Amiodarone

Amiodarone touches nearly every organ system — thyroid, lungs, liver, eyes, skin. The arrhythmia may kill fast, but the drug's toxicities accumulate slowly and can be just as dangerous.

Amiodarone is a class III antiarrhythmic that prolongs the action potential and refractory period by blocking potassium channels, but it also blocks sodium, calcium, and beta-adrenergic receptors — making it uniquely broad-spectrum. It treats life-threatening ventricular tachycardia (VT), ventricular fibrillation (VF), and refractory atrial fibrillation. Its half-life is extraordinarily long — 40 to 55 days — meaning drug effects and toxicities persist weeks after discontinuation. IV loading doses are given through a central line when possible because peripheral infusion causes severe phlebitis; an inline filter is required. Oral maintenance follows. Baseline and ongoing monitoring includes pulmonary function tests (pulmonary fibrosis is potentially fatal), thyroid function (TSH — the drug contains iodine and can cause hypo- or hyperthyroidism), liver function tests (hepatotoxicity), and annual ophthalmologic exams (corneal microdeposits, optic neuropathy). The QT interval must be monitored continuously during IV infusion because excessive prolongation leads to torsades de pointes. Photosensitivity and blue-gray skin discoloration develop with long-term use; patients need sunscreen and protective clothing. Amiodarone dramatically increases digoxin and warfarin levels — doses of both must be reduced, often by half.

Key Distinctions

Don't confuse amiodarone's broad multi-channel blockade with adenosine's brief AV-node blockade — adenosine is for SVT and lasts seconds; amiodarone treats VT/VF and lasts weeks. Students forget that pulmonary toxicity (dry cough, dyspnea, crackles) mimics heart failure — always suspect the drug. Hypo- and hyperthyroidism are both possible because amiodarone contains ~37% iodine by weight.

Clinical Pearl

Think 'amiodarone touches everything': lungs, thyroid, liver, eyes, skin, QT interval. If a long-term amiodarone patient develops a new cough — think lungs first, not infection.