Objective: The purpose of this trial was to investigate whether a renal concentrating capacity test with desmopressin could be performed with oral tablets instead of the previously used nasal spray.
Material and methods: A total of 154 children aged 3-18 years, who were candidates for a renal concentrating capacity test, were included in a randomized, double-dummy, crossover trial. The patients performed four tests: desmopressin tablets 0.6 mg (twice); desmopressin nasal spray 20 microg; and placebo.
Results: A total of 118 patients qualified for the primary analysis. The mean osmolality was 978 mOsm/kg after nasal spray, 934 mOsm/kg after the tablet tests and 721 mOsm/kg after placebo. Desmopressin tablets were non-inferior to intranasal spray (lower 97.5% one-sided confidence limit= -67 mOsm/kg; non-inferiority limit= -69 mOsm/kg). The tablet test was reproducible and the within-patient SD between the two tablet tests was 111 mOsm/kg. Desmopressin tablets and spray produced a significantly higher urine osmolality compared to placebo (p<0.001). Eighteen patients reported a total of 25 adverse events, three of which occurred on placebo. Six events in four patients were judged as treatment-related, and all of these comprised either headache or abdominal pain. No serious adverse events were reported.
Conclusion: Desmopressin intranasal spray (20 microg) can be exchanged for desmopressin tablets (0.6 mg) in the assessment of renal concentrating capacity in children.