Massive vasopressin-resistant polyuria induced by dexamethasone

A case of severe polyuria elicited by intravenous administration of a normal pharmacological dose of dexamethasone is reported. The polyuria did not respond to treatment with vasopressin. A 15-year-old girl with a brain tumour was referred for surgery. After induction of anaesthesia she received dexamethasone 4 mg i.v., and developed a massive polyuria with hourly diuresis of up to 1250 ml. There was no response to treatment with vasopressin in doses well above those normally used. The patient did not fulfil any known cause of diabetes insipidus, and to our best knowledge, this case is the first with glucocorticoid-induced and vasopressin-resistant polyuria ever reported in man.