soporific
so-po-rif-ic
adjective
Causing or tending to cause sleep or drowsiness.
"The long, dull speech was soporific."
noun
A drug or other substance that induces sleep.
"She took a soporific to help her rest."
Thesaurus
Synonyms: hypnogogic, hypnagogic, depressant, soporiferous, somnific, somniferous, uninteresting, narcotic, hypnotic