- Current treatment with any drug interfering with morphine: central nervous system depressants (other narcotic analgesics, general anesthetics, phenothiazines, tricyclic antidepressants, tranquilizers, sedatives, hypnotics, antiemetics, and alcohol), muscle relaxants, mixed agonist/antagonist analgesics (i.e., pentazocine, nalbuphine, and butorphanol), cimetidine, monoamine oxidase inhibitors (MAOIs), anticholinergics.