Amiodarone - a 'broad spectrum' antiarrhythmic drug

Amiodarone, an iodinated benzofuran derivative, introduced in 1960's as an anti-anginal agent, emerged as a potent anti-arrhythmic agent by 1970's and is currently one of the most commonly prescribed drugs in US for ventricular and atrial arrhythmias. Although amiodarone is considered a class III anti-arrhythmic agent, it also has class I, II, IV actions, making it a unique and effective anti-arrhythmic agent. Because of its minimal negative inotropic activity and very low rate of pro-arrhythmia, it is considered safe in treating arrhythmias in patients with Coronary Artery Disease and Left ventricular systolic dysfunction. Despite these advantages, long term oral therapy with amiodarone is limited by side effect profile involving various organs like thyroid, lung, heart, liver, skin etc. Though the side effects can be decreased significantly by keeping the maintenance dose at 200 to 300 mg/day, patients on amiodarone should be followed closely. Amiodarone interacts with medications such as Warfarin, Digoxin, Macrolides, Floroquinolones etc., which share Cytochrome P450 metabolic pathway. Hence reducing their doses prior to starting amiodarone is recommended. Amiodarone, a category D drug, is contraindicated in pregnant and breast feeding women. This review discusses the pharmacokinetics of amiodarone, its evolving clinical indications, management of toxicity and drug interactions.