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Amiodarone Overview

Homepage: EMNote.org ■ 🚩Membership: https://tinyurl.com/joinemnote 🚩ACLS Lecture: https://tinyurl.com/emnoteacls Amiodarone Overview Mechanism of Action Amiodarone exerts multichannel blockade and non-competitive adrenergic inhibition: Potassium channel blockade: Prolongs phase 3 repolarization (class III effect), increasing myocardial refractory period. Sodium channel blockade: Slows conduction velocity (class Ia effect). Calcium channel blockade: Reduces intracellular calcium during contraction (class IV effect). β-/α-adrenergic receptor antagonism: Reduces sympathetic drive and heart rate. Thyroid hormone analog: Competes with nuclear thyroid receptors, contributing to both therapeutic and adverse effects. Brand Names Cordarone Pacerone Nexterone Indications FDA-Approved Recurrent ventricular fibrillation (VF) Hemodynamically unstable ventricular tachycardia (VT). Off-Label Atrial fibrillation (AFib) rhythm control Supraventricular tachycardia (SVT). Special Populations Elderly: Start at lower end of dosing range. Hepatic impairment: Monitor LFTs; discontinue if ALT/AST more than 3× ULN. Precautions & Contraindications Contraindications Cardiogenic shock 2nd/3rd-degree AV block or sinus node dysfunction without pacemaker Known hypersensitivity to iodine/amiodarone. Monitoring Requirements Pulmonary: Baseline CXR and PFTs; repeat every 3–6 months. Hepatic: LFTs at baseline and periodically. Thyroid: TSH every 6 months. Ocular: Annual slit-lamp exams. Adverse Effects Common Cardiovascular: Bradycardia, hypotension (20% with IV). Pulmonary: Cough, dyspnea, interstitial pneumonitis (risk: 1–17%). Endocrine: Hypothyroidism (6%), hyperthyroidism (3%). Dermatologic: Photosensitivity, blue-gray skin discoloration. Serious Hepatotoxicity: Elevated LFTs, hepatitis (monitor closely). Neuropathy: Peripheral neuropathy, ataxia. Ocular: Optic neuritis, corneal microdeposits (≥90% of long-term users). Drug Interactions QT-prolonging agents (e.g., fluoroquinolones, TCAs): ↑ Risk of torsades de pointes. Warfarin: ↑ INR due to CYP2C9 inhibition. Amiodarone’s long half-life (40–55 days) necessitates prolonged monitoring even after discontinuation. Clinicians should balance its efficacy against the risk of multiorgan toxicity, particularly in long-term use. Always initiate therapy in a monitored setting due to arrhythmia exacerbation risk.