*Amiodarone is an iodine containing long acting antiarrythmic drug which belongs to class III.
*Mechanism of action : It prolongs actional potential duration and effective refractory period is also prolonged. Conduction is slowed. When the drug is given through oral route, it has minimal effect on cardiac contractility and BP. Amiodarone is categorized as a class III antiarrhythmic agent, and prolongs phase 3 of the cardiac action potential. It has numerous other effects however, including actions that are similar to those of antiarrhythmic classes Ia, II, and IV. Amiodarone shows beta blocker-like and potassium channel blocker-like actions on the SA and AV nodes, increases the refractory period via sodium- and potassium-channel effects, and slows intra-cardiac conduction of the cardiac action potential, via sodium-channel effects.
Amiodarone resembles thyroid hormone, and its binding to the nuclear thyroid receptor might contribute to some of its pharmacologic and toxic action
*Uses : It is used in resistant cases of VT and recurrent VF. It is used in resistant cases of AF when other drugs have failed.
*ADVERSE EFFECTS :
- It interferes with thyroid function : Both hypothyroidism and hyperthyroidism may be seen. It inhibits peripheral conversion of T4 to T3.
- Cardiac depressant action : This is seen on IV injection but not on oral dose. On IV administration fall in BP and myocardial depression occurs.
- Peripheral neuropathy
- Pulmonary alveolitis and fibrosis
- Photosensitization
- Corneal microdeposits.
