Lengthening of the duration of action of DDAVP by "ineffective" doses of clofibrate in patients with pituitary diabetes insipidus.

Duration of action of single intravenous and intranasal doses of 1-Deamino-8D-Arginine Vasopressin (DDAVP) was lengthened by "ineffective" doses of clofibrate (not affecting water metabolism when administered alone) in patients with pituitary diabetes insipidus. This interaction was observed when as low doses as 0.02 mug DDAVP were administered intravenously to one patient and as high doses as 1 and 2 mug DDAVP were given intravenously to another patient. Administration of less or more DDAVP than "optimal" for the interaction resulted in decreased or absent potentiation by clofibrate. The exact cause of the interaction is unknown.