Amiodarone is an effective anti-arrhythmic medication which belongs to class III of the Vaughan-Williams classification.

The half life of amiodarone is long at 20 to 107 days – this means there is the potential for drug interactions to occur even months after treatment has stopped.

Multiple drug interactions may occur, including:
  • Warfarin – inhibits metabolism → enhanced anti-coagulant effect
  • TCA – avoid concurrent use as increased risk of ventricular arrhythmias 
  • Phenytoin – inhibits metabolism → increased plasma concentration 
  • Digoxin – increases plasma concentration; half digoxin dose 
  • Beta blockers – risk of AV block and ventricular arrhythmias 
  • Calcium channel blockers – risk of AV block 
  • Grapefruit juice – increases the plasma concentration of amiodarone 
  • Cimetidine – increases plasma concentration of amiodarone 

Amiodarone is also renowned for its side effects which include:
  • Slate-grey discoloration of the face
    • Occurs in 1-7%
  • Corneal microdeposits
    • reversible on stopping treatment
    • associated with night glare
    • found in nearly 100% of patients
  • Taste disturbance
  • Photosensitivity
  • Thyroid dysfunction (hyper and hypothyroidism)
    • Occurs as amiodarone contains iodine
    • If thyrotoxicosis occurs – should usually withdraw amiodarone at least temporarily
    • If hypothyroidism occurs amiodarone can be continued if it is essential
    • Between 2 and 12% of patients may develop thyrotoxicosis and between 6 to 13% develop hypothyroidism
  • Pulmonary toxicity
    • occurs in 5-10%
    • may be pulmonary fibrosis or interstitial pneumonitis
  • Arrhythmias
  • Hepatotoxicity
    • raised serum transaminases occur in 15-20%
  • Neurological side effects
    • Peripheral neuropathy
    • Tremor
    • Ataxia – very rarely
  • Alopecia – very rarely
  • Hypokalaemia
LFTs and TFTs should be done before commencing treatment and then every 6 months. A CXR should also be performed prior to commencing treatment. 

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Secret collector of interesting anonymised ECGs. Fan of the Bath Photomarathon. Lover of cream teas. [Sarah Hudson] (Your Picture)