Introduction

Amiodarone is a class III antiarrhythmic agent used in the treatment of atrial, nodal and ventricular tachycardias.

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 the lengthening of the QT interval
  • Interacts with drugs commonly used concurrently (p450 inhibitor) e.g. decreases the metabolism of warfarin
  • Numerous long-term adverse effects (see below)

Mechanism of action

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)

Adverse effects

  • Thyroid dysfunction: both hypothyroidism and hyper-thyroidism
  • Corneal deposits
  • Pulmonary fibrosis/pneumonitis
  • Liver fibrosis/hepatitis
  • Peripheral neuropathy, myopathy
  • Photosensitivity
  • 'slate-grey' appearance
  • Thrombophlebitis and injection site reactions
  • Bradycardia
  • Lengths QT interval

Monitoring

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