Amiodarone Pharmacology

Master answer

Side Effects of Amiodarone:

Side effects reflect long elimination half-life and significant accumulation in tissues. Side affects increase when maintenance doses are above 400mg daily.

• Respiratory
  • Most serious is pneumonitis. Risk is 5-10% at 3 years with a mortality of 10% long term.
  • May be due to increased oxygen free radicals and risk increased by high FiO2
  • 2 phenotypes- slow insidious and acute onset
  • May be reversible if treatment stopped early
• Cardiac
  • Prolonged QTc with Torsade’s
  • Proarrhythmic (ventricular tachyarrhythmia)
  • Bradycardias resistant to atropine
  • Peripheral vasodilation leading to hypotension with decreased responsiveness to adrenergic stimuli
• Neurological
  • Peripheral neuropathy, tremor, sleep disturbance
  • Myopathy
• Endocrine
  • Both hyperthyroidism and hypothyroidism may occur (usually reversible)- 2-4% of patients
  • Prevents peripheral conversion of T4 to T3 (detected by increased plasma [TSH])
  • 37% of weight of Amiodarone is iodine, which may precipitate hyperthyroidism
  • Pre-existing thyroid disease increases risk
• GIT
  • Hepatitic dysfunction, LFT derangement and cirrhosis has been observed
  • Metallic taste during loading
• Ophthalmic
  • Corneal microdeposits but visual impairment less likely
  • Optic neuropathy (insidious onset, bilateral). Often reversible if discontinued
• Dermatological
  • Photosensitivity
  • Slate gray pallor of the face, continues after drug discontinuation
• Pregnancy and lactation
  • Avoid in from 3 months pre-pregnancy to after breast feeding has finished
  • May cause hypothyroidism and bradycardia in the fetus. Foetal hypothyroidism may lead to impairment of myelination
• Contraindicated in porphyria
• Miscellaneous
  • IV preparation is irritant and should be administered through a central vessel