Verapamil HCI

A to Z Drug Facts

 Actions Inhibits movement of calcium ions across cell membrane resulting in depression of mechanical contraction of myocardial and vascular smooth muscle and depression of impulse formation (automaticity) and conduction velocity.

 Indications

Oral: Treatment of vasospastic (Prinzmetal's variant), chronic stable (classic effort-associated), and unstable (crescendo, preinfarction) angina; adjunctive treatment with digitalis to control ventricular rate at rest and during stress in atrial flutter or fibrillation; prophylaxis of repetitive paroxysmal supraventricular tachycardia (PSVT); management of essential hypertension. Sustained-release: Management of essential hypertension. Parenteral: Rapid conversion of PSVTs to sinus rhythm; temporary control of rapid ventricular rate in atrial flutter or fibrillation.

Treatment of migraine and cluster headaches; treatment of hypertrophic cardiomyopathy.

 Contraindications Hypersensitivity to verapamil; sick sinus syndrome or second- or third-degree atrioventricular (AV) block except with functioning pacemaker; hypotension (less than 90 mm Hg systolic); severe left ventricular dysfunction; cardiogenic shock and severe CHF, unless secondary to supraventricular tachycardia amenable to verapamil; patients with atrial flutter or fibrillation and accessory bypass tract. IV verapamil should not be used concomitantly (within few hours) of IV beta-adrenergic blocking agents or in ventricular tachycardia.

 Route/Dosage

ADULTS: PO 40 to 160 mg tid. Do not exceed 480 mg/day. Sustained release: PO 120 to 480 mg/day. Lower doses are given once daily; larger doses divided into 2 doses.

ADULTS: IV 5 to 10 mg bolus over 2 min. May repeat with 10 mg, 30 min after first dose. Give slower (over at least 3 min) in older patients.

CHILDREN 1 to 15 yr: IV 0.1 to 0.3 mg/kg (not to exceed 5 mg) over at least 2 min. May repeat in 30 min.

CHILDREN less than 1 yr: IV 0.1 to 0.2 mg/kg (usual range, 0.75 to 2 mg) bolus over 2 min with continuous ECG monitoring.

 Interactions

Other antihypertensive agents: Additive hypotension. Beta blockers: May result in increased hypotension and adverse effects because of additive depressant effects on myocardial contractility or AV conduction. Buspirone: Pharmacologic and adverse effects may be increased by verapamil. Calcium salts: Clinical effects and toxicities of verapamil may be reversed. Carbamazepine: Increased carbamazepine serum levels. Cyclosporine: Increased cyclosporine levels may result. Dofetilide: Risk of life-threatening ventricular arrhythmias, including torsades de pointes, may be increased. Coadministration with verapamil is contraindicated. Digitalis glycosides: Increased serum digoxin or digitoxin levels may occur. Disopyramide: Do not use 48 hr before or 24 hr after verapamil. Flecainide: May prolong AV conduction. Nondepolarizing muscle relaxants: Enhanced muscle relaxant effects and prolonged respiratory depression may occur. Prazosin: Increased prazosin serum levels may result. Quinidine: Hypotension, bradycardia, ventricular tachycardia, AV block, and pulmonary edema may occur. Rifampin: Loss of effectiveness of oral verapamil may occur. IV Simvastatin: Plasma levels may be elevated by verapamil, increasing the risk of toxicity (eg, rhabdomyolysis).

Do not mix with sodium lactate in polyvinyl chloride bags, albumin, amphotericin B, hydralazine, aminophylline, sodium bicarbonate, nafcillin, or trimethoprim-sulfamethoxazole. Do not mix in solution with pH greater than 6.

 Lab Test Interferences None well documented.

 Adverse Reactions

CARDIOVASCULAR: Peripheral edema; hypotension; AV block; bradycardia; CHF; pulmonary edema; cerebrovascular accident. CNS: Dizziness; lightheadedness; headache; asthenia. DERMATOLOGIC: Dermatitis; rash; sweating; gingival hyperplasia. GI: Nausea; constipation. HEPATIC: Increased transaminases; hepatitis. RESPIRATORY: Shortness of breath; dyspnea; wheezing.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. CHILDREN: Children less than 6 mo may not respond to IV use. Rare severe hemodynamic side effects have occurred in newborns and infants after IV use. ELDERLY: May have greater hypotensive effects in elderly. Elderly may respond to lower doses. Antiplatelet effects: Calcium channel blockers may inhibit platelet function. Cardiac conduction: May be associated with variety of cardiac conduction abnormalities including first-, second-, or third-degree AV block; bradycardia; asystole; severe hypotension; nodal escape rhythms; PR prolongation; and ventricular tachycardia in patients with atrial flutter/fibrillation and W-P-W syndrome caused by antegrade conduction. CHF: Use verapamil with caution in patients with CHF. Duchenne's muscular dystrophy: May decrease neuromuscular transmission in patients with Duchenne's muscular dystrophy and prolong recovery from neuromuscular blocking agent vecuronium. Hepatic impairment: Hepatic cirrhosis can significantly alter pharmacokinetics of verapamil. Hypertrophic cardiomyopathy: Serious adverse effects were seen in patients with hypertrophic cardiomyopathy who received oral verapamil. Hypotension: Hypotension may occur during initial therapy or with dosage increases and is more likely in patients taking beta blockers. Increased intracranial pressure: IV verapamil has increased intracranial pressure in patients with supratentorial tumors at time of anesthesia induction. Premature ventricular contractions (PVCs): May occur after IV use; consider possibility with oral use. Renal impairment: Use caution.

 Administration/Storage

• Administer with milk or meals if GI upset or intolerance occurs.
• Give IV slowly over 2 min.
• Implement cardiac monitor when administering drug IV and monitor BP.
• Do not give concomitantly with IV beta-adrenergic blockers (within few hours).
• Administer Covera-HS once daily at bedtime. Swallow tablet whole; do not crush or chew.
• Store injection at room temperature, protected from light. Avoid freezing.
• Store oral form at room temperature in tight, light-resistant container.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Report any cardiovascular changes to health care provider.
• Report any chest pain to health care provider.
• If drug is to be discontinued, aid in gradual reduction of dosage.

 Patient/Family Education

• Tell patient if dose is missed to take as soon as possible. If several hours have passed or if it is nearing time for next dose, tell patient not to double dose to catch up unless advised by health care provider.
• If more than one dose is missed, tell patient to contact health care provider.
• Caution patient not to change dose unless directed by health care provider.
• Advise patient not to suddenly stop taking medication.
• Remind patient to brush and floss teeth and see dentist regularly.
• Instruct patient to report any irregular heart beat, shortness of breath, swelling of hands and feet, pronounced dizziness, constipation, nausea, or hypotension.
• Advise patient to avoid use of alcohol and OTC medications without consulting health care provider.
• Instruct patient to limit caffeine consumption.
• Advise patient that drug may cause dizziness and to use caution while driving or performing other tasks requiring mental alertness until effects of drug have stabilized.
• Stress to patient the importance of compliance in all areas of treatment regimen: diet, exercise, stress reduction, drug therapy.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts