Phenytoin toxicity and thyroid dysfunction.
A 48-year-old woman with known epilepsy presented to the Emergency Department with a 1-day history of decreasing coordination, impaired speech, and recurrent falls. Phenytoin levels were measured and found to be grossly elevated at 170 mmol/L. A diagnosis of phenytoin toxicity was made and she was treated by withdrawing the medication. During admission she was found to be profoundly hypothyroid despite being on adequate thyroid replacement therapy. Normalisation of phenytoin levels was associated with return of euthyroidism. The interaction between phenytoin, thyroid function, and thyroid replacement therapy is discussed.
Department of Emergency Medicine, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand. tobias.betteridge@cdhb.govt.nz
Tobias
T
Betteridge
John
J
Fink
D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D004827:Epilepsy / Q000188:drug therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced* / Q000188:drug therapy; D008875:Middle Aged; D010672:Phenytoin / Q000009:adverse effects* / Q000627:therapeutic use; D013974:Thyroxine / Q000627:therapeutic use
D000927:Anticonvulsants; D010672:Phenytoin; D013974:Thyroxine