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Calcium-channel blockers

Key points

  • Calcium-channel blockers treat angina, high blood pressure (hypertension), disturbance of normal heart rhythm (arrhythmia) and Raynaud's phenomenon (pale, cold hands and feet).
  • They work by reducing the contraction of the heart muscle and/or muscles in the walls of arteries. Different calcium-channel blockers have different effects.

Calcium-channel blockers work on the muscle cells of the heart and the arteries. These medicines are used to treat chest pain (angina) and high blood pressure (hypertension).

Why would I take calcium-channel blockers?

Your GP may prescribe calcium-channel blockers if you have:

  • angina
  • high blood pressure
  • disturbance of the normal heart rhythm (arrhythmia)
  • Raynaud's phenomenon (pale, cold hands and feet caused by narrowing of the arteries that supply them with blood)

If you get cluster headaches you may be prescribed a particular type of calcium-channel blocker called verapamil to try to prevent them. Cluster headaches are severe headaches usually affecting the area around one eye or temple.

What are the main types of calcium-channel blocker?

There are three main types of calcium-channel blockers.

  • The phenylalkylamines mainly affect your heart, reducing how hard it can work. You may be prescribed these to treat angina, high blood pressure and arrhythmia. These medicines aren’t suitable if you have heart failure or if you’re taking beta-blockers. This group includes verapamil.
  • The dihydropyridines mainly affect your arteries, causing them to become wider, which lowers blood pressure. They are used to treat Raynaud’s phenomonen. This group includes most of the other commonly used calcium-channel blockers, such as amlodipine and nifedipine.
  • The benzothiazepines affect both your heart and your arteries. These can be used to treat angina or high blood pressure. This group includes diltiazem.

Individual calcium-channel blockers work in different ways, so one that is taken to treat a certain condition may not be suitable for another.

How do calcium-channel blockers work?

Effect on the heart

Your heartbeat is controlled by special cells that generate electrical impulses, acting like pacemakers to regulate how often your heart beats. These electrical impulses flow from cell to cell within the heart and are converted into chemical signals.

One of these chemical signals is a rising level of calcium inside the muscle cell. This causes the muscle to contract.

Calcium-channel blockers slow down the amount of calcium that can get into heart muscle cells and so reduce how fast and strongly it can contract. This effect can help with the symptoms of angina and irregular heart rhythms.

Effect on blood vessels

Arteries carry blood from your heart to the rest of your body. They have walls that contain a special type of muscle called smooth muscle which controls the width of the arteries.

As the level of calcium inside muscle cells increases, the muscle contracts and the artery narrows. This raises your blood pressure because your blood is squeezed into a smaller space.

When calcium channels are blocked, calcium can’t enter the cells so there is no signal to contract. Instead, the muscle cells in the blood vessels relax, causing the arteries to widen (this is called vasodilation). This helps to lower your blood pressure. Calcium-channel blockers also prevent angina by widening the coronary arteries that supply your heart. This allows more oxygen to reach the heart muscle cells.

How to take calcium-channel blockers

Calcium-channel blockers are only available on prescription. They usually come as tablets or capsules that you take once or twice a day. Long-acting versions, which are sometimes called 'modified release', are also available.

It’s important that you always have a prescription for the same brand of calcium-channel blocker. This is because different brands aren’t necessarily absorbed by your body in the same way.

Don’t stop taking a calcium-channel blocker suddenly because this may make angina worse. Your GP will tell you how to reduce your calcium-channel blockers gradually if you need to stop taking them.

Always ask your GP for advice and read the patient information leaflet that comes with your medicine.

Special care

Your GP may not prescribe calcium-channel blockers if you’ve recently had a heart attack or taking beta-blockers. Or, if you’re pregnant or breastfeeding. Talk to your GP for more advice.

Side-effects of calcium-channel blockers

Side-effects are the unwanted effects of taking a medicine. This section doesn’t include every possible side-effect of calcium-channel blockers. Please read the patient information leaflet that comes with your medicine for more information.

Calcium-channel blockers can cause a drop in your blood pressure. This can make you feel dizzy when you stand up. To help prevent this, make sure you get up slowly when you stand up from lying or sitting down. Also stay next to your bed or chair until you're sure that you aren’t feeling dizzy. Don’t drive or do anything else that needs you to be alert until you know how you react to your medicine.

Calcium-channel blockers can slow down your heart (especially verapamil) and can cause headaches, constipation, flushing of your face and fluid retention, especially around your ankles.

Other possible side-effects include:

  • feeling sick
  • palpitations
  • tiredness
  • dizziness
  • rashes

Interactions of calcium-channel blockers with other medicines

Some calcium-channel blockers can be affected if you eat grapefruit or drink grapefruit juice. This can cause the medicine to be absorbed by your body at a different rate. Check with your pharmacist to see if you can still have grapefruit with your calcium-channel blocker.

Calcium-channel blockers can also interact with other medicines, including some other heart medicines and certain antibiotics. Always check with your GP or pharmacist before you take any other medicines or herbal remedies at the same time as a calcium-channel blocker.

Names of common calcium-channel blockers

The main types of calcium-channel blockers are shown in the table below.

All medicines have a generic name. Many medicines also have one or more brand names. Generic names are written in lower case, brand names start with a capital letter.

Generic names Examples of common brand names
amlodipine Exforge (in combination with valsartan), Istin
diltiazem Adizem-SR, Adizem-XL, Angitil SR, Angitil XL, Calcicard CR, Dilcardia SR, Dilzem SR, Dilzem XL, Slozem, Tildiem, Tildiem LA, Tildiem Retard, Viazem XL, Zemtard
felodipine Cardioplen XL, Felogen XL, Felotens XL, Keloc SR, Neofel X, Parmid XL, Plendil, Triapin (in combination with ramipril), Vascalpha
isradipine

Prescal

lacidipine Motens
lercanidipine

Zanidip

nicardipine Cardene, Cardene SR
nifedipine Adalat, Adalat LA, Adalat Retard, Adipine MR, Adipine XL, Beta-Adalat (in combination with atenolol), Coracten SR, Coracten XL, Fortipine LA 40, Nifedipress MR, Tenif (in combination with atenolol), Tensipine MR, Valni XL
nimodipine Nimotop
verapamil Cordilox, Securon, Half Securon SR, Securon SR, Univer, Verapress MR, Vertab SR 240

 

Reviewed by Dylan Merkett, Bupa Health Information Team, November 2013.

Find out more about our health editors

For answers to frequently asked questions about calcium channel blockers, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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