Amiodarone

1 INDICATIONS AND USAGE Pacerone is indicated for the treatment of documented, life-threatening recurrent ventricular fibrillation and life-threatening recurrent hemodynamically unstable tachycardia in adults who have not responded to adequate doses of other available antiarrhythmics or when alternative agents cannot be tolerated. Pacerone is an antiarrhythmic indicated for: Recurrent ventricular fibrillation. ( 1 ) Recurrent hemodynamically unstable ventricular tachycardia. ( 1 )

12.1 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. Pacerone prolongs the duration of the action potential of all cardiac fibers while causing minimal reduction of dV/dt (maximal upstroke velocity of the action potential). The refractory period is prolonged in all cardiac tissues. Amiodarone hydrochloride increases the cardiac refractory period without influencing resting membrane potential, except in automatic cells where the slope of the prepotential is reduced, generally reducing automaticity. These electrophysiologic effects are reflected in a decreased sinus rate of 15% to 20%, increased PR and QT intervals of about 10%, the development of U-waves, and changes in T-wave contour. These changes should not require discontinuation of Pacerone as they are evidence of its pharmacological action, although Pacerone can cause marked sinus bradycardia or sinus arrest and heart block [see Warnings and Precautions (5.4) ] . Hemodynamics In animal studies and after intravenous administration in man, amiodarone hydrochloride relaxes vascular smooth muscle, reduces peripheral vascular resistance (afterload), and slightly increases cardiac index. After oral dosing, however, amiodarone hydrochloride produces no significant change in left ventricular ejection fraction (LVEF), even in patients with depressed LVEF. After acute intravenous dosing in man, amiodarone hydrochloride may have a mild negative inotropic effect.

2 DOSAGE AND ADMINISTRATION Dosage must be individualized based on severity of arrhythmia and response. Use the lowest effective dose. Obtain baseline chest x-ray, pulmonary function tests, thyroid function tests, and liver aminotransferases. Correct hypokalemia, hypomagnesemia, and hypocalcemia before initiating treatment. Initiate treatment with a loading dose of 800 to 1600 mg/day until initial therapeutic response occurs (usually 1 to 3 weeks). Once adequate arrhythmia control is achieved, or if side effects become prominent, reduce Pacerone tablets dose to 600 to 800 mg/day for one month and then to the maintenance dose, usually 400 mg/day. ( 2 ) Recommended Dosage: Initiate treatment with a loading dose of 800 to 1600 mg/day until initial therapeutic response occurs (usually 1 to 3 weeks). Once adequate arrhythmia control is achieved, or if side effects become prominent, reduce Pacerone tablet dose to 600 to 800 mg/day for one month and then to the maintenance dose, usually 400 mg/day. Administration: Administer Pacerone tablets consistently with regard to meals [see Clinical Pharmacology (12.3) ] . Administration of Pacerone tablets in divided doses with meals is suggested for total daily doses of 1000 mg or higher, or when gastrointestinal intolerance occurs.

6 ADVERSE REACTIONS The following serious adverse reactions are described in more detail in other sections of the prescribing information: Pulmonary Toxicity [see Warnings and Precautions (5.2) ] Hepatic Injury [see Warnings and Precautions (5.3) ] Worsened Arrhythmia [see Warnings and Precautions (5.4) ] Visual Impairment and Loss of Vision [see Warnings and Precautions (5.5) ] Thyroid Abnormalities [see Warnings and Precautions (5.6) ] Bradycardia [see Warnings and Precautions (5.7) ] Peripheral Neuropathy [see Warnings and Precautions (5.10) ] Photosensitivity and Skin Discoloration [see Warnings and Precautions (5.11) ] The most common reactions (>1%) leading to discontinuation of amiodarone include pulmonary toxicity, paroxysmal ventricular tachycardia, congestive heart failure, and elevation of liver enzymes. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Upsher-Smith Laboratories, LLC at 1-855-899-9180 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. At the usual maintenance dose (400 mg/day) and above, amiodarone hydrochloride causes adverse reactions in about three-fourths of all patients, resulting in discontinuation in 7% to 18%. In surveys of almost 5,000 patients treated in open U.S. studies and in published reports of treatment with amiodarone hydrochloride, the adverse reactions most frequently requiring discontinuation of amiodarone hydrochloride included pulmonary infiltrates or fibrosis, paroxysmal ventricular tachycardia, congestive heart failure, and elevation of liver enzymes. Other symptoms causing discontinuations less often included visual disturbances, photosensitivity, blue skin discoloration, hyperthyroidism, and hypothyroidism. The following side-effect rates are based on a retrospective study of 241 patients treated for 2 to 1,515 days (mean 441.3 days): Thyroid Common: Hypothyroidism, hyperthyroidism. Cardiovascular Common: Congestive heart failure, cardiac arrhythmias, SA node dysfunction. Gastrointestinal Very common: Nausea, vomiting. Common: Constipation, anorexia, abdominal pain. Dermatologic Common: Solar dermatitis/photosensitivity. Neurologic Common: Malaise and fatigue, tremor/abnormal involuntary movements, lack of coordination, abnormal gait/ataxia, dizziness, paresthesias, decreased libido, insomnia, headache, sleep disturbances. Ophthalmic Common: Visual disturbances. Hepatic Common: Abnormal liver-function tests, nonspecific hepatic disorders. Respiratory Common: Pulmonary inflammation or fibrosis. Other Common: Flushing, abnormal taste and smell, edema, abnormal salivation, coagulation abnormalities. Uncommon: Blue skin discoloration, rash, spontaneous ecchymosis, alopecia, hypotension, and cardiac conduction abnormalities. 6.2 Post-marketing Experience The following adverse reactions have been identified during post-approval use of amiodarone hydrochloride. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Hematologic: hemolytic anemia, aplastic anemia, pancytopenia, neutropenia, thrombocytopenia, agranulocytosis, granuloma. Immune: anaphylactic/anaphylactoid reaction (including shock), angioedema. Neurologic: pseudotumor cerebri, parkinsonian symptoms such as akinesia and bradykinesia (sometimes reversible with discontinuation of therapy), demyelinating polyneuropathy. Psychiatric: hallucination, confusional state, disorientation, delirium. Cardiac: hypotension (sometimes fatal), sinus arrest. Respiratory: eosinophilic pneumonia, acute respiratory distress syndrome in the post-operative setting, bronchospasm, bronchiolitis obliterans o

5 WARNINGS AND PRECAUTIONS Persistence of Adverse Effects: Adverse reactions and drug interaction can persist for several weeks following discontinuation. ( 5.1 ) Impaired Vision: Corneal microdeposits (common; reversible), optic neuropathy/neuritis (rare; may lead to blindness). ( 5.5 ) Thyroid Abnormalities: Hyperthyroidism or hypothyroidism. ( 5.6 ) 5.1 Persistence of Adverse Effects Because of the long half-life of amiodarone (15 to 142 days) and its active metabolite desethylamiodarone (14 to 75 days), adverse reactions and drug interactions can persist for several weeks following amiodarone discontinuation [see Clinical Pharmacology (12.3) ] . 5.2 Pulmonary Toxicity Pacerone may cause a clinical syndrome of cough and progressive dyspnea accompanied by functional, radiographic, gallium-scan, and pathological data consistent with pulmonary toxicity. Pulmonary toxicity secondary to Pacerone may result from either indirect or direct toxicity as represented by hypersensitivity pneumonitis (including eosinophilic pneumonia) or interstitial/alveolar pneumonitis, respectively. Rates of pulmonary toxicity have been reported to be as high as 17% and is fatal in about 10% of cases. Obtain a baseline chest X-ray and pulmonary-function tests, including diffusion capacity, when Pacerone therapy is initiated. Repeat history, physical exam, and chest X-ray every 3 to 6 months or if symptoms occur. Consider alternative antiarrhythmic therapy if the patient experiences signs or symptoms of pulmonary toxicity. Prednisone 40 to 60 mg/day tapered over several weeks may be helpful in treating pulmonary toxicity. Adult Respiratory Distress Syndrome (ARDS) Postoperatively, occurrences of ARDS have been reported in patients receiving amiodarone hydrochloride therapy who have undergone either cardiac or noncardiac surgery. Although patients usually respond well to vigorous respiratory therapy, in rare instances the outcome has been fatal. 5.3 Hepatic Injury Asymptomatic elevations of hepatic enzyme levels are seen frequently, but Pacerone can cause life-threatening hepatic injury. Histology has resembled that of alcoholic hepatitis or cirrhosis. Obtain baseline and periodic liver transaminases. If transaminases exceed three times normal, or doubles in a patient with an elevated baseline, discontinue or reduce dose of Pacerone, obtain follow-up tests and treat appropriately. 5.4 Worsened Arrhythmia Pacerone can exacerbate the presenting arrhythmia in about 2% to 5% of patients or cause new ventricular fibrillation, incessant ventricular tachycardia, increased resistance to cardioversion, and polymorphic ventricular tachycardia associated with QTc prolongation (Torsade de Pointes [TdP]). Correct hypokalemia, hypomagnesemia, and hypocalcemia before initiating treatment with amiodarone hydrochloride, as these disorders can exaggerate the degree of QTc prolongation and increase the potential for TdP. Give special attention to electrolyte and acid-base balance in patients experiencing severe or prolonged diarrhea or receiving drugs affecting electrolyte levels, such as diuretics, laxatives, systemic corticosteroids, or amphotericin B. 5.5 Visual Impairment and Loss of Vision Optic Neuropathy and Optic Neuritis Cases of optic neuropathy and optic neuritis, usually resulting in visual impairment and sometimes permanent blindness, have been reported in patients treated with amiodarone and may occur at any time during therapy. If symptoms of visual impairment appear, such as changes in visual acuity and decreases in peripheral vision, consider discontinuing Pacerone and promptly refer for ophthalmic examination. Regular ophthalmic examination, including funduscopy and slit-lamp examination, is recommended during administration of Pacerone [see Adverse Reactions (6.1) ] . Corneal Microdeposits Corneal microdeposits appear in the majority of adults treated with amiodarone hydrochloride. They are usually discernible only by slit-lamp examination but give rise

4 CONTRAINDICATIONS Cardiogenic shock. Sick sinus syndrome, second- or third-degree atrioventricular block, bradycardia leading to syncope without a functioning pacemaker. Known hypersensitivity to the drug or to any of its components, including iodine. Pacerone is contraindicated in patients with ( 4 ): Cardiogenic shock. Sick sinus syndrome, second- or third-degree AV block, bradycardia leading to syncope without a functioning pacemaker. Known hypersensitivity to the drug or any of its components.

10 OVERDOSAGE There have been cases, some fatal, of amiodarone hydrochloride overdose. Monitor the patient's cardiac rhythm and blood pressure, and, if bradycardia ensues, a β-adrenergic agonist or a pacemaker may be used. Treat hypotension with inadequate tissue perfusion with positive inotropic and vasopressor agents. Neither Pacerone nor its metabolite is dialyzable.