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Calcium-channel blockers

Published by Bupa's health information team, September 2009.

This factsheet is for people who are taking calcium-channel blockers or who would like information about them.

Calcium-channel blockers work on the muscle cells of the heart and arteries. They are medicines to treat high blood pressure and chest pain (angina). For more information about these conditions, see Related topics.

Why would I take calcium-channel blockers?
What are the main types of calcium-channel blocker?
How do calcium-channel blockers work?
How to take calcium-channel blockers
Special care
Side-effects of calcium-channel blockers
Interactions of calcium-channel blockers with other medicines
Names of common calcium-channel blockers
Questions and answers
Related topics
Further information
Sources

Why would I take calcium-channel blockers?

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

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

One type of calcium-channel blocker (verapamil) is sometimes used to prevent cluster headaches (severe headaches usually affecting the area around one eye or temple).

If you have angina, your doctor will normally only prescribe a calcium-channel blocker if beta-blockers (a different type of heart medicine) didn't work well enough on their own or there is a reason why you can't take them.

What are the main types of calcium-channel blocker?

There are three main types of calcium-channel blockers.

The phenylalkylamines mainly target the heart, reducing how hard it can work. These are used to treat angina, high blood pressure and arrhythmia. These medicines are not suitable for people with heart failure or for people taking beta-blockers, which also block the heart's response to extra work. This group includes verapamil.
The dihydropyridines mainly target the arteries, causing them to become wider and so lowering the blood pressure. This group includes most of the other commonly used calcium-channel blockers, such as amlodipine and nifedipine.
The benzothiazepines target both the heart and the 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?

Heart

Your heart is controlled by special cells that generate electrical impulses, acting like pacemakers. These 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 a 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 the amount of contraction.

Blood vessels

The arteries that carry blood from your heart to the rest of your body 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, the muscle cells in the blood vessels relax, causing the arteries to widen (this is called vasodilation). This helps to lower blood pressure. Calcium-channel blockers also prevent angina by widening the arteries that supply the heart (coronary arteries).

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.

You should make sure that you always have a prescription for the same brand of calcium-channel blocker as different brands can be absorbed into your body slightly differently.

Do not stop taking a calcium-channel blocker suddenly because this may make angina worse. Your doctor will tell you how to reduce your calcium-channel blockers gradually, if you need to stop taking them.

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

Special care

Your doctor may not prescribe calcium-channel blockers if you are pregnant or breastfeeding, if you have recently had a heart attack or have certain other conditions, or if you are taking beta-blockers. Talk to your doctor for more advice.

Side-effects of calcium-channel blockers

This section does not include every possible side-effect of calcium-channel blockers. 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 prevent this, make sure you get up slowly when you stand up from a lying or sitting down position, and stay next to your chair or bed until you're sure that you are not feeling dizzy. You should not drive or do anything else that needs you to be alert until you know how you react to your medicine.

Calcium-channel blockers can also slow your heart down (especially the drugs called verapamil and diltiazem) and cause headaches, constipation, flushing and fluid retention.

Interactions of calcium-channel blockers with other medicines

Check with your doctor or pharmacist before you take any other medicines or herbal remedies at the same time as a calcium-channel blocker.

You should not eat grapefruit or drink grapefruit juice while taking some calcium-channel blockers, as this can affect how this medicine is absorbed by your body. Check with your doctor or your pharmacist.

Names of common calcium-channel blockers

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

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

Generic names	Examples of common brand names
amlodipine	Istin, Exforge (in combination with valsartan)
diltiazem	Tildiem, Adizem-SR, Adizem-XL, Angitil SR, Angitil XL, Calcicard CR, Dilcardia SR, Dilzem SR, Dilzem XL, Slozem, Tildiem LA, Tildiem Retard, Viazem XL, Zemtard
felodipine	Plendil
isradipine	Prescal
lacidipine	Motens
lercanidipine	Zanidip
nicardipine	Nicardipine, Cardene, Cardene SR
nifedipine	Adalat, Adalat LA, Adalat Retard, Adipine MR, Adipine XL, Coracten SR, Coracten XL, Fortipine LA 40, Hypolar Retard 20, Nifedipress MR, Tensipine MR, Valni XL
nimodipine	Nimotop
verapamil	Cordilox, Securon, Half Securon SR, Securon SR, Univer, Verapress MR, Vertab SR 240