Massive thyroxine intoxication: evaluation of plasma extraction

Abstract

Six patients were admitted after erroneous massive intake of levothyroxine (70–1200mg over an interval of 2–12 days). All patients developed classical symptoms of thyrotoxicosis within 3 days of the first dose; five patients presented grade II–III coma and one became stuporous (days 7–10). Two patients developed left ventricular failure and three had arrhythmias (days 8–11). Total thyroid hormone levels in serum on admission ranged 935–7728 nmol/l for T₄ (TT₄) and 23–399 nmol/l for T₃ (TT₃). All patients received treatment with hydrocortisone and Propranolol. Propylthiouracil was also given in 3 cases. Extractive techniques (charcoal haemoperfusion and/or plasmapheresis) were initiated 8–14 days after the first dose of L-T₄. The plasma disappearance rate (K) of TT₄ with plasmapheresis was 30 times higher, on average, than under standard medical treatment (M). Also, K of TT₄ under haemoperfusion was about five times higher than K under M. K changes for TT₃ were higher under haemoperfusion than under plasmapheresis. Furthermore, extractive procedures shortened the average half life of TT₄, (from 106.5±44.6 to 59.7±20.2 h, p<0.05).