Anaesthetics, general + Levothyroxine - Drug Interactions

Clinical evidence,mechanism, importance and management

Two patients taking levothyroxine developed severe hypertension (240/140 and 210/130 mmHg,respectively) and tachycardia (190 and 150 bpm) when they were given ketamine. Both were effectively treated with 1mg of intravenous propranolol (See reference number 1). It was not clear whether this was an interaction or simply a particularly exaggerated response to ketamine,but care is clearly needed if ketamine is given to patients taking thyroid replacement.

1. Kaplan JA,Cooperman LH. Alarming reactions to ketamine in patients taking thyroid medication — treatment with propranolol. Anesthesiology (1971) 35, 229–30.