Therapeutic Classifcation Notes (CALCIUM CHANNEL BLOCKING AGENTS)

CALCIUM CHANNEL BLOCKING AGENTS

Calcium Channel Blockers interfere with the inward displacement of calcium ions through the slow channels of active cell membranes. They influence the myocardial cells, the cells within the specialized conducting system of the heart, and the cells in vascular smooth muscle.

There are important differences between the types of calcium channel blockers available as exhibited by a phenylalkylamine (verapamil), the dihydropyridines (nifedi-pine, amlodipine, felodipine, lacidipine, isradipine) and benzothiazepine (diltiazem). Verapamil is used for the treat-ment of angina, hypertension and arrhythmias. Nifedipine has more activity on the smooth muscles and blood vessels than on the myocardium. Hence it is used for angina and hypertension. Isradipine has a similar action to nifedipine but is only indicated for mild to moderate hypertension.

Diltiazem 60mg is for the prophylaxis and treatment of angina. Calcium Channel Blockers have greater activity in patients with low rennin levels. Verapamil should be used with extreme caution in combination with beta-blockers. Though gingival hyperplasia is a rare side effect, patients on long term Calcium Channel Blockers should have a good dental hygiene program. DIAZOXIDE:- A thiazide without diuretic actions; potent antihypertensive which acts by decreasing arteriole peripheral resistance with little effect on veins. Used chiefly to obtain immediate control of severe hypertension and must be given rapidly i.v. as it is so extensively bound to plasma proteins. HYDRALAZINE:-Used in severe hypertension and as a vasodilator afterload in intractable heart failure. It reduces peripheral resistance by relaxing arterioles with little effect on veins. The compensatory sympathetic discharge induced by the hypotension causes reflex tachycardia and increased cardiac output. It must therefore be used with a beta blocker and a diuretic in treating hypertension. This does not occur in the case of the failing heart.