Features November 2009 Issue

What You Need to Know About CCBs

Calcium channel blockers reduce the effect of calcium on the heart and arteries.

Calcium channel blockers (CCBs) are used to treat heart disease, angina (chest pain), heart arrhythmias, and cardiomyopathy. They also may be used to treat high blood pressure in individuals with angina and/or a high risk of stroke, and alongside other drugs to treat resistant high blood pressure.

CCBs increase the supply of blood and oxygen to the heart by relaxing blood vessels. They achieve this effect by attaching to the surface membrane of the muscles in the arteries, slowing the rate at which calcium passes into the heart muscle and into the blood vessel walls, which, in turn, decreases the contraction of both. The effect is to slow the rate at which the heart beats, reducing its workload and treating any arrhythmia, and also to increase the diameter of the arteries so that blood pressure falls—this also relieves pressure on the heart, by making it easier to pump blood.

CCBs differ in their effect on the heart rate—for example, amlodipine (Norvasc) has minimal effect on heart rate, so it may be used to treat individuals with heart failure or bradycardia (slow heart rate). Others, such as verapamil (Isoptin) and diltiazem (Cardizem) are more likely to be used if it is necessary to lower the heart rate.

Possible Side Effects

CCBs can cause a range of side effects that may differ depending on which medication is prescribed. Side effects include nausea, fatigue, swelling of the abdomen, ankles and/or feet, skin flushing, heartburn, constipation (particularly with verapamil), dizziness or lightheadedness and headaches. If you experience any of these reactions, contact your doctor.

Important Precautions

Several different types of medication can either boost or reduce the effects of CCBs, so it is important that you inform your doctor about any other prescription or over-the-counter drugs you take.

CCBs may interact with other drugs used to treat high blood pressure, particularly beta blockers such as acebutolol (Sectral), atenolol (Tenormin) and metoprolol (Lopressor), and ACE inhibitors such as benazepril (Lotensin), lisinopril (Prinivil) and ramipril (Altace). They also may interact with antiarrhythmic drugs given to treat an irregular heartbeat, diuretics given to treat high blood pressure, and digitalis, which also treats heart arrhythmias and heart failure.

You may also be at risk if you take certain medications for eye problems, corticosteroids or any cortisone-like medicines, or large doses of calcium or vitamin D supplements.

Most CCB interactions occur with verapamil or diltiazem because these CCBs decrease the elimination (thereby increase blood levels) of a number of drugs by the liver, in particular carbamazepine (Tegretol), used to treat seizures and neuralgia, and the cholesterol-lowering statins simvastatin (Zocor), atorvastatin (Lipitor), and lovastatin (Mevacor). This interference with liver function can result in a toxic buildup of these drugs.

Avoid smoking if you are taking CCBs, as this may result in a rapid heartbeat (tachycardia). Also, studies have shown that grapefruit juice interferes with the absorption of CCBs, so if you are going to drink grapefruit juice, you should wait at least four hours after having taken your medicine.

Alternatives

If you have high blood pressure it is unlikely that you will be prescribed CCBs as a first medication to treat it since the drugs are not as effective at lowering blood pressure as ACE inhibitors, diuretics and beta blockers. However, in African-Americans CCBs may be more effective at lowering blood pressure.