Long-term treatment of the syndrome of inappropriate antidiuretic hormone secretion with phenytoin.

A 68-year-old patient with the syndrome of inappropriate antidiuretic hormone secretion secondary to basilary skull fracture was treated successfully with demeclocycline and phenytoin. Phenytoin, which was considered in the past only as a useful diagnostic tool, was given to the patient on a long-term basis. The drug reversed the patient's symptoms and abnormal laboratory values to normal limits without adverse reactions during a treatment period of 8 months.