[Lobenzarit disodium (CCA)--induced diabetes insipidus in a patient with rheumatoid arthritis]

A 44-year-old female with 16-year history of rheumatoid arthritis visited Akiru Hospital with complaints of a thirst, a dry mouth and a general fatigue. One week prior to admission, the patient manifested excessive thirsty feeling, a body weight loss and a sleepless by the polyuria. She has been given 5-10 mg of prednisolone and 240 mg of lobenzarit disodium (CCA) in a day for 11 months. A hematologic examination showed no abnormality, and the examination of her serum showed the following values: BUN, 9.3 mg/dl; creatinine, 0.9 mg/dl; sodium, 139 mEq/l; chloride, 102 mEq/l; potassium, 3.9 mEq/l; osmolality, 290 mOsm/l. Plasma antidiuretic hormone (ADH) level increased slightly (6.0 pg/ml). Examination of her urine revealed specific gravity, 1.005; no trace of glucose, protein, blood and ketones; normal sediment; and osmolality, 209 mOsm/l. The patient was given exogenous ADH (10 units of vasopressin tannate in oil, intramuscularly) to obtain a diagnosis, and she was found to be unable to concentrate her urine more than 1.008 in the specific gravity. A water restriction, as a test for diabetes insipidus, also failed to concentrate her urine in the specific gravity and in the osmolality. Together with these findings, the patient was diagnosed to be a diabetes insipidus, and CCA was seemed to account for the disease. This unfavorable effect of CCA appeared to be reversible, since the patient recovered her urinary concentrating ability after the medication of CCA was discontinued.