Amiodarone – class IIIa

Amiodarone – class IIIa

Amiodarone is designated as class IIIa antiarrhythmic agent in the Modernized Classification of Cardiac Antiarrhythmic Drugs [1]. This is the group of voltage dependent K+ channel blockers. It is a nonselective K+ channel blocker. Another drug in class IIIa is dronedarone, which is a related drug free of iodine atoms and hence the thyroid related adverse effects of amiodarone.

Amiodarone is useful in wide range of atrial and ventricular arrhythmias and it is a so called broad spectrum antiarrhythmic agent and widely used.

Amiodarone prolongs QTc, but torsades des pointes is rare, possibly due to its effects on other channels like beta blocking and calcium channel blocking effects. That is why earlier it was called as a class 10 antiarrhythmic agent in jest, with actions of classes I, II, III and IV.

It may be noted that amiodarone was originally introduced as an antianginal agent and its antiarrhythmic potential was noted later.

Hypotension common with intravenous amiodarone is due to excipients like polysorbate and benzyl alcohol. A newer formulation which contains cyclodextrin and devoid of these excipients was found to be better on this aspect, requiring statistically lower number of fluid boluses to prevent hypotension (P = 0.001) [2].

References

1. Ming Lei, Lin Wu, Derek A Terrar, Christopher L-H Huang. Modernized Classification of Cardiac Antiarrhythmic Drugs. Circulation. 2018 Oct 23;138(17):1879-1896.
2. Desirae E Lindquist, A Shaun Rowe, Eric Heidel, Travis Fleming, John R Yates. Evaluation of the Hemodynamic Effects of Intravenous Amiodarone Formulations During the Maintenance Phase Infusion. Ann Pharmacother. 2015 Dec;49(12):1317-21.