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Calcium Channel Blockers

E.g. Verapamil, diltiazem, amlodipine and nifedipine.

What Calcium Channel Blockers Do?

How do I take them?

Side effects

What Do Calcium Channel Blockers do?

Calcium Channel blockers are prescribed to lower blood pressure, prevent angina (chest pain) or control certain abnormal heart rhythms.

There are two types of calcium channel blocker:

1. Verapamil and diltiazem. These drugs act mainly by lowering your heart rate and making the contractions of the heart less strong. This reduces the workload of the heart and therefore lowers blood pressure and prevents angina (chest pain).    

Verapamil should not be used with a beta blocker, as beta blockers also slow the heart rate and the combined effect can potentially slow the heart rate too much.

2. The second type includes nifedipine, amlodipine and felodipine. These drugs lower blood pressure and prevent angina by relaxing and widening the blood vessels. This allows blood to flow more easily and increases the supply of blood and oxygen to the heart.

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How do I take them?

  • Calcium channel blockers should be swallowed whole with a glass of water. It is important not to crush or chew the tablets or capsules. They are formulated to release the drug slowly to maintain steady levels of the drug in your body. Crushing or chewing the tablets or capsules can interfere with the slow release of the drug. It is also important to stay on the same brand of diltiazem or verapamil since different ones release the medicine at different rates.

  • Calcium channel blockers should be taken at the same time each day. It is better to take them before or during a meal.

  • If you are taking a calcium channel blocker you should avoid grapefruit juice as it can increase the levels of drug in your body and increase the risk of side effects.

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Side effects

Calcium channel blockers don't usually cause problems but can occasionally cause flushing of the face, headache and dizziness.  They can also cause ankle swelling particularly if you sit down for a long time.  Frequent walks and raising your feet on a footstool may help to reduce the swelling (water tablets will not reduce the swelling). Verapamil can cause constipation which may require treatment with a laxative.

If you think you have any side effects from this medicine be sure to mention them to your GP, practice nurse or pharmacist.

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