How can I help my 4 year old son to stop wetting the bed at night?

Treatments include: Motivational therapy-involving parents encouraging and reinforcing a child's sense of control over bed-wetting. Moisture alarms-detect wetness in the child's underpants during sleep and sound an alarm to wake the child.Desmopressin and tricyclic antidepressants- meds to increase the amount of urine that the bladder can hold or decrease the amount of urine released by the kidneys.