ataractic

nouns

a drug used to reduce stress or tension without reducing mental clarity
antianxiety agent, ataractic, ataractic agent, ataractic drug, tranquilizer, tranquilliser, tranquillizer

adjectives

tending to soothe or tranquilize
"valium has a tranquilizing effect"; "took a hot drink with sedative properties before going to bed"
ataractic, ataraxic, sedative, tranquilising, tranquilizing, tranquillising, tranquillizing
is derived from
ataraxia