; if it remains troublesome, your pharmacist or prescriber can advise, as it sometimes leads to a change of medicine.
How is verapamil different from amlodipine?
Both are calcium-channel blockers, but amlodipine mainly relaxes blood vessels, while verapamil also acts on the heart to slow and steady its rate. That extra "rate-limiting" action is why verapamil is also used for heart-rhythm problems — and why it must not be casually combined with a beta-blocker.
Can I crush my slow-release tablets?
Slow-release (modified-release) verapamil tablets are designed to release the medicine gradually and are normally swallowed whole, not crushed or chewed, as crushing can release too much at once. If you have trouble swallowing, ask your pharmacist about a suitable alternative form.
What is the difference between verapamil and brands like Securon or Calan?
They are the same medicine — verapamil is the generic (active-ingredient) name, while Securon and Cordilox are UK brand names and Calan and Verelan are US brand names. Generic verapamil contains the identical active ingredient.
The wider class
About Calcium-channel blockers
Verapamil belongs to the calcium-channel blockers class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF: Verapamil hydrochloride.
- electronic Medicines Compendium (SmPC): Verapamil.
- NICE CKS: Verapamil.
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