We evaluated combination treatment with desmopressin and oxybutynin in patients with enuresis who did not respond to desmopressin monotherapy. Furthermore, we compared 2 methods of estimating bladder capacity and evaluated the ability of these methods to predict the response to desmopressin and oxybutynin.Materials and Methods
A total of 60 children with a mean age ± SD of 10.6 ± 3.0 years who had monosymptomatic nocturnal enuresis completed the study. After a 2-week observation period maximal voided volume during free access to fluid intake was determined by a 2-day frequency-volume chart and maximal voided volume after water load was determined on a separate day. Patients then received 20 μg desmopressin intranasally at bedtime during 2 weeks. In nonresponders to desmopressin with less than a 50% decrease in wet nights 5 mg oxybutynin twice daily was added for another 2 weeks.Results
Of the patients 41 (68%) showed more than 50% decrease in wet nights during the 2-week desmopressin treatment period (4.6 ± 1.6 to 0.7 ± 0.8, p <0.001). In desmopressin nonresponders combined treatment with desmopressin and oxybutynin resulted in a further decrease in wet nights (4.0 ± 1.2 to 1.7 ± 1.4, p <0.001). Maximal voided volume during free access to fluid intake was significantly higher in desmopressin responders than in nonresponders (244 ± 111 vs 160 ± 65 ml, p <0.001). In contrast, maximal voided volume after water load was not significantly different between desmopressin responders and nonresponders.Conclusions
The study indicates a role for oxybutynin in combination with desmopressin in children who are not responding to desmopressin monotherapy. Maximal voided volume during free access to fluid intake is a clinically useful predictor of the response to desmopressin but not to oxybutynin.