Oxybutynin, desmopressin and enuresis

A review of the scarce literature concerning oxybutynin treatment for nocturnal enuresis reveals that its success is greatest when enuresis is combined with daytime incontinence. The renal and bladder related characteristics of children with monosymptomatic enuresis responsive to oxybutynin were evaluated.

Renal concentrating capacity and functional bladder capacity were compared between 55 dry children who served as controls, and children with monosymptomatic enuresis who responded to desmopressin only (group 1, 27), oxybutynin only (group 2, 11), combination desmopressin and oxybutynin (group 3, 7) or were resistant to all treatment alternatives (group 4, 23).

Renal concentrating capacity was lowest in groups 1 and 3 (939 +/- 147 mOsm./kg. controls, 856 +/- 158 group 1, 1,073 +/- 71 group 2, 762 +/- 119 group 3 and 970 +/- 146 group 4; p <0.01), whereas they had high urinary output (15.4 +/- 73.4 ml./kg. per hour controls, 22.2 +/- 10.2 group 1, 13.5 +/- 4.3 group 2, 21.5 +/- 11.2 group 3 and 15.0 +/- 6.9 group 4; p <0.01). Forced functional bladder capacity of that expected for age was lowest in groups 2 to 4 (107 +/- 43% controls, 88 +/- 43 group 1, 71 +/- 25 group 2, 68 +/- 22 group 3 and 59 +/- 22 group 4; p <0.01).

Children responding to oxybutynin have small bladders and probably hyperactive detrusors, whereas those responding to desmopressin or who need both drugs to achieve dryness have polyuria.