The effect felt the morning after taking Benedryl or other OTC drug containing diphenhydramine such as Unisom or Tylenol PM in order to induce or aid sleep. Symptoms include inability to wake up, sleeping through alarm clocks, grogginess, stiff neck, loss of memory, and general irritability. There is no known cure.
"I was late to work, I couldn't drive until I worked off this benedryl hangover"
"Dude, after all that Unisom you downed last night, I'm surprised you are still alive!"