Verapamil (Isoptin, Isoptin SR, Calan, Calan SR, Covera HS)

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, 2nd or 3rd 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

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