Osmoregulation and desmopressin pharmacokinetics in enuretic children

Objective. The aim was to compare responders and nonresponders to antienuretic treatment with desmopressin with respect to pharmacokinetics and renal effects of the drug. Methods. Twelve children, aged 7.6 to 16.2 years, with nocturnal enuresis were examined. Six patients were nonresponders and 6 were responders to desmopressin treatment. The children were given 2 mg of desmopressin intravenously and plasma concentrations of the drug were monitored overnight. Urine parameters were followed for 24 hours after desmopressin administration. Ten patients also underwent a thirst provocation test. Results. Desmopressin pharmacokinetics did not differ between the groups. Neither nocturnal urine production nor morning urine osmolality after desmopressin injection differed between responders and nonresponders, whereas the responders produced significantly larger amounts of significantly less concentrated urine during the day after the injection compared with the nonresponders (urine production, 2.02 +/- 0.84 and 0.77 +/- 0.20 mL/kg/h; urine osmolality, 558 +/- 271 and 883 +/- 134 mOsm/kg). Nonresponders voided with smaller bladder volumes (2.43 +/- 0.68 mL/kg body weight) than responders (4.70 +/- 1.21 mL/kg). The responders produced significantly less concentrated urine than the nonresponders during the thirst provocation test (607 +/- 185 and 922 +/- 217 mOsm/kg, respectively). Conclusion. Intravenous desmopressin pharmacokinetics and desmopressin renal effects did not differ between responders and nonresponders to desmopressin treatment. Nonresponders had a smaller spontaneous bladder capacity and responders produced less concentrated urine.