Amiodarone
Common Brand Names: Cordarone
Therapeutic Class: A Class III antiarrhythmic
Common Injectable Dosage Forms:
Solution for Injection: 50 mg/mL in 3, 9, 18 mL vials
Dosage Ranges:
For the treatment and prophylaxis of frequently recurring ventricular fibrillation and hemodynamically unstable ventricular tachycardia in patients refractory to other therapy and in patients unable to take oral amiodarone:
Loading Dose: Give 150 mg over the first 10 minutes (add 3 mL amiodarone injection to 100 mL D5W). Follow with a slow infusion of 360 mg over 6 hours (add 18 mg amiodarone injection to 500 mL D5W). Dosage must be individualized.
Maintenance Dose: Infuse 0.5 mg/min. (720 mg/24 hours) for up to 3 weeks.
Breakthrough Episode Dose: Infuse 150 mg over 10 minutes.
Therapeutic Concentration: 1-2.5 mg/mL
Administration and Stability: Dilute amiodarone injection with 5% Dextrose in Water (D5W) prior to use (concentration of admixture 1-6 mg/mL). Amiodarone absorbs into PVC tubing therefore use glass or polyolefin bottles for infusions lasting more than 2 hours. Do not use evacuated glass bottles for admixing since precipitation with a buffer may occur. Amiodarone may reduce the drop size of admixtures therefore use a volumetric infusion pump. Do not use a drop counter infusion set. Amiodarone injection should, whenever possible, be administered through a dedicated central venous catheter using an in-line filter. Amiodarone injection is incompatible with aminophylline, cefamandole, cefazolin, mezlocillin, heparin, and sodium bicarbonate. pH ~4.08
Pharmacology/Pharmacokinetics: Amiodarone is classified as a Class III antiarrhythmic with its primary mechanism of action being a lengthening of the cardiac action potential. It also shows some noncompetitive alpha- and beta-blocking capabilities (Class I and Class II) and negative chronotropic effects (Class IV). Amiodarone administration prolongs intranodal conduction and refractoriness of the AV node and is also a potent vasodilator. Metabolism occurs via CYP3A4 to an active metabolite, N-desethylamiodarone (DEA).
Drug and Lab Interactions: Amiodarone may increase the effects of warfarin, digoxin, quinidine, procainamide, disopyramide, fentanyl, flecainide, lidocaine, and cyclosporine. Cimetidine may increase amiodarone serum levels. Cholestyramine and phenytoin may decrease amiodarone serum levels. Amiodarone may have additive effects with beta blockers. AV block and hypotension is increased when used with calcium channel blockers.
Contraindications/Precautions: Contraindicated in patients with cardiogenic shock, marked sinus bradycardia, second- and third-degree AV block unless a functioning pacemaker is available, and in patients with an iodine sensitivity or electrolyte imbalances. Hypotensive reactions and bradycardia are related to the rate of infusion and can be minimized by slowing the infusion. Patients should be monitored for QTc prolongation during treatment. Pregnancy Category D.
Monitoring Parameters: CBC, Chest X-ray, ECG, LFTs, Eye exam, PFTs, Thyroid function.
Adverse Effects: May cause nausea, vomiting, and visual disturbances. Potentially serious adverse effects include hypotension, cardiogenic shock, cardiac arrest, congestive heart failure, bradycardia, liver function test abnormalities, ventricular tachycardia, fatal pulmonary toxicity, and AV block.
Common Clinical Applications: Amiodarone is useful to treat life-threatening ventricular arrhythmias.
