Calcium channel blocker is a drug used to treat certain disorders of the heart and blood vessels. Calcium channel blockers, also called calcium antagonists, include diltiazem, sold under such trade names as Cardizem and Dilacor; and nifedipine, often sold under the trade names Procardia and Adalat. These drugs stop calcium from entering muscle cells in the heart and blood vessels. Blocking the entry of calcium interferes with muscle cell contraction. As a result, blood vessels expand and carry more blood and oxygen to tissues.
These drugs are used to prevent severe chest pains called angina pectoris that are caused by lack of oxygen in the heart. These pains occur when arteries in the heart become narrowed due to fatty deposits, abnormal contractions, or a combination of these conditions. Narrowed vessels cannot supply the heart with enough oxygen during exercise, stress, or other periods of hard work. Calcium channel blockers expand the heart’s arteries and restore its supply of oxygen.
Calcium channel blockers also reduce blood pressure by expanding blood vessels throughout the body. This drop in pressure lessens the heart’s workload and reduces its need for oxygen.
Some calcium channel blockers, called short-acting forms, act quickly. Other types, called long-acting or extended-release forms, act more slowly. Studies show that the different forms vary in their safety and effectiveness in treating certain disorders. For example, several studies suggest that treating high blood pressure with short-acting nifedipine raises the risk of heart attack or death. The increased risk may occur because this drug lowers blood pressure too rapidly.
