You searched for: “hypnagogues
hypnagogue (s) (noun), hypnagogues (pl)
A hypnotic agent that induces sleep: Jack had problems with getting to sleep and sleeping through the night, so his doctor gave him a prescription for hypnagogue which should give him a good night's sleep!

A hypnagogue can be any agent causing sleepiness or drowsiness, like an uninteresting book or a boring movie!