Response to desmopressin as a function of urine osmolality in the treatment of monosymptomatic nocturnal enuresis: a double-blind prospective study.

To determine if urine osmolality parameters can predict whether children with primary monosymptomatic nocturnal enuresis will respond to desmopressin, we conducted a prospective, double-blind, placebo-controlled study in 96 children 8 to 14 years old. Following a 2-week baseline screening interval patients with at least 6 of 14 net nights were randomized to double-blind regimens of desmopressin or placebo. Urine specimens for osmolality were collected at 6 p.m. and 6 a.m. on 3 consecutive days during the baseline and the 2, 14-day treatment periods. A significantly greater proportion of desmopressin treated children had an excellent (2 or fewer wet nights in 14 days) or good (greater than 50% reduction in wet nights) response compared with placebo treated children (p = 0.004 and p = 0.002 for treatment periods 1 and 2, respectively). Children treated with desmopressin reported a significantly lower number of wet nights than placebo treated children during both treatment periods (p = 0.0258 and p = 0.0136, respectively). Children treated with desmopressin had a significantly higher 6 a.m. urine osmolality during both treatment periods and a higher 6 a.m.-to-6 p.m. osmolality ratio (p = 0.004) in the first treatment period compared with the placebo group. Within the desmopressin treatment group clinical responders had a higher 6 a.m. urine osmolality and 6 a.m.-to-6 p.m. urine osmolality ratio than nonresponders during both treatment periods but these differences did not achieve statistical significance. In conclusion, treatment with desmopressin is associated with a significant decrease in the number of wet nights, and a significant increase in nocturnal urine osmolality and nocturnal/diurnal urine osmolality ratios. However, clinical response was not predictable based on baseline or treatment osmolality parameters.