Pacerone (amiodarone hydrochloride tablets, USP) are an antiarrhythmic drug, available for oral administration as 100 mg; peach tablets, 200 mg; pink tablets and 400 mg; white tablets containing amiodarone hydrochloride, USP. All three strengths of Pacerone tablets contain the following inactive ingredients: lactose monohydrate, magnesium stearate, povidone, pregelatinized corn starch, sodium starch glycolate and stearic acid. The 200 mg tablets also contain FD&C Red No. 40 and FD&C Yellow No. 6. The 100 mg tablets also contain FD&C Yellow No. 6. Amiodarone hydrochloride, USP is a benzofuran derivative: 2-butyl-3-benzofuranyl 4-[2-(diethylamino)-ethoxy]-3,5-diiodophenyl ketone hydrochloride. The structural formula is as follows: C 25 H 29 I 2 NO 3 ∙ HCl Molecular Weight: 681.8 C 25 H 29 I 2 NO 3 ∙ HCl Molecular Weight: 681.8 Amiodarone hydrochloride, USP is a white to cream-colored crystalline powder. It is slightly soluble in water, soluble in alcohol, and freely soluble in chloroform. It contains 37.3% iodine by weight. Meets USP Dissolution Test 4. Chemical Structure

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. Recurrent hemodynamically unstable ventricular tachycardia.

Pacerone tablets, 100 mg, are peach, round, flat-faced, uncoated tablets, debossed with "P" on one side, and "U-S" above "144" on the other side. Pacerone tablets, 200 mg, are pink, round, flat-faced, scored, uncoated tablets, debossed with "P 200 " on the unscored side, and "U-S" above and "0147" below the score on the reverse side. Pacerone tablets, 400 mg, are white to off-white, round, uncoated, scored tablets, debossed with "U-S' above and "1645' below the score on one side and "P 400 " on the unscored side. Tablets: 100 mg, 200 mg and 400 mg

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. 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 . 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.

Persistence of Adverse Effects: Adverse reactions and drug interaction can persist for several weeks following discontinuation. Impaired Vision: Corneal microdeposits (common; reversible), optic neuropathy/neuritis (rare; may lead to blindness). Thyroid Abnormalities: Hyperthyroidism or hypothyroidism. 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

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

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

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

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 . 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 to symptoms such as visual halos or blurred vision in as many as 10% of patients. Corneal microdeposits are reversible upon reduction of dose or termination of treatment. Asymptomatic microdeposits alone are not a reason to reduce dose or discontinue treatment

Thyroid Abnormalities Amiodarone hydrochloride inhibits peripheral conversion of thyroxine (T 4 ) to triiodothyronine (T 3 ) and may cause increased thyroxine levels, decreased T 3 levels, and increased levels of inactive reverse T 3 (rT 3 ) in clinically euthyroid patients. Amiodarone hydrochloride can cause either hypothyroidism (reported in up to 10% of patients) or hyperthyroidism (occurring in about 2% of patients). Monitor thyroid function prior to treatment and periodically thereafter, particularly in elderly patients, and in any patient with a history of thyroid nodules, goiter, or other thyroid dysfunction. Hyperthyroidism may induce arrhythmia breakthrough. If any new signs of arrhythmia appear, the possibility of hyperthyroidism should be considered. Antithyroid drugs, β-adrenergic blockers, temporary corticosteroid therapy may be necessary to treat the symptoms of hyperthyroidism. The action of antithyroid drugs may be delayed in amiodarone-induced thyrotoxicosis because of substantial quantities of preformed thyroid hormones stored in the gland. Radioactive iodine therapy is contraindicated because of the low radioiodine uptake associated with amiodarone-induced hyperthyroidism. Pacerone-induced hyperthyroidism may be followed by a transient period of hypothyroidism. Hypothyroidism may be primary or subsequent to resolution of preceding amiodarone-induced hyperthyroidism. Severe hypothyroidism and myxedema coma, sometimes fatal, have been reported in association with amiodarone therapy. In some clinically hypothyroid amiodarone-treated patients, free thyroxine index values may be normal. Manage hypothyroidism by reducing the dose of or discontinuing Pacerone and thyroid hormone supplementation

Bradycardia Pacerone causes symptomatic bradycardia or sinus arrest with suppression of escape foci in 2% to 4% of patients. The risk is increased by electrolytic disorders or use of concomitant antiarrhythmics or negative chronotropes . Bradycardia may require a pacemaker for rate control. Post-marketing cases of symptomatic bradycardia, some requiring pacemaker insertion and at least one fatal, have been reported when ledipasvir/sofosbuvir or sofosbuvir with simeprevir were initiated in patients on amiodarone. Bradycardia generally occurred within hours to days, but in some cases presented up to 2 weeks after initiating antiviral treatment. Bradycardia generally resolved after discontinuation of antiviral treatment. The mechanism for this effect is unknown. Monitor heart rate in patients taking or recently discontinuing amiodarone when starting antiviral treatment

Implantable Cardiac Devices In patients with implanted defibrillators or pacemakers, chronic administration of antiarrhythmic drugs may affect pacing or defibrillation thresholds. Therefore, at the inception of and during amiodarone treatment, pacing and defibrillation thresholds should be assessed

Fetal Toxicity Pacerone may cause fetal harm when administered to a pregnant woman. Fetal exposure may increase the potential for cardiac, thyroid, neurodevelopmental, neurological, and growth effects in neonate

Peripheral Neuropathy Chronic administration of Pacerone may lead to peripheral neuropathy, which may not resolve when Pacerone is discontinued

Photosensitivity and Skin Discoloration Pacerone induces photosensitization in about 10% of patients; some protection may be afforded sun-barrier creams or protective clothing. During long-term treatment, a blue-gray discoloration of the exposed skin may occur. The risk may be increased in patients of fair complexion or those with excessive sun exposure. Some reversal of discoloration may occur upon drug discontinuation

Surgery Volatile Anesthetic Agents Patients on Pacerone therapy may be more sensitive to the myocardial depressant and conduction effects of halogenated inhalational anesthetics.

Because of amiodarone's long half-life, expect drug interactions to persist for weeks to months after discontinuation of amiodarone. Drug interactions with amiodarone are described in Table 1 below. Table 1: Amiodarone Drug Interactions Concomitant Drug Class/Name Examples Clinical Comment Pharmacodynamic Interactions 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. Pharmacokinetic Interactions CYP450 Inhibitors grapefruit juice, certain fluoroquinolone and macrolide antibiotics, azole antifungals, cimetidine, certain protease inhibitors 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 CYP3A4 substrates may be required. Warfarin Potentiates anticoagulant response and can result in serious or fatal bleeding. Coadministration increases prothrombin time by 100% after 3 to 4 days. Reduce warfarin dose by one-third to one-half and monitor prothrombin times. Phenytoin Increased steady-state levels of phenytoin. Monitor phenytoin levels. Hepatitis C Direct Acting Antiviral sofosbuvir Cases of symptomatic bradyarrhythmia requiring pacemaker insertion have been reported in patients on oral maintenance amiodarone who initiated therapy with sofosbuvir. CYP3A Substrate lidocaine Sinus bradycardia has been reported with oral amiodarone in combination with lidocaine given for local anesthesia. Monitor heart rate. A lower starting dose of lidocaine may be required. CYP3A Substrate fentanyl Fentanyl in combination with amiodarone may cause hypotension, bradycardia, and decreased cardiac output. Avoid coadministration of amiodarone with other antiarrhythmics and drugs known to prolong the QT interval. Amiodarone is a substrate for CYP3A and CYP2C8, so inhibitors and inducers affect amiodarone exposure. Amiodarone inhibits P-glycoprotein and CYP1A2, CYP2C9, CYP2D6, and CYP3A, increasing exposure to other drugs.