Desmopressin
Desmopressin is a synthetic analog of arginine vasopressin, which reduces urine output. We believe that desmopressin treats nocturnal enuresis by decreasing urine volume at night. Desmopressin has been available as an intranasal spray and in tablet formulations for the treatment of primary nocturnal enuresis for many years; a convenient, sublingual oral desmopressin lyophilisate (MELT) formulation is a more recent development [15,16]. Success rates and making the decision to switch from tablet to MELT formula were compared. Juul et al. reported that the probability of being a responder to desmopressin therapy, along with compliance, was higher in those who used the MELT formula [17]. It is a well-tolerated drug with some uncommon side effects such as headache and emotional disturbances, and a very rare possible side effect of water intoxication [13].
In the Cochrane review, it was reported that desmopressin was effective in reducing bedwetting compared with placebo but that no difference persisted after treatment was finished [18]. Recent papers also reported that desmopressin therapy has a response rate of 70% during the treatment period. Discontinuation of therapy causes a high relapse rate, which can reach 60% [3,13]. There are two factors responsible for this high relapse rate. The first one is “the definition of success”. In order to interpret the results, initial response is defined as a 50% decrease in wet nights, partial response is a 50–99% reduction in wet nights, and full response is 100% reduction [4]. In our opinion, success should be defined as “complete dryness”. The other factor is the withdrawal method for desmopressin; although it has been in widespread use for years, the best withdrawal method is still not clear. Ferrara et al. compared two withdrawal methods: abrupt withdrawal and structured withdrawal (60 μg/day for 15 days, and then 60 μg every second evening for another 15 days). They did not find a difference in relapse rate between the groups [19]. These results were not supported by the study of Haciyev and colleagues who compared relapse rates in four groups of enuretics, in which two different structured withdrawal strategies were compared to placebo and sudden withdrawal. The reported relapse rates after structured withdrawal with MELT formulation were lower. They also found that high initial dose, and a higher number of wet nights before treatment was initiated, was associated with higher relapse rates [20]. In our opinion, sudden withdrawal of the drug does not correct the disorder but just corrects the inappropriate rhythm of arginine vasopressin secretion.