Calcium-channel Blockers

Calcium-channel blockers are medicines that work on the cells of your heart and arteries (blood vessels). They can treat a number of different health conditions. 

Uses of calcium-channel blockers

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

• angina
• high blood pressure
• a disturbance of your normal heart rhythm (arrhythmia)
• Raynaud's phenomenon (a health condition that affects your blood vessels in cold temperatures or when you’re stressed)
• cluster headaches (severe headaches that usually affect the area around one eye or temple) 

These medicines aren’t suitable for everyone. If you’re pregnant or breastfeeding, you shouldn’t take some types of calcium-channel blockers, and others may cause problems. So, let your doctor know if you’re pregnant, breastfeeding or trying for a baby. Tell them if you have any other health conditions and about any medicines you take too. See Interactions below for more about this.

It’s your decision whether to take a medicine or not. Discuss your options with your doctor and ask them about the pros and cons of any medicines they suggest.

How calcium-channel blockers work

Calcium plays a key role in how the muscles in your heart and arteries contract to pump blood round your body. To do this, calcium flows into these cells through holes, or channels.

Effect on the heart

Calcium-channel blockers slow down the amount of calcium that can get into your heart muscle cells. This reduces how fast and strongly your heart can contract (pump). The medicines also act on cells that conduct the electrical flow in your heart and this affects the speed of this electrical flow through your heart. These effects can help with the symptoms of angina and irregular heart rhythms.

Effect on blood vessels

Calcium-channel blockers restrict how much calcium can enter the muscle cells in your blood vessels. These then 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.

Types of calcium-channel blockers

There are two main groups of calcium-channel blocker.

• Dihydropyridine calcium-channel blockers widen your arteries. Examples include amlodipine, felodipine (eg Cardioplen XL and Felotens XL) and nifedipine (eg Adipine XL and Nifedipress MR). Dihydropyridines may be used to treat Raynaud’s phenomenon, angina and high blood pressure.

• Non-dihydropyridines, or ‘rate-limiting’ calcium-channel blockers widen your arteries and affect your heart. Examples include diltiazem (eg Dilzem SR and Zemtard) and verapamil (eg Securon SR and Vertab SR). These reduce how hard it has to work and how fast it beats. Your doctor may prescribe these medicines to treat angina, high blood pressure and arrhythmia.

Your doctor will offer you the calcium-channel blocker that’s most suitable for you. This will depend on what health condition you have, as well as your general health and other medicines that you take. 

Taking calcium-channel blockers

Calcium-channel blockers are only available on prescription, usually as tablets. The information that comes with your medicine will tell you how to take it, and how often. Some calcium-channel blockers come in long-acting ('modified release') versions.

If you forget to take a tablet, check the patient information leaflet that comes with your medicine. This will explain what you need to do if you miss a dose.

Don’t stop taking your calcium-channel blockers unless your doctor tells you to. If you suddenly stop taking calcium-channel blockers, it can raise your blood pressure and cause pain and tightness in your chest (angina). If you’d like to stop taking your medicine, your doctor will tell you how to do this safely.

Always follow the instructions your doctor or pharmacist gives you about when to take your medicines. Read the patient information leaflet that comes with your medicine carefully. If you have any questions about your medicines or how to take them, ask your pharmacist.

If you take too much medicine, or think you’re reacting badly to it, seek advice from a health professional immediately. This could be from your pharmacist, doctor or the hospital.

Interactions of calcium-channel blockers

Calcium-channel blockers may interact with some foods and medicines. For instance:

• grapefruit juice can increase the effects of some calcium-channel blockers, which can cause problems
• alcohol and calcium-channel blockers can both cause low blood pressure, so together might cause problems

Check the information that comes with your medicine to see if there are any recommendations about foods and drinks to avoid. And if you have any queries, ask your pharmacist.

Calcium-channel blockers may interact with other medicines, including some other heart medicines and some antibiotics. If you’re taking beta-blockers, you won’t be able to take certain calcium-channel blockers. Always check with your pharmacist or doctor before you take any other medicines or herbal remedies at the same time as a calcium-channel blocker.

Side-effects of calcium-channel blockers

You may not get any calcium-channel blocker side-effects but, as with all medicines, there’s  a possibility. Side-effects vary, according to which calcium-channel blocker you take. The patient information leaflet can tell you exactly which side-effects may happen and how common they are with your particular medicine. Some of the most common side-effects of calcium-channel blockers include:

• flushing (where your skin suddenly turns red)
• headache
• swollen feet and ankles
• dizziness
• rapid or irregular heart beat (palpitations)
• nausea (feeling sick or being sick)
• tummy pain
• a skin rash

Some calcium-channel blockers, especially verapamil, may cause constipation. This is because calcium-channel blockers have an effect on the muscle that forms part of the walls of your bowel. This can slow down movements in your bowel and lead to constipation.

Side-effects may settle down on their own, so give your new medicine a chance and wait a few days to see if things get better. If the side-effects continue and you feel unwell, contact your doctor. Don’t stop taking the medicine without discussing it with your GP first. 

Medicines checklist

Our handy medicines checklist helps you see what to check for before taking a medicine.