Amiodarone

Amiodarone (Cordarone^®)

 

Class:	Potassium channel blocker (Antidysrhythmic Drug Class III)
Actions:	Blocks potassium channels in phase 3 of the action potential Delays repolarization of fast action potential; prolong action potential Prolongs QT interval Decreases heart rate (negative chronotropic) Decreases contractility (negative inotropic)
Indications:	Pulseless ventricular fibrillation or ventricular tachycardia (ACLS 1st line choice for IV antidysrhythmic agent) Unstable ventricular tachycardia Has been indicated in the past for supraventricular tachycardias–but has been moved down due to risks of toxicity Atrial fibrillation (oral doses)
Pharmacokinetics:	Onset: 2 hours (IV); 2-3 days (orally) Peak:  3-7 hours Half-Life:  25 – 110 days (generally 58 days)  THIS IS A VERY LONG HALF LIFE!–which increases the risk for toxicity!
Adverse Effects:	Muscle weakness, fatigue, tremor, peripheral neuropathies, tingling sensations Blue-gray discoloration of the skin (3-5%) Prolonged QT interval and PR interval Hypotension, sinus arrest, heart failure, AV blocks, dysrhythmias Anorexia, nausea, vomiting, constipation, hepatotoxicity Photosensitivity, corneal microdeposits, optic neuropathy, blindness Fatal gasping syndrome (IV) with children
Signs of Toxicity:	Pulmonary toxicity:  (2-17%) hypersensitivity pneumonitis, pulmonary fibrosis (dyspnea, cough, chest pain) Cardiotoxicity:  sinus bradycardia, AV blocks, torsades de pointes, heart failure Hepatitis, thyroid dysfunction
Contraindications:	Cardiogenic shock Severe sinus bradycardia Hypersensitivity to benzyl alcohol Use cautiously in hepatic or thyroid disease. Safety during pregnancy, lactation or with children not established (Category D).
Dosages & Routes:	PO: 800-1600 mg daily (loading);  100 – 400 mg daily (maintenance) IV bolus:  300 mg IV or IO in 20-30 ml D5W; 2nd dose of 150 mg may be given in 3-5 minutes
Nursing Implications:	Drug Interactions:  1)Amiodarone increases serum levels of quinidine, procainamide, phenytoin, digoxin, diltiazem, warfarin, cyclosporine, lovastatin, simvastatin, & atorvastatin; 2) Amiodarone serum levels are increased by grapefruit and inhibitors of CYP3A4 enzyme; 3) Amiodarone serum levels are decreased by cholestyramine, St. John's wart, rifampin; 4) Risk for severe dysrhythmia increases with diuretics which deplete potassium or magnesium; 5) Severe cardiac impairment (bradycardia or heart failure) can occur if combined with beta blocker or calcium channel blocker. Drug Incompatibilities:  nitroprusside, sodium bicarbonate, aminophylline, ampicillin, cephalosporins, digoxin, heparin Monitor blood pressure and apical pulse prior to administration. Cardiac monitor should be used on patients receiving amiodarone therapy. Baseline chest x-ray and pulmonary function test is recommended before beginning PO therapy. Baseline assessments should be checked of liver function and thyroid function. Initial therapy should be implemented under hospital precautions with access to advanced life support. Monitor serum level frequently. Encourage patient to wear sunglasses for photosensitivity. Encourage patient to wear protective clothing and sunscreen when outdoors. Caution patient/family about using OTC herbal products (e.g., St. John's wart, echinacea). Patient should obtain ophthalmic exam regularly.

 

References:

American Heart Association. (2006). Handbook of Emergency Cardiac Care (p. 45). Salem, MA: AHA.

Dirks, J.L. (2010) Cardiovascular therapeutic management.  In L.D. Urden, K.M. Stacy, & M.E. Lough's (Eds.) Critical care nursing: Diagnosis and management (6th ed., pp. 544-545).  St. Louis: Mosby Elsevier.

Lehne, R.A. (2010). Pharmacology for nursing care (7th ed., pp. 546-547).  St. Louis: Saunders Elsevier.

Wilson, B.A., Shannon, M.T., Shields, K.M., & Stang, C.L. (2007).  Prentice Hall Nurse's Drug Guide 2007 (pp. 1070-1073).  Upper Saddle River, NJ: Pearson Prentice Hall.

 

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