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Calcium-channel blockersThis factsheet is for people who would like information about taking calcium-channel blockers. 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, please see the separate BUPA health factsheets High blood pressure and Angina.
Why would I take them?Your doctor may prescribe you with calcium-channel blockers if you have:
If you have angina, your doctor will normally only prescribe a calcium-channel blocker if beta-blockers (a different family of heart drugs) didn't work well enough on their own or were not suitable for you. What are the main types?The two main types of calcium-channel blockers are as follows.
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?Your heart is controlled by special cells that act like pacemakers and generate electrical impulses. These impulses flow from cell to cell within the heart and are converted into chemical signals that cause the muscles to tense and squeeze (contract). 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 a cell and so reduce the amount of contraction. 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 the muscle cell goes up, the muscle contracts and the artery narrows. This raises the blood pressure because the same amount of blood is squeezed into a smaller space. Blocking calcium channels relaxes the muscle cells in the blood vessels and so widens the arteries (this is called vasodilation) and helps lower blood pressure. Calcium-channel blockers also prevent angina by widening the arteries that supply the heart (coronary arteries). How to take a calcium-channel blockerCalcium-channel blockers are only available on prescription. They usually come as tablets 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, as this may make symptoms of angina worse. This type of medicine needs to be reduced slowly, and on the advice of your doctor. Always read the patient information leaflet that comes with your medicine. Side-effectsCalcium-channel blockers can cause a big drop in your blood pressure. This can cause you to feel dizzy when you stand up. So, after taking a dose, you need to get up slowly from lying or sitting down and stay next to your chair or bed until you are sure that you are not feeling too dizzy. You should not drive (or do anything that needs you to be alert) until you know how you react to the medicine. Calcium-channel blockers can also slow the heart down (especially the drugs called verapamil and diltiazem) and cause headaches, constipation, flushing and fluid retention. Interactions with other medicinesCheck 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 a calcium-channel blocker, as this may affect how this medicine is absorbed by your body. Names of common calcium-channel blockersExamples of common calcium-channel blockers are shown in the table. The generic name is the chemical name of a medicine. If a manufacturer has rights over a medicinal compound, it is given a brand name. Often there is more than one brand name associated with a generic name. Generic names are normally written with a lower-case initial letter and brand names normally start with an upper-case letter.
Further information
Sources
Published by BUPA's health information team, healthinfo@bupa.com, February 2007.
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