Verapamil (Isoptin, Knoll; Calan, Searle)

Verapamil is a calcium antagonist that is pharmacologically different from other currently marketed antiarrhythmics. It is used for the acute treatment of PSVT and atrial fibrillation and flutter. It appears to be more effective than beta-adrenergic blocking agents in the treatment of PSVT. Approximately 80 percent of patients with PSVT will convert to normal sinus rhythm after verapamil 0.075-0.15 mg/kg. Atrial fibrillation and flutter seldom convert to sinus rhythm with verapamil, but it successfully reduces the ventricular rate in 90 percent of these patients. Verapamil is useful for the rapid conversion of PSVT to normal sinus rhythm and for the rapid control of ventricular rate in atrial fibrillation and flutter before other antiarrhythmics have taken effect. Because of its short plasma half-life, other agents or cardioversion can be used if verapamil is unsuccessful. The use of verapamil in the treatment of classical and variant angina, hypertrophic cardiomyopathy, and hypertension is being evaluated. Mild reduction in blood pressure and heart rate may occur with verapamil therapy. Caution must be exercised when verapamil is administered to patients with sinus node disease, advanced AV block, concomitant beta-adrenergic blocking agents, and digitalis intoxication.