Clinical use

• For severe , constant pain

  Not for sharp , intermittent pain
• Cancer pain and other terminal illness require continuous use
• Opioid are often used during obstetric labour but care as it can cross the placental barrier
• Meperidine produce less respiratory depression than morphine
• Main use for acute pulmonary edema 


  Frusemide ( not opioid )
• Reduce anxiety and cardiac preload and overload but respiratory depression is problem
• Morphine is particularly useful when treating painful myocardial ischemia with pulmonary edema
• Cough

  Lower dose
• All opioid agonist reduce shivering but meperidine has anti shivering property
• Diphenoxylate or loperamide is used for diarrhoea
• Most opioid have significant first pass metabolism
• Renal disease alter the pharmacokinetics of

  • Morphine
  • Codeine
  • Dihydrocodeine
  • Meperidine
  • Propoxyphene
• Routes

  • Oral
  • IV
  • IM
  • SC
  • Spinal
  • Rectal
  • Transdermal
• Avoid usage ( Diminish analgesia )

  Full agonist + Partial agonist

  Morphine + Pentazocine
• Avoid use in patients with head injury 


  CO2 retention ~ Cerebral vasodilation ~ elevated intracranial pressure
• Avoid use in impaired pulmonary function due to acute respiratory failure
• Avoid use in impaired hepatic or renal function since liver mainly metabolizes and half-life is prolonged if impaired renal function
• Avoid use in adrenal insufficiency ( Addison's disease ) and hypothyroidism ( myxedema) because of prolonged response