Combination therapy (desmopressin plus oxybutynin) improves the response rate compared with desmopressin alone in patients with monosymptomatic nocturnal enuresis and nocturnal polyuria and absence of constipation predict the response to this treatment.

• We found that 59 patients (75.6%) treated with evening administration of 240 mcg of sublingual desmopressin plus 0.3-0.5 mg/kg of oxybutynin had an improvement of response compared to treatment with desmopressin alone. • We add evidence that presence of frequently recurring nocturnal polyuria and absence of constipation are predictors of response to CT.