Name
- Verapamil.
Class of drug
- Calcium channel blocker.
- Class IV antidysrhythmic agent.
Uses
Action
- Systemic resistance vessels and large arteries respond to calcium channel blockers more readily than venous capacitance vessels and pulmonary vasculature.
- Verapamil causes reduction in myocardial contractility (negative inotrope), depressed electrical activity (retards AV conduction) and vasodilation (cardiac vessels and peripheral arteries and arterioles).
- Verapamil is often used as a second choice calcium channel blocker behind diltiazem as it has a more pronounced negative inotropic effect.
- A calcium channel-blocker which acts by interfering with the inward movement of calcium ions through the slow channels in myocardial cells and cells within the specialised conducting cells in the heart and vascular smooth muscle.
- Vascular smooth muscle is as sensitive to verapamil as myocardial tissues (relative activity of 1:1).
Indications
- Primarily used to control supraventricular tachycardias, sustained and paroxysmal ventricular tachycardias particularly in cases of hypertrophic cardiomyopathy
, and the heart rate in dogs with atrial fibrillation as an adjunct to digoxin . - Management of feline hypertrophic cardiomyopathy ; calcium channel blockers are preferred to propanolol by some authors because they improve myocardial relaxation, increase ventricular filling and dilate coronary vasculature.
- Management of hypertension ; effective but to a lesser degree than diltiazem .
