Amiodarone is a class III antiarrhythmic agent used in the treatment of atrial, nodal and ventricular tachycardias. The main mechanism of action is by blocking potassium channels which inhibits repolarisation and hence prolongs the action potential. Amiodarone also has other actions such as blocking sodium channels (a class I effect)

The use of amiodarone is limited by a number of factors

• very long half-life (20-100 days). For this reason, loading doses are frequently used
• should ideally be given into central veins (causes thrombophlebitis)
• has proarrhythmic effects due to lengthening of the QT interval
• interacts with drugs commonly used concurrently (p450 inhibitor) e.g. Decreases metabolism of warfarin
• numerous long-term adverse effects (see below)

Monitoring of patients taking amiodarone

• TFT, LFT, U&E, CXR prior to treatment
• TFT, LFT every 6 months

Adverse effects of amiodarone use

• thyroid dysfunction: both hypothyroidism and hyper-thyroidism
• corneal microdeposits (reversible)
• pulmonary fibrosis/pneumonitis, alveolitis → progress to fibrosis
• liver fibrosis/hepatitis
• peripheral neuropathy, myopathy
• photosensitivity
• 'slate-grey' appearance
• thrombophlebitis and injection site reactions
• bradycardia,