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Calcium Channel Blockers

What are calcium channel blockers?

Calcium channel blockers are medicines that help relax blood vessels. Relaxing the blood vessels lowers the blood pressure. Blood can flow more easily, and the heart doesn't have to work as hard to pump blood.


There are several different calcium channel blockers. Amlodipine, diltiazem, felodipine, isradipine, nicardipine, nifedipine, nisoldipine, and verapamil are generic names for common calcium channel blockers. Which medicine is best for you depends on your condition and health.

How do they work?

Calcium channel blockers slow the movement of calcium from the blood into the muscle cells of the blood vessels and heart. Muscle cells need calcium to be able to squeeze (contract). Getting less calcium relaxes the blood vessels. They open up and blood flows more easily through them. This helps lower blood pressure and the heart doesn't have to work as hard. Muscle cells in other parts of the body store their own calcium and don't depend on getting calcium from the blood.

When are they used?

Calcium channel blockers are used to treat:

  • high blood pressure (hypertension)
  • angina (chest pain caused by blockage of an artery in the heart)
  • some abnormal heart rhythms
  • Raynaud's phenomenon (a blood vessel problem in the hands or feet)
  • coronary artery disease (CAD).

Calcium channel blockers may also be used to prevent migraine headaches.


They may be used alone or with other medicines.

What should I watch out for while taking this medicine?

Some calcium channel blockers may make angina worse. Angina is a feeling of tightness, squeezing, or pain in the chest. It happens when the heart does not get enough oxygen-rich blood. Calcium channel blockers may also cause the heart to beat too slowly. Talk with your healthcare provider about this.


Calcium channel blockers can slightly reduce the heart's pumping ability. For most people, the good effect of lowering blood pressure outweighs this bad effect. For some people, however, the reduced pumping of the heart causes heart failure. Heart failure means that the heart is not pumping well enough to keep fluid from building up in the body. Some symptoms of heart failure are tiredness, swelling of the legs and ankles, unexplained coughing or wheezing, and trouble breathing.


Your healthcare provider will check your blood pressure and heart rate regularly while you are taking this medicine.


Don't eat grapefruit or drink grapefruit juice while taking a calcium channel blocker. Grapefruit affects the way this medicine works and may increase the risk of side effects.


Other medicines that you may be taking can increase or decrease the effect of calcium channel blockers. Be sure to tell all healthcare providers who treat you about all of the products you are taking.


If you are taking a calcium channel blocker, call your healthcare provider right away if:

  • You notice that you are having more trouble breathing.
  • You have swelling in your legs, feet, or ankles.
  • You have severe dizziness or fainting.
  • You have a fast, irregular, or slow heartbeat.

Other possible side effects include:

  • constipation
  • headache
  • rash
  • dizziness (especially when you stand up quickly)
  • drowsiness
  • flushing
  • nausea
  • gum swelling or tenderness.

Not all calcium channel blockers have the same side effects. If you have new symptoms while taking this medicine, tell your healthcare provider right away. Don't suddenly stop taking this medicine unless your provider approves. Some problems can get worse if you suddenly stop taking this medicine.


Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.


HIA File drug4258.htm Release 13/2010

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