Agonist/Antagonist Opioid Analgesics. When a patient has previously been given or is now undergoing a class of therapy with a pure opioid agonist analgesic like Dilaudid, agonist/antagonist analgesics like pentazocine, nalbuphine, butorphanol, and buprenorphine, ought to be used with caution.Dilaudid (hydromorphone) is a powerful opioid pain medi