1-desamino-8-D-arginine vasopressin (DDAVP) concentration test

Classical dehydration and vasopressin tests for estimation of renal concentrating capacity are inconvenient and sometimes hazardous. We attempted to use the new potent long-lasting synthetic vasopressin analogue (DDAVP) which has no side effects for testing renal concentrating capacity in adults. Four groups of persons were investigated: in Groups 1 and 3, 11 and another 11 healthy subjects; in Group 2, seven convalescent older patients; and in Group 4, 11 patients with pituitary diabetes insipidus (DI). Groups 1 and 2 were investigated during 15 hours' dehydration; DDAVP was given at the end of the 12th hour intravenously (4 microgram) or intransally (80 micron). DDAVP failed to influence strikingly the normal increase in renal concentration induced by lengthening the dehydration from 12 hours to 15 hours. On the other hand, in patients with DI under prolonged treatment as well as in healthy individuals (Group 3), a dose of 20 to 40 microgram of DDAVP administered intranasally induced (at least) as high peak urine osmolality during ad libitum fluid intake as was induced in normal subjects (Group 1) by 12 hours' dehydration alone. In patients with DI the maximal effect of DDAVP obtained during ad libitum fluid intake could be further enhanced by added dehydration. Urine sampling for osmolality three hours after a single intranasal dose of 40 microgram DDAVP during ad libitum fluid intake is a new safe, simple and convenient test for rapid estimation of concentrating ability.