Expansion
Lungs, liver, thyroid, eyes, skin and nerves
Expansion
Toxicity by organ
- Lungs: pulmonary fibrosis and pneumonitis, the most feared
- Liver: hepatitis, deranged transaminases
- Thyroid: both hypo- and hyperthyroidism, because the molecule contains iodine
- Eyes: corneal microdeposits, almost universal, usually asymptomatic and reversible; optic neuropathy is rare but serious
- Skin: photosensitivity and a slate grey discolouration
- Nerves: peripheral neuropathy
- Heart: bradycardia, heart block, QT prolongation
Monitoring
- Before starting: thyroid function, liver function, urea and electrolytes, chest radiograph, and lung function tests where feasible
- Every 6 months: thyroid and liver function
- Annually: chest radiograph
- Ophthalmology review if visual symptoms develop
“Half life of 50 days” governs everything else: it takes months to reach steady state, which is why loading is needed; interactions and toxicity persist for months after stopping; and thyroid dysfunction can appear long after discontinuation.
Interactions: it inhibits CYP enzymes and P-glycoprotein, so it raises digoxin levels (halve the digoxin dose), potentiates warfarin, and adds to the QT prolongation of many drugs.
Amiodarone induced thyrotoxicosis has two types: type 1 in pre-existing thyroid disease, treated with carbimazole; type 2, a destructive thyroiditis, treated with steroids.