Pharmacokinetics and Pharmacodynamics of Desmopressin Oral Lyophilisate Formulation in the Paediatric Population

Inclusion Criteria: * Children with an uro- and/or nephropathy who need an urinary concentration test OR Children with monosymptomatic nocturnal enuresis (based on nocturnal polyuria) with treatment failure on desmopressin tablet * Otherwise healthy children (on medical history and physical examination) * Parents or legal guardian of the child signed the informed consent form * Age: between 6 months and 8 years * Minimum weight: 8 kg Exclusion Criteria: * Diabetes insipidus * Renal failure (eGFR\<60ml/min/1,73m²) * Current urinary tract infection * Syndrome of inappropriate antidiuretic hormone secretion * Heart failure * Clinical significant medical conditions (renal, hepatic, gastro-intestinal, pulmonary, cardiac, endocrinologic) that might interfere with the clinical endpoints * Sensitivity to desmopressin or excipients of the oral lyophilisate formulation * Use of antibiotics, diuretics or other drugs that can influence diuresis (tricyclic antidepressants, chlorpropamide, oxcarbazepine, selective serotonin reuptake inhibitors, chlorpromazine and carbamazepine). * Use of drugs that influence intestinal motility (such as loperamide) * Anomalies of the mouth that might interfere with the intake / absorption of the medication