Calcium-channel blockers
- Madeeha Waheed, Pharmaceutical Policy Manager at Bupa
Calcium-channel blockers are medicines for your heart and circulation. They act on the cells of your heart and blood vessels (arteries). 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 condition that affects blood supply to fingers and toes in cold temperatures or when you’re stressed)
- cluster headaches (severe headaches affecting the area around one eye or temple)
These medicines aren’t suitable for everyone. Tell your doctor about any other health conditions you have and medicines you take. For more information about this, see our section on interactions.
Let your doctor know if you’re pregnant, breastfeeding, or trying for a baby. If you are, you can’t take some types of calcium-channel blocker, and others may cause problems.
It’s your decision whether to take a medicine or not. Discuss your options with your doctor and ask them about the benefits and drawbacks of any medicines they suggest.
How calcium-channel blockers work
Calcium plays a key role in how muscles work. As muscles contract, calcium flows into the muscle cells through special channels. Muscles in your heart and arteries need a steady flow of calcium to contract and pump blood round your body. Calcium is also necessary for regulating your heartbeat.
Effect on the heart
Calcium-channel blockers slow the flow of calcium into your heart muscle cells. This reduces how fast and strongly your heart pumps.
These medicines also act on the cells conducting the electrical flow in your heart. This affects the speed of your heartbeat. So calcium-channel blockers can help with symptoms of angina and irregular heart rhythms.
Effect on blood vessels
Calcium-channel blockers also slow the flow of calcium into muscle cells in your blood vessels. These cells then relax, causing the arteries to widen (vasodilation). This helps to lower your blood pressure.
By widening the coronary arteries that supply your heart, these medicines help to prevent angina. This allows more oxygen to reach the heart muscle cells.
Types of calcium-channel blocker
There are two main groups of calcium-channel blocker.
Dihydropyridine calcium-channel blockers widen your arteries. Examples include amlodipine (such as Istin), felodipine (such as Cardioplen XL and Felotens XL) and nifedipine (such as Adipine XL and Nifedipress MR). You may have any of these for Raynaud’s phenomenon, angina, or high blood pressure.
Non-dihydropyridines, or ‘rate-limiting’ calcium-channel blockers widen your arteries and slow your heart. Examples include diltiazem ( Dilzem SR and Zemtard) and verapamil (Securon SR and Vertab SR). These medicines reduce the load on your heart as well as how fast it beats. Your doctor may prescribe them for angina, high blood pressure, or arrhythmia.
Your doctor will offer you the calcium-channel blocker that’s most suitable for you. This depends on
- the health condition you have
- your general health
- other medicines that you take.
Some calcium-channel blockers come in long-acting ('modified release') versions. Letters such as SR, XL, LA, or MR in the name means your tablet slowly releases the active ingredient over time. For more information on this, see our FAQ about these letters.
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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. If you forget to take a tablet, check your medicine’s patient information leaflet. This explains what 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 them, it can raise your blood pressure. This can 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 your doctor or pharmacist’s instructions about taking 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.
Seek immediate advice from your pharmacist, doctor, or the hospital if:- you take too much medicine
- you think you’re reacting badly to your medicine
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
- the herbal remedy St John’s Wort can decrease the effects of some calcium-channel blockers
- alcohol and calcium-channel blockers both lower blood pressure, so taking both can cause problems
Check your medicine’s patient information leaflet for any foods or drinks to avoid. If you have any queries, ask your pharmacist.
Calcium-channel blockers may interact with other medicines. This includes some other heart medicines and some antibiotics. If you’re taking beta-blockers, you won’t be able to take certain calcium-channel blockers.
If you’re taking a calcium-channel blocker, always check with your pharmacist or doctor before taking any other medicines. This includes over-the-counter medicines and herbal remedies.
Side-effects of calcium-channel blockers
You may not have side-effects with a calcium-channel blocker. But, as with all medicines, it’s possible to have one or more side-effects. With calcium-channel blockers, side-effects vary depending on which type you take. Check your medicine’s patient information leaflet. It will list possible side-effects and say how common they are.
The most common side-effects of calcium-channel blockers include:
- flushing
- headache
- swelling in your feet and ankles
- dizziness
- rapid or irregular heartbeat (palpitations)
- nausea (feeling sick or being sick)
- rashes
Some calcium-channel blockers, especially verapamil, may cause constipation. This is because they can affect the muscle in the walls of your bowel. This can slow down movement in your bowel, leading 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
Bupa's medicines checklist (PDF, 0.8MB), helps you understand what to check for before taking a medicine.
Calcium-channel blockers are medicines for your heart and arteries (blood vessels). They’re only available on prescription, usually as tablets. You may have them to treat a number of different health conditions, including angina and high blood pressure.
For more information, see our section on uses of calcium-channel blockers.
Calcium-channel blockers affect the heart and blood vessels. There are a variety of reasons why your doctor may suggest them – for example, to treat angina or high blood pressure. There are two different types of calcium-channel blocker. Your doctor will choose the one that is most suitable for you.
For more information, see our sections on uses of calcium-channel blockers and types of calcium-channel blocker.Letters such as SR, XL, LA, or MR in the name means your tablet is ‘slow release’. This means it releases your medicine slowly and steadily over a long period of time. Doctors often call these ‘modified release’ medicines. You must swallow this type of calcium-channel blocker whole. Don’t chew or crush them up because their slow-release mechanism will no longer work.
Calcium-channel blockers aren’t suitable for everyone. Let your doctor know if you’re pregnant, breastfeeding, or trying for a baby because you shouldn’t take some calcium-channel blockers, and others may cause problems. You should also let your doctor know if you have any other health conditions and take medicines for them.
For more information, see our sections on uses of calcium-channel blockers and interactions of calcium-channel blockers.
Which is best will depend on your individual circumstances. For example, one calcium-channel blocker may be a good choice for high blood pressure. But if you also have angina, you may need a different calcium-channel blocker that can treat both. It may also depend on any other health conditions you have or medicines you take. Your doctor will explain the best choice for you.
For more information, see our section on types of calcium-channel blocker.
Angina
Angina is when you have chest pain or an uncomfortable tight feeling in your chest.
High blood pressure (hypertension)
Heart attack
Coronary heart disease
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- Liz Woolf, Freelance Health Editor
