- What are calcium channel blockers (CCBs) and how do they work?
- For what conditions are calcium channel blockers used?
- Are there any differences among calcium channel blockers?
- What are the side effects of calcium channel blockers?
- With which drugs do calcium channel blockers interact?
- What are examples of calcium channel blockers available?
What are calcium channel blockers (CCBs) and how do they work?
- The entry of calcium is critical for the conduction of the electrical signal that passes from muscle cell to muscle cell of the heart, and signals the cells to contract.
- It also is necessary in order for the muscle cells to contract and thereby pump blood.
- In the arteries, the entry of calcium into muscle cells constricts the arteries.
- Dilation of the arteries reduces blood pressure and thereby the effort the heart must exert to pump blood.
- Combined with decreases in the force of contraction, this leads to a reduced requirement for oxygen by the heart.
- Dilation of the arteries provides more oxygen-carrying blood to the heart.
- The combination of reduced demand for oxygen and increased delivery of oxygen prevents angina or heart pain. (Angina occurs when the heart is not getting enough oxygen relative to the amount of work it is doing.)
- In addition, calcium channel blockers slow electrical conduction through the heart and thereby correct abnormal rapid heartbeats.
For what conditions are calcium channel blockers used?
Calcium channel blockers are approved for treating:
- high blood pressure,
- abnormal heart rhythms (for example, atrial fibrillation, paroxysmal supraventricular tachycardia) and subarachnoid hemorrhage.
They are also used for treating other conditions such as:
Are there any differences among calcium channel blockers?
Although calcium channel blockers have a similar mechanism of action, they differ in their ability to affect heart muscle vs. arteries, and they differ in their ability to affect heart rate and contraction. These differences determine how they are used and their side effects.
- verapamil (Covera-HS, Verelan PM, Calan), and diltiazem (Cardizem LA, Tiazac) reduce the strength and rate of the heart's contraction and are used in treating abnormal heart rhythms; and
- amlodipine (Norvasc) has very little effect on the heart rate and contraction. Therefore, amlodipine is not used for treating abnormal heart rhythm, but it is preferred when heart failure is present and dilation of arteries is desired.
What are the side effects of calcium channel blockers?
Common side effects of calcium channel blockers include:
- edema (fluid accumulation in tissues),
- low blood pressure, and
Sexual dysfunction, overgrowth of gums, and liver dysfunction also have been associated with calcium channel blockers. Verapamil (Covera-HS, Verelan PM, Calan) and diltiazem (Cardizem LA, Tiazac) worsen heart failure because they reduce the ability of the heart to contract and pump blood.
With which drugs do calcium channel blockers interact?
Calcium channel blockers interact with several drugs.
- Verapamil (Covera-HS, Verelan PM, Calan) and diltiazem (Cardizem LA, Tiazac) reduce the elimination and increase the blood levels of carbamazepine (Tegretol), simvastatin (Zocor), atorvastatin (Lipitor), and lovastatin (Mevacor). This can lead to toxicity from these drugs.
- Several calcium channel blockers [for example, diltiazem (Cardizem LA, Tiazac), felodipine (Plendil)] increase the level of cyclosporine (Sandimmune, Neoral, Restasis) and similarly lead to toxicity of cyclosporine.
- Grapefruit juice (1 glass, approximately 200ml) may elevate serum concentrations of verapamil (Covera-HS, Verelan PM, Calan), felodipine (Plendil), nifedipine (Adalat, Procardia), nicardipine (Cardene), nisoldipine (Sular), and possibly amlodipine (Norvasc).
What are some examples of calcium channel blockers available?
The calcium channel blockers available in the U. S. are:
- amlodipine (Norvasc),
- diltiazem (Cardizem LA, Tiazac),
- felodipine (Plendil),
- isradipine (Dynacirc),
- nifedipine (Adalat, Procardia),
- nicardipine (Cardene),
- nimodipine (Nimotop),
- nisoldipine (Sular), and
- verapamil (Covera-HS, Verelan PM, Calan).
Verapamil, diltiazem and nicardipine (Cardene IV) also are available in intravenous formulations.
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Robert J. Bryg, MD
Board Certified Internal Medicine with subspecialty in Cardiovascular Disease