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What are calcium channel blockers and how do they work?

In order to pump blood, the heart needs oxygen. The harder the heart works, the more oxygen it requires. Angina (heart pain) occurs when the supply of oxygen to the heart is inadequate for the amount of work the heart must do. By dilating the arteries, CCBs reduce the pressure in the arteries. This makes it easier for the heart to pump blood, and, as a result, the heart needs less oxygen. By reducing the heart's need for oxygen, CCBs relieve or prevent angina. CCBs also are used for treating high blood pressurebecause of their blood pressure-lowering effects. CCBs also slow the rate at which the heart beats and are therefore used for treating certain types ofabnormally rapid heart rhythms.

For what conditions are calcium channel blockers used?

CCBs are used for treating high blood pressure, angina, and abnormal heart rhythms (for example, atrial fibrillation, paroxysmal supraventricular tachycardia).

They also may be used after a heart attack, particularly among patients who cannot tolerate beta-blocking drugs, have atrial fibrillation, or require treatment for their angina.

Unlike beta blockers, CCBs have not been shown to reduce mortality or additional heart attacks after a heart attack.

CCBs are as effective as ACE inhibitors in reducing blood pressure, but they may not be as effective as ACE inhibitors in preventing the kidney failurecaused by high blood pressure or diabetes.

They also are used for treating:

• pulmonary hypertension, 
  
  
• Raynaud's syndrome, 
  
  
• cardiomyopathy, and
  
  
• subarachnoid hemorrhage.

CCBs are also used in the prevention of migraine headaches.

Are there any differences among calcium channel blockers?

CCBs differ in their duration of action, the process by which they are eliminated from the body, and, most importantly, in their ability to affect heart rate and contraction. Some CCBs [for example, amlodipine (Norvasc)] have very little effect on heart rate and contraction so they are safer to use in individuals who have heart failure or bradycardia (a slow heart rate). Verapamil (Calan, Isoptin) and diltiazem (Cardizem) have the greatest effects on the heart and reduce the strength and rate of contraction. Therefore, they are used in reducing heart rate when the heart is beating too fast.

What are the side effects of calcium channel blockers?

• The most common side effects of CCBs are constipation, nausea,headache, rash, edema (swelling of the legs with fluid), low blood pressure, drowsiness, and dizziness. 
  
  
• Liver dysfunction and over growth of gums may also occur. When diltiazem (Cardizem) or verapamil (Calan, Isoptin) are given to individuals with heart failure, symptoms of heart failure may worsen because these drugs reduce the ability of the heart to pump blood. 
  
  
• Like other blood pressure medications, CCBs are associated with sexual dysfunction.