Effect of carbamazepine on plasma and urine arginine-vasopressin.

1. Five normal subjects were studied before and during treatment with carbamazepine. 2. Plasma sodium, plasma and urine arginine-vasopressin and urine osmolality were measured during a day of water deprivation, before and during drug treatment. 3. During treatment with carbamazepine plasma sodium increased wheras plasma and urine arginine-vasopressin and urine osmolality decreased. Plasma and urine arginine-vasopressin were signifi"antly correlated with urine osmolality. However, carbamazepine did not affect the osmolality of urine produced by the kidney, in response to endogenous arginine-vasopressin. 4. Plasma and urine arginine-vasopressin were significantly correlated with plasma sodium on both control and drug-treatment days, but the relationships of plasma and urine arginine-vasopressin to plasma sodium were different during carbamazepine treatment, as compared with the control period. 5. It is suggested that the threshold of the hypothalamic osmoreceptors for release of arginine-vasopressin is modified by carbamazepine, and that this may be either a direct action or secondary to another action of the drug.