Also possesses electrophysiologic characteristics of all 4 Vaughan Williams classes.
Like Class I drugs, amiodarone blocks sodium channels at rapid pacing frequencies.
Like class II drugs, it exerts antisympathetic activity through beta-adrenoreceptor (weak) antagonism.
Class II type effects: negative chronotropic effect in nodal tissues.
Class III effect: lengthens the cardiac action potential.
In addition to blocking sodium channels, amiodarone blocks myocardial potassium channels, which contributes to slowing of conduction and prolongation of refractoriness.
Antisympathetic action and block of calcium and potassium channels are responsible for the negative dromotropic effects on the sinus node and for the slowing of conduction and prolongation of refractoriness in the atrioventricular (AV) node.
Onset - Minutes when used as bolus in V.Fib/pulseless VT
Peak - 10-15 minutes
Duration - amiodarone has a prolonged duration of action and if used for rhythm control for other than arrest situations has a slow onset of action (1 - 2 hours)