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 that the heart must do. By dilating the arteries, calcium channel blockers or 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, calcium channel blockers relieve or prevent angina. Calcium channel blockers also are used for treating high blood pressure because of their blood pressure-lowering effects. Calcium channel blockers decrease the excitability of heart muscle and are therefore used for treating certain types of abnormally rapid heart rhythms.
What calcium channel blockers are available?
Calcium channel blockers that have been approved for use in the US include:
- amlodipine (Norvasc)
- amlodipine and atorvastatin (Caduet)
- amlodipine and benazepril (Lotrel)
- amlodipine and valsartan (Exforge)
- amlodipine and telmisartan (Twynsta)
- amlodipine and olmesartan (Azor)
- amlodipine and olmesartan and hydroclorothiazide (Tribenzor)
- amlodipine and aliskiren and hydroclorothiazide
- amlodipine and perindopril (Prestalia)
- clevidipine (Cleviprex)
- diltiazem (Cardizem)
- felodipine (Cardene, Cardene SR)
- isradipine
- nicardipine
- nimodipine
- nisoldipine (Sular)
- verapamil (Calan)
Discontinued brands in the US:
Are there any differences among calcium channel blockers?
Calcium channel blockers 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 calcium channel blockers (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.
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For what conditions are calcium channel blockers used?
Calcium channel blockers are used for treating:
- High blood pressure
- Angina
- Abnormal heart rhythms (for example, atrial fibrillation, and 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, calcium channel blockers have not been shown to reduce mortality or additional heart attacks after a heart attack.
Calcium channel blockers are as effective as ACE inhibitors in reducing blood pressure, but they may not be as effective as ACE inhibitors in preventing the kidney failure caused by high blood pressure or diabetes.
Calcium channel blockers may be more effective for people of African descent than other blood pressure medications.
They also are used for treating:
- Pulmonary hypertension
- Raynaud's syndrome
- Cardiomyopathy
- Subarachnoid hemorrhage
Calcium channel blockers are also used in the prevention of migraine headaches.
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What are the side effects of calcium channel blockers?
The most common side effects of calcium channel blockers are:
- Constipation
- Nausea
- Headache
- Fatigue
- Rash
- Edema (swelling of the legs and feet with fluid)
- Pulmonary edema
- Low blood pressure
- Drowsiness
- Dizziness
- Muscle weakness
- Muscle cramps
- Abnormal heartbeats
Liver dysfunction and over growth of the gums also occurs.
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, calcium channel blockers are associated with sexual dysfunction.
Which drugs interact with calcium channel blockers?
Calcium channel blockers interact with verapamil (Calan, Isoptin) or diltiazem (Cardizem). The interaction occurs because verapamil and diltiazem decrease the elimination of a number of drugs by the liver. Through this mechanism, verapamil and diltiazem may 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.
Grapefruit juice (approximately 200 ml) may elevate blood concentrations of felodipine (Plendil), verapamil (Calan, Isoptin), nisoldipine (Sular), nifedipine (Adalat, Procardia), nicardipine (Cardene), and possibly amlodipine (Norvasc). Grapefruit juice should not be consumed within 2 hours before or 4 hours after administration of affected calcium channel blockers.