Reduced anti-diuretic response to desmopressin during wet nights in patients with monosymptomatic nocturnal enuresis.

Objective: To investigate why not all children with monosymptomatic nocturnal enuresis (MNE) treated with desmopressin give an adequate response.

Methods: We included 114 children with MNE aged 5-15 years (9.8 ± 0.2 years) who experienced at least 1 wet night and more than 2 dry nights during desmopressin treatment. The patients made home recordings for 2 weeks as baseline and for 2-4 weeks of desmopressin titration. Nocturnal urine production during wet and dry nights, and maximum voided volumes (MVVs) were documented in all patients.

Results: Sixty-four patients were desmopressin non-responders, 29 were either partial responders or responders, while 21 patients were full responders. Desmopressin reduced nocturnal urine production dramatically during dry nights compared with pre-treatment wet nights. Nocturnal urine production during desmopressin treatment was significantly greater during wet nights compared to dry nights (243 ± 9.32 vs 176 ± 5.31 ml, P < 0.001). There was a highly significant correlation between individual nocturnal urine output and MVV, and dry nights were characterized by nocturnal urine output/MVV ratios well below 1.0.

Conclusions: The anti-enuretic response to desmopressin seems to be dependent upon the degree of reduction in nocturnal urine production. Research on desmopressin bioavailability in children is needed.