Category:

• Calcium channel blocker

Description:

• Antihypertensive, antianginal, antidysrhthmic (Class IV)

Indications:

• Chronic stable angina, vasospastic angina, unstable angina

• Dysrhythmias (atrial flutter, atrial fibrillation, paroxysmal supraventricular tachycardia (PSVT)

• Hypertension

• Prophylaxis of migraines (non FDA approved)

Contraindications:

• Sick sinus syndrome, 2^nd or 3^rd degree heart block, hypotension <90mm Hg systolic

• Cardiogenic shock, severe CHF

Precautions:

• Pregnancy category C; excreted in breast milk; compatible with breast feeding

• CHF, hypotension, hepatic injury, children

• Renal disease, IV b-blocker therapy

• Cirrhosis, Duchenne’s muscular dystrophy

Adverse Reactions (Side Effects):

• CNS: asthenia, dizziness, headache, lightheadedness

• CV: AV block, bradycardia, CHF, edema, hypotension, palpitations

• GI: constipation, nausea

• GU: nocturia, polyuria

• SKIN: rash

Dosage:

Administered orally, intravenously

Adult:            

• Angina: PO initial 80-120mg 3 times daily; titrate to 480mg daily based on response (adjust dose weekly)

• Dysrhythmias (atrial fibrillation/digitalized): PO 240-320mg daily in 3-4 divided doses

• Dysrhythmias (supraventricular tachycardia): IV bolus initial 5-10mg over 2 minutes, repeat dose 10mg 30mg after first if ineffective

• Hypertension:PO 80mg 2 times daily initially, increase as needed to 480mg daily in 2 divided doses; SUS REL 180-240mg once daily initially, increase as needed up to 360mg daily

Child 0-1 year: 

• Dysrhythmias (PSVT): IV bolus 0.1-0.2 mg/kg over > 2 minutes with ECG monitoring; repeat if necessary in 30 minutes

Child 1-15 years: 

• Dysrhythmias (PSVT): IV bolus 0.1-0.3 mg/kg over >2 minutes; repeat in 30 minutes; not to exceed 10mg in a single dose

Drug interactions:

• Carbamazepine: increased carbamazepine toxicity when verapamil added to chronic anticonvulsant regimens; decreased metabolism

• Amiodarone: cardiotoxicity with bradycardia and decreased cardiac output

• Barbiturates: reduced plasma concentrations of verapamil

• Beta-blockers: Beta-blocker serum concetraions increased; increased risk of bradycardia or hypotension

• Calcium: inhibited activity of verapamil

• Digitalis glycosides: increased digoxin concentrations by approximately 70%

• Doxazosin, prazosin, terazosin: enhanced hypotensive effects

• Ethanol: increased ethanol concentrations, prolonged and increased levels of intoxication

• Lithium: potential for neurotoxicity

• Neuromuscular blocking agents: prolonged neuromuscular blockade

• Quinidine: quinidine toxicity via inhibition of metabolism

• Rifampin, rifabutin: induced metabolism; reduced verapamil concentrations

• Theophylline: verapamil inhibits metabolism, increases theophylline levels