Inappropiate ADH secretion associated with massive vincristine overdosage.

A patient with acute lymphocytic leukemia is described who developed meningeal leukemia 14 months after the initial diagnosis was made. As part of his antileukemic therapy, at that time, he received prednisone and vincristine, given prophylactically to maintain a bone marrow remission. He inadvertently received 15 mg of vincristine instead of 1.5 mg. Following this overdosage he developed pancytopaenia, mild neurotoxicity and subsequently a grand mal seizure associated with the delayed onset of hyponatremia. This was presumed to be due to the inappropriate secretion of antidiuretic hormone (ADH) secondary to vincristine toxicity. This responded to fluid restriction and anti-epileptiform therapy.