Strong agonist

• Heroin


  Diamorphine, diacetylmorphine - potent , fast-acting
• Methadone

  • Bioavailability far exceeding than morphine
  • Used in opioid abuse
  • Tolerance develop more slowly than morphine
  • Used for chronic pain, opioid abstinence syndrome, heroin users
• Fentanyl


  Subgroups - sufentanil, alfentanil, remifentanil
• Sufentanil

  5 to 7 more potent than fentanyl
• Alfentani 


  Less potent than fentanyl
• Alfentanil


  Acts more rapidly than fentanyl
• Remifentanil  


  Half-life is extremely short
• Fentanyl 


  100 times more potent than morphine
• Sufentanil 


  1000 times more potent than morphine
• Fentanyl and sufentanil are used as anesthetic adjuvant
• Meperidine ( pethidine )

  • Antimuscarinic effect
  • Contraindication if tachycardia
  • Not as much constipation as morphine
  • Not delay the birth process
• Levorphanol 


  • Synthetic opioid
  • Serotonin - norepinephrine reuptake inhibition
  • Closely resembling morphine
  • NMDA receptor agonist
• Fentanyl 


  Synthetic opioid