tranquilize

(verb) make calm or still. Synonyms: calm, calm down, quiet, tranquillize, tranquillise, quieten, lull, still. Examples: "Quiet the dragons of worry and fear."

(verb) cause to be calm or quiet as by administering a sedative to. Synonyms: sedate, calm, tranquillize, tranquillise. Examples: "The patient must be sedated before the operation."