Amiodarone HCl (Page 2 of 6)

5.6 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. Amiodarone hydrochloride-induced hyperthyroidism may be followed by a transient period of hypothyroidism.

Hypothyroidism may be primary or subsequent to resolution of preceding amiodarone hydrochloride- 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 amiodarone hydrochloride and thyroid hormone supplementation.

5.7 Bradycardia

Amiodarone hydrochloride 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 [see Drug Interactions ( 7)]. Bradycardia may require a pacemaker for rate control.

Postmarketing 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 hydrochloride when starting antiviral treatment [see Drug Interactions ( 7)].

5.8 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.

5.9 Fetal Toxicity

Amiodarone hydrochloride 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 [see Use in Specific Populations ( 8.1)].

5.10 Peripheral Neuropathy

Chronic administration of amiodarone hydrochloride may lead to peripheral neuropathy, which may not resolve when amiodarone is discontinued.

5.11 Photosensitivity and Skin Discoloration

Amiodarone hydrochloride 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.

5.12 Surgery

Volatile Anesthetic Agents

Patients on amiodarone hydrochloride therapy may be more sensitive to the myocardial depressant and conduction effects of halogenated inhalational anesthetics.

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)]

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 Postmarketing 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 organizing pneumonia, pulmonary alveolar hemorrhage, pleural effusion, pleuritis.

Gastrointestinal: pancreatitis, acute pancreatitis.

Hepatic: hepatitis, cholestatic hepatitis, cirrhosis.

Skin and Subcutaneous Tissue Disorders: urticaria, toxic epidermal necrolysis (sometimes fatal), erythema multiforme, Stevens-Johnson syndrome, exfoliative dermatitis, bullous dermatitis, drug rash with eosinophilia and systemic symptoms (DRESS), eczema, pruritus, skin cancer, lupus-like syndrome.

Musculoskeletal: myopathy, muscle weakness, rhabdomyolysis. Renal: renal impairment, renal insufficiency, acute renal failure. Reproductive: epididymitis, impotence.

Body as a whole: fever, dry mouth.

Endocrine and metabolic: thyroid nodules/thyroid cancer, syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Vascular: vasculitis.

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