Antidiuretic effect of desmopressin given in hemostatic dosages to healthy volunteers.

The aim of this study was to characterize the magnitude and duration of the antidiuretic effects elicited by desmopressin given in hemostatic dosage intravenously (i.v.) (0.3 microg/kg) or intranasally (i.n.) (300 microg) both as single or repeated doses (four i.n. doses with 12-hr intervals) to healthy volunteers. Urine osmolality increased to a maximum median value of 1,087 mOsmol/kg after the single i.v. dose, 1,065 after the single i.n. dose, and 1,071 during the repeated i.n. dosing schedule, and did not differ significantly between the three dosage schedules. The increase lasted for 24 hr after single doses, and 12 hr after the last of the repeated i.n. doses. Serum sodium did not decrease more than normal diurnal variation after single doses, but decreased marginally below the normal reference range in three volunteers after repeated doses. Lowest median serum sodium concentrations after single i.v. and i.n. doses were 140 and 141 mmol/l, respectively, and 139 after repeated i.n. doses. Body weight changed only marginally after single doses, but increased 1.3 kg during repeated dosing. In adult healthy volunteers, single desmopressin doses give an antidiuretic effect lasting for about 24 hr. There is no difference in magnitude or duration between i.v. or i.n. doses. The effect is prolonged as long as the doses are repeated. Serum sodium is only marginally affected by single doses, but tends to decrease after four repeated doses with 12-hr intervals. If desmopressin is repeated for a period of up to 48 hr, fluid intake should be restricted to 2 liters per day in adults.