Amiodarone

Amiodarone is a powerful antiarrhythmic medication used to treat and prevent a range of serious heart rhythm disturbances, including ventricular fibrillation, ventricular tachycardia, and atrial fibrillation. It is one of the most effective antiarrhythmic drugs available but requires careful monitoring due to its complex side effect profile.

Amiodarone works through multiple mechanisms (it is a class III antiarrhythmic but has properties of all four Vaughan Williams classes). It prolongs the action potential and refractory period in cardiac muscle, slows conduction through the AV node, and blocks certain sodium and calcium channels. This combination of effects makes it effective across a wide range of arrhythmias but also contributes to its potential for toxicity.

Amiodarone may be given intravenously during resuscitation from VF or pulseless VT that has not responded to defibrillation. After cardiac arrest, oral amiodarone may be prescribed long-term to reduce the risk of recurrent VT/VF, particularly in patients who continue to have breakthrough arrhythmias despite an ICD.

Amiodarone contains iodine and can affect multiple organ systems with prolonged use. Important side effects include thyroid dysfunction (both hypothyroidism and hyperthyroidism can occur); pulmonary toxicity, which can cause breathlessness and lung damage; hepatotoxicity requiring liver function monitoring; corneal microdeposits (usually asymptomatic, with regular eye checks recommended); photosensitivity and a blue-grey skin discolouration with very long-term use; and peripheral neuropathy, sleep disturbance, and tremor. Regular monitoring of thyroid function, liver function, and lung function is required for all patients on long-term amiodarone.