Calcium Channel Blockers

Calcium Channel Blockers

Discuss Calcium Channel Blockers.
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Write Short Note On Calcium Channel Blockers.
Answer:

There are three subclasses of calcium channel blockers:

1. Phenylalkylamines: Verapamil
2. Benzothiazepines: Diltiazam
3. Dihydropyridines: Nifedipine, amlodipine nicardipine, pelodipine, isradipine, nisoldipine.

Calcium Channel Blockers Mechanism Of Action

• Smooth muscle relaxants: The movement of calcium inside cardiac muscle cells released more calcium from the sarcoplasmic reticulum causing excitation-contraction coupling.
• Calcium channel blockers block all types of calcium channels and decrease the availability of calcium ions thus causing the relaxation of smooth muscle cells or cardiac cells. The effect is more on arterioles and less on veins.

Calcium Channel Blockers: Mechanism of Action, Uses, and Side Effects

Negative, Chronotropic, Ionotropic And Dromotropic Action

• Calcium channel blockers inhibit calcium movement inside the cell in the depolarization phase thus inhibiting the contraction of cardiac muscle. Cardiac work and oxygen consumption are decreased.
• Calcium channel blockers inhibit the refractory period of the AV node, decrease SA nodal discharge suppresses ectopic foci producing Antiarrhythmic action.

Calcium Channel Blockers: Types, Indications, and Dosage

Uses Of Calcium Channel Blockers

• Angina pectoris: It is useful in both types of angina, i.e. classical and variant angina.
• Hypertension: They are fist line drugs in hypertension. Calcium channel blockers decrease total peripheral resistance and hence decrease BP.
• Arrhythmias: Calcium channel blockers are preferred in supraventricular tachycardia.
• Calcium channel blockers are also used in hypertensive emergencies.
• Hypertrophic cardiomyopathy: Verapamil improves diastolic function.
• Migraine: Flunarizine reduces the frequency of migraine attacks. Verapamil is used as a prophylactic drug.