Increased renal concentrating ability after long-term oral desmopressin lyophilisate treatment contributes to continued success for monosymptomatic nocturnal enuresis.

OBJECTIVES: To investigate renal concentrating ability after long-term fast-melting oral desmopressin lyophilisate treatment in children with monosymptomatic nocturnal enuresis. METHODS: The present retrospective study involved 58 children (43 boys, 15 girls; aged 6-12 years) with nocturnal enuresis receiving oral desmopressin lyophilisate. After treatment for 4 weeks with a complete response, patients were placed on a reduced dose of 120 µg on alternate days. Moring urine osmolality was measured using urine samples obtained after medication and non-medication dry nights. Patients who experienced ≥1 wet nights/month during alternate-day oral desmopressin lyophilisate treatment or within 6 months after its cessation were assigned to the relapse group, whereas those who experienced <1 wet night/month were assigned to the continued success group. RESULTS: The continued success and relapse groups included 41 and 17 patients, respectively. The mean duration of treatment was 18.5 and 18.3 months in the continued success group and relapse group, respectively. There was no significant difference in morning urine osmolality after medication nights between the continued success and relapse groups; however, morning urine osmolality after non-medication nights was significantly higher in the continued success group than in the relapse group (P < 0.0001). Similarly, nocturnal urine volume was significantly higher in the relapse group than in the continued success group (P = 0.046). CONCLUSIONS: These results suggest that patients receiving long-term oral desmopressin lyophilisate treatment develop increased nocturnal renal concentrating ability, which results in sustained dryness even after treatment cessation.