Taking hydroxyzine and melatonin together may cause added sedation, CNS effects, and respiratory depression. This could also cause unusual sleep-related behaviors or changes in mood or behavior. Since the melatonin didn’t seem to be effective, it may be best to discontinue the melatonin. If the hydroxyzine doesn’t work, discuss with your. What is Hydroxyzine Hangover Reddit. Likes: 589. Shares: 295.