Severe symptoms following a massive intentional L-thyroxine ingestion

L-Thyroxine (T-4) is commonly prescribed medication for hypothyroidism in h umans and animals. Overdose has generally resulted in limited symptomatolog y managed with sedatives and beta-adrenergic receptor antagonists. We descr ibe the largest acute T4 ingestion eve; reported, which resulted in a profo und thyrotoxicosis, resistant to treatment. A 34-y-old man ingested 900 (0. 8 mg) tablets of veterinary T-4 (720 mg) and was given 60 g of activated ch arcoal. He became lethargic on post-ingestion days 2 and 3; had vomiting, d iaphoresis and insomnia on day 4; on day 5 he "looked like he had too much coffee", began "using a lot of words" and became agitated, assaultive and s topped speaking intelligibly; and on day 6 returned to the hospital combati ve and confused. He was diaphoretic, mydriatic, hyperreflexic, tremulous, w ith clear lungs and active bowel sounds, and received activated charcoal, h aloperidol, diazepam, and phenobarbital, and was tracheally intubated. Duri ng hospitalization he was rehydrated, treated with propranolol and diazepam , but remained continuously tachycardic. On day 12 he became afebrile and h is tachycardia resolved. Free T-4 levels ranged from > 13 mcg/dL on day 6 t o 1.2 mcg/dL on day 12. By discharge (day 15) he had lost 20 kilograms of b ody weight, but was clinically euthyroid 2 w later. This case suggests that large intentional T-4 ingestions should be managed differently than curren t T-4 overdose protocol.