Detection of renal impairment in cases of chronic abuse of analgesics by administration of desamino-D-arginine vasopressin

An early diagnosis of renal dysfunction is particularly important in patients with chronic abuse of analgesics. First morphological changes in cases of analgesic nephropathy are found in the renal medulla. Therefore, urinary osmolarity as well as the urinary excretion of cyclic adenosine monophosphate (AMP) and kallikrein were measured after application of desamino-D-arginine vasopressin (DDAVP) as parameters of the renal tubular function in 21 patients with normal creatinine clearance and a regular, excessive use of analgesics. The results were compared with those of 17 healthy volunteers and 8 patients with chronic renal insufficiency after analgesic nephropathy. In patients with analgesic nephropathy the urine osmolarity after 12 h of thirst was 367 +/- 28 mOsm/kg and did not increase after DDAVP. The results obtained from healthy volunteers were 781 +/- 39 mOsm/kg. Half of the patients with chronic misuse of analgesics had lower values of urine osmolarity after thirst and DDAVP compared to the reference area of healthy subjects. Similar results were found when the effect of DDAVP under conditions of water-loading was tested. The excretion of cyclic AMP as a second messenger of DDAVP and of kallikrein did not differ between patients with chronic abuse of analgesics and healthy volunteers. The excretion of kallikrein in patients with manifest analgesic nephropathy, however, was decreased. Thus the renal concentration test with DDAVP proved to be useful in early diagnosis of renal dysfunction caused by analgesics.