上游充通大 Drug classification SHANGHAI JIAO TONG UNIVERSITY Opioid Drugs Opioid vs.Opiate u-Agonists Mixed Actions Antagonists Morphine Pentazocine Naloxone Heroin Nalbuphine Naltrexone Methadone Strong Butorphanol Meperidine Agonists Hydromorphone Fentanyl Codeine Oxycodone Weak to Diphenoxylate Moderate Loperamide AgonistsDrug classification