Calcium Channel Blockers
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Calcium channel blockers are drugs that mainly lower blood pressure by either preventing calcium from entering cells of the cardiac muscle, or the smooth muscle cells of the blood vessel walls. Some of these drugs also target nerve cells and they are used as antiepileptics.
General pharmacology
When calcium channel blockers bind to cardiac muscle cells, they prevent calcium from entering them. The result is a decrease of contraction and conduction of the heart, and a decrease of heart rate.
When calcium channel blockers bind to smooth muscles of blood vessels, they cause them to relax and widen (vasodilatation), therefore lowering blood pressure.
There are three classes of calcium channel blockers. Dihydropyridines are relatively selective to muscle cells of blood vessels. They can be easily identified by the suffix “-dipine”. These drugs are primarily used to treat high blood pressure. They are not generally prescribed to patients suffering from angina because one of their side effects is reflex cardiac stimulation which can increase cardiac demand in oxygen. Amlodipine and nifedipine are exceptions in the dihydropyridine class used to treat angina.
Phenylalkylamines are relatively selective to cardiac muscle cells. By reducing contraction and oxygen demand, these drugs are often used to treat angina. Phenylalkylamines have little effects on blood vessels.
Benzothiazepines are part of an intermediate class. They have both cardiac effects and blood vessel relaxation action, without the reflex cardiac stimulation caused by dihydropyridines.
Examples of calcium channel blockers
Examples of dihydropyridines include:
- Amlodipine (Norvasc, Azor).
- Aranidipine (Sapresta).
- Azelnidipine (Calblock).
- Barnidipine (HypoCa).
- Benidipine (Coniel).
- Cilnidipine (Atelec, Cinalong, Siscard).
- Clevidipine (Cleviprex).
- Efonidipine (Landel).
- Felodipine (Plendil).
- Lacidipine (Motens, Lacipil).
- Manidipine (Calslot, Madipine).
- Nicardipine (Cardene, Carden SR).
- Nifedipine (Procardia, Adalat).
- Nilvadipine (Nivadil).
- Nimodipine (Nimotop).
- Nisoldipine (Baymycard, Sular, Syscor).
- Nitrendipine (Cardif, Nitrepin, Baylotensin).
- Pranidipine (Acalas).
Examples of phenylalkylamines include:
- Verapamil (Calan, Isoptin).
- Gallopamil (Procorum, D600).
An example of benzothiazepines:
- Diltiazem (Cardizem).
Therapeutic indications
Calcium channel blockers are usually prescribed to treat hypertension, angina and arrhythmia. Other conditions can also be treated with these drugs.
Doctors recommend calcium channel blockers to treat:
- Hypertension (high blood pressure).
- Angina (chest pain).
- Arrhythmia (irregular heartbeats).
- Brain aneurysm complications.
- Migraines.
- Some circulatory conditions, such as Raynaud's disease (disorder that affects blood flow to the fingers, toes, nose and ears, when exposed to cold).
- Pulmonary hypertension (high blood pressure that affects the arteries in the lungs).
Side effects
Common side effects of calcium channel blockers include:
- Constipation.
- Excessive hypotension (low blood pressure).
- Oedema (Swelling in the feet and lower legs).
- Tachycardia (rapid heartbeat).
- Rash.
- Drowsiness.
- Flushing (red face and other areas of the skin).
- Nausea.
Cautions
The cardiac selective, non-dihydropyridine calcium channel blockers can cause excessive bradycardia (slow heart beat), impaired electrical conduction, and depressed contractility. Therefore, patients having pre-existent bradycardia, conduction defects, or heart failure caused by heart dysfunction should not be given calcium channel blockers, especially the cardiac selective ones.
Calcium channel blockers, especially non-dihydropyridines, should not be prescribed to patients being treated with a beta blocker because beta blockers also depress cardiac electrical and mechanical activity. Taking a calcium channel blocker therefore increases the effects of beta blockers.
Major drug groups
Cardiovascular system
References
Sélection Reader's Digest, Le Guide canadien des médicaments, 2002.
Wikipedia, the free encyclopedia (www.wikipedia.org).
Mayo Clinic, medical information and tools for better living (www.mayoclinic.com).
CV Pharmacology, cardiovascular pharmacology concepts (www.cvpharmacology.com).
The information above should be used as a reference only. Any medical decision should not be done before consulting a health care professional.
Last update: 29th of July 2009.