Other depressant drugs, anesth drugs, tranquilizers, sedatives, hypnotics, alcohol. Tranquilizer especially phenothiazine acts as antagonist to analgesic effect of opioid agonist. Dextroamphetamine may inhibit analgesics of opioid agonist. Do not administer concomitantly w/ MAOIs & w/in 14 days after the administration of MAOIs.