Desmopressin is a man-made replacement for the hormone vasopressin. Vasopressin controls the reduction of urine during sleep and by taking desmopressin it should reduce the chances of you/your child bed-wetting. As bed wetting is caused by the inability to wake up when needing the toilet, or an inability to control the bladder, by taking this replacement hormone you should not produce as much urine during the night so these problems are averted.