Amiodarone is a class III antiarrhythmic drug used for treating ventricular arrythmias. It is administered orally or intravenously. Amiodarone targets the cardiac myocytes where it blocks the inward rectifying potassium channels. This potassium is responsible for phase 3 of the action potential. During phase 3, K+ goes out of the cell to allow repolarization. In the presence of amiodarone, K+ accumulates in the cell since the potassium channels are blocked by amiodarone. This causes the repolarization phase, and thus, the action potential duration to be prolonged. The excitability of the cell is reduced and this leads to a slowing of the heart rate. The QRS duration is increased and the QT interval is also prolonged. These effects on the action potentials and the heart rate therefore mean that abnormal heart rhythms like tachyarrhythmias are less likely to occur. Amiodarone may have adverse effects such as thyrotoxicosis or hypothyroidism, tremor, uncontrollable and unusual movement of the body, dizziness, headache, nausea and vomiting, constipation, blurred vision, due to its effects on other targets such as beta-adrenergic receptors, sodium channels, and calcium channels.

Amiodarone Pathway (New) References