Abstract: Forty seven randomised controlled trials involving 3448 children (of whom 2210 received desmopressin) met the inclusion criteria. The quality of many of the trials was poor. Desmopressin was effective in reducing bed-wetting during treatment, compared with placebo (e.g. 20 µg: 1.34 fewer wet nights per week; 95% confidence interval (CI) 1.11 to 1.57), and children were more likely to become dry (e.g. 118/146, 81% versus 140/142, 98% still wet; relative risk (RR) for failure to achieve 14 dry nights with 20 µg was 0.84; 95% CI 0.79 to 0.91). However, there was no difference between the two patient groups after treatment was finished. There was no clear dose-related effect of desmopressin, but the evidence was limited. Data which compared oral and nasal administration were too few to be conclusive. In four small trials, there were no significant differences between desmopressin and alarms during treatment when these were used separately, but the chance of failure or relapse after treatment stopped was lower after an alarm in two small trials (40/62, 65% versus 26/57, 46%; RR 1.42, 95% CI 1.05 to 1.91). Although children had fewer wet nights during treatment when they used desmopressin combined with alarm treatment compared with alarms alone (WMD -0.83, 95% CI -1.11 to -0.55), there were no significant differences either in failure rates during treatment (RR 0.88; 95% CI 0.73 to 1.05) or for relapse after treatment stopped (105/213, 49% versus 118/214, 55%: RR 0.91, 95% CI 0.76 to 1.08). Comparison with some tricyclic drugs (e.g. amitriptyline) suggested that they might be as effective as desmopressin, although in two trials children were less likely to achieve 14 dry nights with imipramine than desmopressin (RR 0.44, 95% CI 0.27 to 0.73) but there was not enough information about subsequent relapse. There were more side effects with the tricyclics. Desmopressin may be better than diclofenac or indomethacin. There was not enough information to evaluate the relative effects of behavioural or complementary treatments against desmopressin. Desmopressin rapidly reduced the number of wet nights per week experienced by children, but the limited evidence available suggested that this was not sustained after treatment stopped. Comparison with alternative treatments suggested that desmopressin and tricyclics had similar clinical effects during treatment, but that alarms may produce more sustained benefits. However, based on the available limited evidence, these conclusions are only tentative. Children should be advised not to drink more than 240 ml (8 ounces) of fluid during the evening before desmopressin treatment in order to avoid the possible risk of water intoxication.

Plain-language summary: When desmopressin is used, most of the children have fewer wet nights (one night less on average per week) and more become dry (19% compared with only 2% using dummy treatment in five trials involving 288 children). However, many children start wetting again when treatment stops. On the other hand, more children remain dry when alarm treatment is finished (54% after alarm compared with 35% after desmopressin in two trials involving 119 children). Adding desmopressin to alarm treatment did not result in better cure rates after the end of treatment (51% remained dry after combination treatment compared with 45% after alarm alone). Those using desmopressin (or their parents) should be warned that over-drinking before bedtime should be avoided as this may lead to serious, but rare, adverse effects. Drugs called tricyclic antidepressants have a similar effect to desmopressin and are cheaper, but have more adverse effects. There are few adverse effects with alarms, other than short-term disruption for the family. In summary, alarms take longer to reduce bed-wetting, but their effect may persist longer than desmopressin.