Amiodarone Hydrochloride (4 brand names, 2 dosage forms, 2 routes)
Available dosage forms: TABLET, INJECTABLE.
Routes of administration: ORAL, INJECTION.
Brand Names
- AMIODARONE HYDROCHLORIDE
- CORDARONE
- NEXTERONE
- PACERONE
Indications and Usage
NEXTERONE is indicated for initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation (VF) and hemodynamically unstable ventricular tachycardia (VT) in patients refractory to other therapy.
Contraindications
NEXTERONE is contraindicated in patients with: •Known hypersensitivity to any of the components of NEXTERONE Premixed Injection, including iodine [ see Warnings and Precautions (5.8) ]. •Cardiogenic shock. •Marked sinus bradycardia. •Second- or third-degree atrioventricular (AV) block unless a functioning pacemaker is available.
Adverse Reactions
The following adverse reactions are described elsewhere in labeling: •Hypotension [see Warnings and Precautions (5.2) ] •Hepatic injury [see Warnings and Precautions (5.4) ] •Proarrhythmia [see Warnings and Precautions (5.5) ] •Pulmonary injury [see Warnings and Precautions (5.6) ] •Thyroid injury [see Warnings and Precautions (5.8) ] •Hypersensitivity [see Warnings and Precautions (5.10) ]
Drug Interactions
Drug interactions with amiodarone are described in Table 5 below. Table 5: Amiodarone Drug Interactions Concomitant Drug Class/Name Examples Clinical Comment QT Prolonging Drugs class I and III antiarrhythmics, lithium, certain phenothiazines, tricyclic antidepressants, certain fluoroquinolone and macrolide antibiotics, azole antifungals, halogenated inhalation anesthetic agents Increased risk of Torsade de Pointes. Avoid concomitant use. Negative Chronotropes digoxin, beta blockers, verapamil, diltiazem, clonidine, ivabradine Potentiates the electrophysiologic and hemodynamic effects of amiodarone, resulting in bradycardia, sinus arrest and AV block. Monitor heart rate. CYP450 Inhibitors Grapefruit juice, certain fluoroquinolone and macrolide antibiotics, azole antifungals, cimetidine Increased exposure of amiodarone. Avoid concomitant use. CYP450 Inducers St. John’s Wort Reduced amiodarone serum levels Cyclosporine Increased plasma levels of cyclosporine have been reported resulting in elevated creatinine, despite reduction of cyclosporine dose. Monitor cyclosporine drug levels and renal function with concomitant use. Cholestyramine Reduced amiodarone serum levels Antiarrhythmics quinidine, procainamide, flecainide Reserve concomitant use for patients who are unresponsive to a single agent. Antiarrhythmic metabolism inhibited by amiodarone. Initiate antiarrhythmic at a lower than usual dose and monitor patient carefully. Reduce dose levels of previously administered antiarrhythmic by 30 to 50% for several days after transitioning to oral amiodarone. Evaluate continued need for antiarrhythmic. Digoxin Increased digoxin concentration. Reduce digoxin by half or discontinue. If continued, monitor for evidence of toxicity. HMG-CoA Reductase Inhibitors simvastatin, lovastatin, atorvastatin Increased plasma concentration of HMG-CoA reductase inhibitor. Limit the dose of lovastatin to 40 mg.Limit the coadministered dose of simvastatin to 20 mg.Lower starting dose of other
Mechanism of Action
Amiodarone is considered a class III antiarrhythmic drug, but it possesses electrophysiologic characteristics of all four Vaughan Williams classes. Like class I drugs, amiodarone blocks sodium channels at rapid pacing frequencies, and like class II drugs, amiodarone exerts a noncompetitive antisympathetic action. One of its main effects, with prolonged administration, is to lengthen the cardiac action potential, a class III effect. The negative chronotropic effect of amiodarone in nodal tissues is similar to the effect of class IV drugs. In addition to blocking sodium channels, amiodarone blocks myocardial potassium channels, which contributes to slowing of conduction and prolongation of refractoriness. The antisympathetic action and the block of calcium and potassium channels are responsible for the negative dromotropic effects on the sinus node and for the slowing of conduction and prolongation of refractoriness in the atrioventricular (AV) node. Its vasodilatory action can decrease cardiac workload and consequently myocardial oxygen consumption. Intravenous amiodarone administration prolongs intranodal conduction (Atrial-His, AH) and refractoriness of the atrioventricular node (ERP AVN) but has little or no effect on sinus cycle length (SCL), refractoriness of the right atrium and right ventricle (ERP RA and ERP RV), repolarization (QTc), intraventricular conduction (QRS), and infra-nodal conduction (His-ventricular, HV). A comparison of the electrophysiologic effects of intravenous amiodarone and oral amiodarone is shown in the table below. Table 5: EFFECTS OF INTRAVENOUS AND ORAL AMIODARONE ON ELECTROPHYSIOLOGIC PARAMETERS Formulation SCL QRS QTc AH HV ERPRA ERPRV ERPAVN Intravenous ↔ ↔ ↔ ↑ ↔ ↔ ↔ ↑ Oral ↑ ↔ ↑ ↑ ↔ ↑ ↑ ↑ ↔No change At higher doses (>10 mg/kg) of intravenous amiodarone, prolongation of the ERP RV and modest prolongation of the QRS have been seen. These differences between oral and IV administration suggest that the initial acute effects of intrave
Overdosage
There have been cases, some fatal, of amiodarone overdose. Effects of an inadvertent overdose of intravenous amiodarone include hypotension, cardiogenic shock, bradycardia, AV block, and hepatotoxicity. Treat hypotension and cardiogenic shock by slowing the infusion rate or with standard therapy: vasopressor drugs, positive inotropic agents, and volume expansion. Bradycardia and AV block may require temporary pacing. Monitor hepatic enzyme concentrations closely. Neither amiodarone nor DEA is dialyzable.