Doxylamine
"I've taken 25 mg for five nights and found that it does help me sleep. Unfortunately, it can put me asleep for 12 hours, leaving me feeling groggy and unwilling to do much else for the rest of the day. I might use it on days when sleep is badly needed and I've nothing to do the next day. Possible side effects for elders are serious and apply to me, so that also will limit my use. "