What is the effect of Verapamil (Calcium Channel Blocker)?

From the Guidelines

Verapamil, a calcium channel blocker, is recommended for patients with unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI) who are unable to tolerate adequate doses of nitrates and beta blockers, or have variant angina, due to its beneficial effects on decreasing myocardial oxygen demand and improving myocardial flow 1.

Key Points

• Verapamil reduces cell transmembrane inward calcium flux, inhibiting myocardial and vascular smooth muscle contraction, and has prominent AV and sinus node effects 1.
• The medication is believed to have beneficial effects in UA/NSTEMI due to decreased myocardial oxygen demand and improved myocardial flow, related to coronary arterial and arteriolar dilation 1.
• Major side effects of verapamil include hypotension, worsening heart failure, bradycardia, and AV block, and it should be avoided in patients with pulmonary edema or evidence of severe left ventricular dysfunction 1.

Clinical Use

• Verapamil may be used to control ongoing or recurring ischemia-related symptoms in patients with UA/NSTEMI, and has been used for the management of hypertension in patients with recurrent UA 1.
• The medication has been studied in several randomized trials, including the Danish Study Group on Verapamil in Myocardial Infarction (DAVIT) and the Diltiazem Reinfarction Study (DRS), which found that it relieves or prevents signs and symptoms of ischemia to a degree similar to beta blockers 1.
• Meta-analyses combining UA/NSTEMI studies of all calcium channel blockers have suggested no overall benefit, whereas those excluding nifedipine have reported favorable effects on outcomes for verapamil alone 1.

From the FDA Drug Label

Verapamil hydrochloride is a calcium ion influx inhibitor (slow-channel blocker or calcium ion antagonist) that exerts its pharmacologic effects by modulating the influx of ionic calcium across the cell membrane of the arterial smooth muscle as well as in conductile and contractile myocardial cells Verapamil exerts antihypertensive effects by decreasing systemic vascular resistance, usually without orthostatic decreases in blood pressure or reflex tachycardia; bradycardia (rate less than 50 beats/min) is uncommon (1. 4%). Verapamil hydrochloride dilates the main coronary arteries and coronary arterioles, both in normal and ischemic regions, and is a potent inhibitor of coronary artery spasm, whether spontaneous or ergonovine-induced Verapamil hydrochloride regularly reduces the total systemic resistance (afterload) against which the heart works both at rest and at a given level of exercise by dilating peripheral arterioles. Electrical activity through the AV node depends, to a significant degree, upon calcium influx through the slow channel By decreasing the influx of calcium, verapamil hydrochloride prolongs the effective refractory period within the AV node and slows AV conduction in a rate-related manner.

The effect of Verapamil (Calcium Channel Blocker) is to:

• Decrease systemic vascular resistance and lower blood pressure
• Dilate coronary arteries and inhibit coronary artery spasm
• Reduce total systemic resistance and afterload
• Prolong the effective refractory period within the AV node and slow AV conduction
• Induce antihypertensive effects without significant orthostatic decreases in blood pressure or reflex tachycardia 2, 2, 2

From the Research

Effects of Verapamil

• Verapamil is effective in patients with supraventricular tachyarrhythmias, hypertrophic cardiomyopathy, and various anginal syndromes 3
• It is also used in the management of atrial tachyarrhythmias, angina, and possibly hypertension 4
• Verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes 5
• It produces generalized systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure 5

Therapeutic Uses

• Verapamil is used as a first-line treatment for mild to moderate essential hypertension 5
• It is effective in the treatment of patients with stable angina pectoris 6
• Verapamil may be used as an alternative to beta-blockers in selected patients as late start secondary prevention after acute myocardial infarction 6
• It has a potential role in preventing recurrent stenosis after percutaneous transluminal coronary angioplasty (PTCA) 6

Pharmacological Properties

• Verapamil is a phenylalkylamine derivative that antagonizes calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes 5
• It has negative inotropic, chronotropic, and dromotropic effects 7
• Verapamil does not cause bronchoconstriction, making it a suitable option for patients with asthma or chronic obstructive airway disease 5
• It does not cause reflex tachycardia, orthostatic hypotension, or development of tolerance 5