Agonist/Antagonist Opioid Analgesics. When a individual has previously obtained or is at present 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.Hydromorphone injection is used to relieve pain