Calcium Channel Blocker

Calcium channel blockers are a class of drugs with effects on many excitable cells of the body, like the muscle of the heart, smooth muscles of the vessels or neuron cells. The latter are used as antiepileptics and are not covered in this article.

The main action of calcium channel blockers is to decrease the blood pressure. It is for this action that it is used in individuals with hypertension.

Explanation
Most calcium channel blockers decrease the force of contraction of the myocardium (muscle of the heart). This is known as the negative inotropic effect of calcium channel blockers. It is because of the negative inotropic effects of most calcium channel blockers that they are avoided (or used with caution) in individuals with cardiomyopathy.

Many calcium channel blockers also slow down the conduction of electrical activity within the heart, by blocking the calcium channel during the plateau phase of the action potential of the heart (see: cardiac action potential). This is known as a negative dromotropic effect. It causes a lowering of the heart rate and may cause heart blocks, which is known as the negative chronotropic effect of calcium channel blockers. The negative chronotropic effects of calcium channel blockers make them a commonly used class of agents in individuals with atrial fibrillation or flutter in whom control of the heart rate is an issue.

Mechanism of action
Calcium channel blockers work by blocking L-type voltage gated calcium channels (VGCC) in the heart and in the blood vessels. This prevents calcium levels from increasing as much in the cells when stimulated, leading to less contraction.

This decreases total peripheral resistance by dilating the blood vessels, and decreases cardiac output by lowering the force of contraction. Because resistance and output drop, so does blood pressure.

With low blood pressure, the heart does not have to work as hard; this can ease problems with cardiomyopathy and coronary disease.

Unlike with beta-blockers, the heart is still responsive to sympathetic nervous system stimulation, so blood pressure can be maintained more effectively.

Dihydropyridine
Dihydropyridine calcium channel blockers are often used to reduce systemic vascular resistance and arterial pressure, but are not used to treat angina because the vasodilation and hypotension can lead to reflex tachycardia. This CCB class is easily identified by the suffix "-pine".
 * Amlodipine (Norvasc)
 * Felodipine (Plendil)
 * Nicardipine (Cardene, Carden SR)
 * Nifedipine (Procardia, Adalat)
 * Nimodipine (Nimotop)
 * Nisoldipine (Sular)
 * Nitrendipine (Cardif, Nitrepin)
 * Lacidipine (Motens)
 * Lercanidipine (Zanidip)

Side effects of these synthetic drugs may include but are not limited to:
 * Dizziness, headache, redness in the face
 * Fluid buildup in the legs
 * Rapid heart rate.
 * Slow heart rate.
 * Constipation

Phenylalkylamine
Phenylalkylamine calcium channel blockers are relatively selective for myocardium, reduce myocardial oxygen demand and reverse coronary vasospasm, and are often used to treat angina. They have minimal vasodilatory effects compared with dihydropyridines. Action is intracellular.
 * Verapamil (Calan, Isoptin)
 * Gallopamil (D600)

Benzothiazepine
Benzothiazepine calcium channel blockers are an intermediate class between phenylalkylamine and dihydropyridines in their selectivity for vascular calcium channels. By having both cardiac depressant and vasodilator actions, benzothiazepines are able to reduce arterial pressure without producing the same degree of reflex cardiac stimulation caused by dihydropyridines.
 * Diltiazem (Cardizem)

Other

 * Menthol (mint oil)

Other drugs with similar uses
Other classes of pharmaceutical agents that have overlapping effects as calcium channel blockers include ACE inhibitors, beta-blockers, and nitrates.