narcotic
nar-cot-ic
noun
A drug that relieves pain and induces drowsiness or stupor, often addictive.
"The patient was given a strong narcotic."
adjective
Causing drowsiness, stupor, or insensibility, or relating to such drugs.
"The drug had a strong narcotic effect."
Thesaurus
Synonyms: narcotizing, narcotising, depressant, soporific, soporiferous, uninteresting