Diphenhydramine
"Works excellent if you haven't built a tolerance to it. After a few days of use you may find the medicine is less effective than it was when you first used it. 



Benadryl knocks me out quite quick when I use it, the only problem I have with it is that I tend to oversleep or wake up groggy the morning after, which is generally relieved with some sort of caffeinated beverage."