A group of drugs used to treat several disorders of the heart and circulation
Calcium channel blocker drugs may be prescribed to treat angina, a disabling chest pain that occurs when too little oxygen reaches the heart muscle. These drugs may also be used in the treatment of high blood pressure (see Hypertension). The calcium channel blocker verapamil is used to treat some abnormal heart rhythms (see Arrhythmias). Nifedipine may be used to treat Raynaud’s phenomenon, a disorder in which spasm of arteries in the hands or feet restricts the blood supply to the fingers or toes. Verapamil may be taken regularly to reduce the frequency of cluster headaches, in which blood vessels in the head may constrict and then widen, causing severe headache.
How do they work?
Muscle cells need calcium to contract. Calcium channel blockers reduce the amount of calcium entering the muscle cells in blood vessel walls. This action causes the muscle cells to relax and the blood vessels to widen, thereby reducing blood pressure. This widening of blood vessels is thought to be the reason why calcium channel blockers work in the treatment of Raynaud’s phenomenon and in the prevention of cluster headaches. Since the drugs reduce the amount of calcium that enters heart muscle cells, they reduce both the force and the rate of the heartbeat and therefore help to relieve angina.
Verapamil also slows down the flow of electrical impulses through the heart and thus slows the heartbeat. It may be used in treating some arrhythmias in which the heart beats excessively fast.
How are they used?
Calcium channel blockers may be used alone or in combination with other drugs that are used in the treatment of angina, hypertension, or certain types of arrhythmia. Usually, the drugs are initially prescribed at a low dose, and the dose is gradually increased to an effective level. The ideal dose for you will be one that is high enough to allow the drug to be effective without causing troublesome side effects.
What are the side effects?
The most common side effects of calcium channel blockers are headache, light-headedness, flushing, and swollen ankles. Constipation can sometimes be a problem, particularly if you are taking verapamil. If you are constipated, you may find it helpful to eat more dietary fibre and drink plenty of fluids. Grapefruit may increase the effects of some of these drugs and should be avoided. Occasionally, taking calcium channel blockers can cause nausea, palpitations, excessive tiredness, and rashes. Some calcium channel blockers may not be suitable for people with heart failure because they may make the symptoms worse.
Do not suddenly stop taking a calcium channel blocker drug without first consulting your doctor. Abrupt withdrawal could cause worsening of your angina.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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