Objective To measure the effect, of intranasal desmopressin (1-deamino
8-D-arginine vasopressin, DDAVP) on urine osmolality in a group of pa
tients with persistent: primary enuresis, and to determine whether cha
nges in osmolality can the predict. response to treatment. Patients an
d methods Thirty-seven patients with persistent primary nocturnal enur
esis were entered into a double-blind placebo-controlled crossover tri
al of 20 mu g intranasal DDAVP spray, Mooting urinary osmolality was m
easured on two occasions during each phase of treatment and the clinic
al response recorded in a diary. Results Thirty-one patients (22 males
and nine females) were evaluable at the end of the trial period. A go
od clinical response, defined as enuresis an two nights or fewer each
week, occurred in 12 of 31 (39%) patients, but complete continence was
attained in only two. The response was better in older patients and i
n those with less frequent enuresis. The mean and peak urinary osmolal
ity of the morning urine samples were higher while on treatment with D
DAVP compared with placebo, but this difference was not statistically
significant and the response did not predict a good clinical outcome i
n improving the enuresis. Conclusions Treatment with DDAVP can produce
a socially acceptable level of dryness in some patients with refracto
ry nocturnal enuresis. However, the early morning urinary osmolality,
as a reflection of changes in nocturnal osmolality, was not useful in
distinguishing this group or in selecting those who will respond to tr
eatment.