Calcium is necessary for the heart to function properly. Special channels allow calcium to flow into heart muscle cells to help it operate. Blood vessel walls also transport calcium, but calcium in these vessels can constrict them, reducing their width. This decreases blood flow to the heart, and can result in chest pain known as angina. Calcium channel blockers alleviate angina by reducing the flow of calcium into blood vessels.
Angina Results from Inadequate Blood Supply to the Heart
Angina is chest pain that occurs when the heart does not receive an adequate supply of blood and oxygen. This can result when excess calcium enters the smooth muscle cells of blood vessels, causing them to constrict, thus decreasing blood flow to the heart. Stable angina occurs when there is a chronic narrowing in a coronary artery that limits blood flow to the heart. In unstable angina, a temporary deficiency of blood supply to the heart muscle occurs suddenly and unpredictably.
Calcium Channel Blockers Increase Blood Flow to the Heart
Calcium channel blockers, or CCBs, are drugs used to treat angina and high blood pressure. LifeHeart.com explains that when calcium ions enter the cells of blood vessels, the vessels contract. CCBs restrict the amount of calcium that enters these cells. By reducing calcium influx into these cells, CCBs cause the cells to relax and allow the blood vessels to dilate, resulting in increased blood flow to the heart. This makes it easier for the heart to pump blood and decreases its need for oxygen, which relieves or prevents angina.
Different CCBs Produce Different Effects
Calcium channel blockers differ in their ability to affect heart rate and contraction and the state of blood vessels. According to Patient UK, the drugs nifedipine (Procardia, Adalat), nicardipine (Cardene), felodipine (Plendil), and amlodipine (Norvasc) cause significant dilation of blood vessels, but have much less effect on the heart muscle and heart rate. Verapamil (Calan, Covera, Isoptin, Veralan) slows heart rate, but has little effect on blood vessels. Diltiazem (Cardizem, Dilacor, Tiazak) has modest effects on both the heart muscle and the blood vessels. In treating angina, the most commonly used CCBs are the longer-acting forms of diltiazem and verapamil, and amlodipine or felodipine.
Side Effects of Calcium Channel Blockers
LifeHeart.com points out that the common side effects of CCBs include headache, dizziness, flushing, and foot and ankle swelling. Like other blood pressure medications, CCBs are associated with sexual dysfunction. The calcium blockers that affect the heart muscle and slow the heart rate should be used with caution, if at all, in patients who have had heart failure or bradycardia, which is a slow heart rate.
Drug Interactions
Most of the interactions between CCBs and other drugs occur with verapamil or diltiazem. These interactions occur because verapamil and diltiazem reduce the elimination of a number of other drugs by the liver. This can lead to toxicity from these drugs. According to pharmacist Dean Elbe, grapefruit juice may elevate blood concentrations of felodipine, verapamil, nisoldipine, nifedipine, and nicardipine, therefore grapefruit juice should not be consumed within twp hours before or four hours after taking these CCBs.
