Calcium Channel Blockers for Treating Angina

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Calcium channel blockers are a large class of drugs used for treating several cardiovascular problems including anginahypertensionsupraventricular tachycardia, and hypertrophic cardiomyopathy.

What Do Calcium Blockers Do?

Calcium channel blockers prevent calcium from entering into the heart muscle cells, and into the smooth muscle cells that cause blood vessels to constrict. By reducing calcium influx, calcium channel blockers cause these muscle cells to "relax." This relaxing effect results in the dilation of blood vessels, and a reduced force of contraction of the heart muscle.

Some calcium channel blockers also slow the sinus node and the rate at which the hear’s electrical impulse transmits through the AV node. These effects make calcium blockers useful in treating some arrhythmias.

What Makes Calcium Blockers Useful In Treating Angina?

All the effects of calcium blockers (blood vessel dilation, reduction in heart muscle contraction, and slower heart rate) reduce the amount of oxygen required by the heart muscle.

Reducing the amount of oxygen used by the heart allows the heart to function longer without developing ischemia, even when blood flow through the coronary arteries is partially blocked by an atherosclerotic plaque. In patients with stable angina, calcium blockers usually increase the amount of exercise that can be performed before angina occurs. Calcium blockers can be especially useful in patients with Prinzmetal's angina (coronary artery spasm) since they can directly prevent spasm of the coronary arteries.

Types Of Calcium Blockers

Several calcium blockers are on the market, and they are not all alike. There are three types of widely used calcium blockers:

1) The dihydropyradines. The drugs nifedipine (Procardia, Adalat), nicardipine (Cardene), felodipine (Plendil), and amlodipine (Norvasc), are called the dihydropyridines.

These drugs cause significant dilation of blood vessels and relatively little effect on the heart muscle and heart rate. They are most useful for treating hypertension.

2) Verapamil. Verapamil (Calan, Covera, Isoptin, Verelan) affects the heart muscle and is particularly effective in slowing the heart rate, but has little effect on blood vessels. It is not very useful for hypertension but is quite good for angina and cardiac arrhythmias.

3) Diltiazem. Diltiazem (Cardizem, Dilacor, Tiazac) has modest effects on both the heart muscle and the blood vessels. It tends to be tolerated better than most other calcium blockers

Using Calcium Blockers for Angina

All the calcium blockers have been used for treating angina. However, the most commonly used calcium blockers are the longer-acting forms of diltiazem and verapamil, amlodipine, or felodipine.

Nifedipine, especially its short-acting forms, should generally be avoided in patients with angina, since the pronounced blood vessel dilation produced by this drug can increase in adrenaline, leading to a more rapid heart rate, and consequently an increase in cardiac oxygen requirements (which can increase the chances of developing cardiac ischemia).

In general, while calcium blockers are useful for relieving angina, they are considered to be inferior to beta blockers. Current recommendations are:

  • Calcium blockers should be tried in patients who cannot tolerate beta blockers.
  • Calcium blockers should be added to beta blockers in patients who have insufficient relief of symptoms with beta blockers.

Other Common Uses of Calcium Blockers

  • Hypertension. The dihydropyradine calcium blockers are quite useful for treating hypertension, and are often used as first line therapy for Stage I hypertension. Read about choosing the “right” drug for hypertension.
  • Supraventricular arrhythmias. Calcium blockers (especially verapamil) partially blocks the function of the AV node, and therefore is often quite useful in treating the supraventricular arrhythmias that rely on the AV node in order to persist. In particular, AV nodal reentrant tachycardia (the most common kind of supraventricular arrhythmia) can often be controlled with verapamil therapy. 
  • Hypertrophic cardiomyopathy. Calcium blockers can be used to help reduce the “stiffness” of the left ventricle in people with hypertrophic cardiomyopathy, and in this way can reduce symptoms.

Side Effects of Calcium Blockers

Common side effects of calcium channel blockers include headache, dizziness, flushing, and foot and ankle swelling. Verapamil, in particular, also tends to cause constipation.

Because calcium blockers tend to reduce the force of contraction of the heart muscle, they should be used with caution (if at all) in patients with heart failure.

It is usually best to avoid verapamil and diltiazem in people with bradycardia since these drugs will further slow the heart rate.


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