OPIOID ANALGESICS

1. OPIOID ANALGESICS DR.SOBAN SADIQ

2. OPIOID AGONISTS • Morphine(strong mu receptor agonist) • Codeine • Heroin • Pholcodine • Meperidine(pethidine) • Loperamide(over the counter for diarrhea) • Diphenoxylate • Dextromethorphan

3. Opioid agonist-antagonist/partial agonist • Nalbuphine • Pentazocine • Opioid antagonists • Nalorphine • Naloxone • Naltrexone

4. Opioid receptors • Mu • Kappa • Delta

5. MOA OF MORPHINE • Certain opioid receptors are located on primary afferent and spinal cord pain transmission neurons(ascending pathways) and on neurons in the midbrain and medulla(descending pathways) that function in pain modulation. • All 3 receptors appear to be involved in anti nociceptive and analgesics mechanisms.

6. Presynaptically: • Opioid receptor activation can close voltage –gated calcium ion channels to inhibit neurotransmitter release. • ( serotonin, glutamate and substance P)

7. Postsynaptically: • Activation of these receptors can open potassium ion channels to cause membrane hyperpolarization(inhibitory post synaptic potential). • -Direct inhibition of neurons in ascending pathways.

10. Pharmacological effects CNS: • Analgesia: most powerful drug available for relief of pain • Euphoria: addict experiences a pleasant floating sensation and freedom from anxiety and distress. • Sedation • Respiratory depression: Main cause of death from opioid overdose • due to reduced responsiveness of respiratory centre in brainstem to blood levels of CO2.

11. Increase arterial CO2 retention causes cerebral vasodilation resulting in increase intracranial pressure • Cough suppression: suppression of cough centre in nucleus of tractus solitarius • Miosis: results from stimulation of Edinger- Westphal nucleus causing pin-point pupilsexcept meperidine. • Emesis: due to stimulation of brainstem chemoreceptor trigger zone results in nause and vomiting

13. CVS: No significant direct effect on CVS • Hypotension may occur if CVS is already stressed. Due to the peripheral arterial and venous dilation resulting from histamine release. • GIT: Decrease intestinal propulsive peristalsis and stomach motility leads to constipation • Biliarytract:Constriction of biliary smooth muscles leads to biliary colic except meperidine • Constriction of sphincter of oddi leads to increase biliarypressure,reflux of biliary and pancreatic secretions and elevated plasma and lipase levels

14. Renal functions: depressed due to decrease renal plasma flow. • Also has antidiuretic effect.Mechanism involve both CNS and peripheral site • Ureteral and bladder tone is increased • Increased sphincter tone….urinary retention • Occasionally, ureteral colic caused by renal calculus is made worse by opioid induced increase in ureteral tone

15. Uterus: decrease uterine tone lead to prolong labor • Skin: flushing and warming ,sweating,itching due to histamine release • Summary • Biliary, bladder,ureter tone inc. except meperidine (which block M receptors) • GIT,uterine tone dec.

16. Clinical uses • Analgesia for • MI, • terminal illness, • surgery, • obstetrical procedures, • cancer. • Cough • Diarrhea

17. Acute pulmonary edema: decrease dyspnea • Proposed mechanism : • Reduced anxiety(perception of shortness of breath) • Reduced cardiac preload(reduced venous tone) • Reduced afterload(decreased peripheral resistance) • If respiratory depression is there then use furosemide

18. Adverse effects

19. Tolerance

20. Tolerance occur due to receptor uncoupling. • Physical dependence: • It results in withdrawal(Abstinence) syndrome if there is failure to continue administer drug. Sudden withdrawal(abstinence syndrome)has following signs/symptoms: • lacrimation,yawning,chills,hyperventilation,hyperthermia,diarrhea,vomiting,anxiety

21. Psychological dependence: • euphoria, • Indifference to stimuli and • Sedation • Morphine poisoning….antidote is naloxone

22. 1-A 57 year old man presented with steady, severe pain in the right hypochondrium, nausea, vomiting and temperature of 102 F. If hepatobiliary imaging reveals an obstructed cystic duct, which of the following agents would be the drug of choice for the treatment of this patient’s pain? • a-Meperidine • b-Morphine • c-Naproxen • d-Diphenoxylate • e-Loperamide

23. Fentanyl patches(opioid) have been used to provide analgesia. The most dangerous adverse effect of this mode of administration is • a-Cutaneous reactions • b- Diarrhea • c- Hypertension • d- Relaxation of skeletal muscle • e- Respiratory depression

24. Mr. Naseem is on his way to take an examination and he suddenly gets an episode of diarrhea. He stops at a nearby drug store for an over the counter opioid with anti diarrheal action, what would be his choice: • a-Codeine • b-Dextromethorphan • c-Diphenoxylate • d-Loperamide • e-Nalbuphine

25. Which of the following opioid analgesics is a strong mu receptor agonist? • a- Naloxone • b- Morphine • c-Nalbuphine • d- Hydrocodone • e-Naltrexone

26. Morphine causes the following effects EXCEPT: • a) Constipation • b) Dilatation of the biliary duct • c) Urinary retention • d) Respiratory depression

27. The antidote of choice for morphine poisoning is • A-Naltrexone • B-Naloxone • C-Nalbuphine • D-Codeine

28. Which of the following opioid analgesic is used for relieving the acute, severe pain of renal colic: • a-Morphine • b- Naloxone • c- Codeine • d- Meperidine • e-Naltrexone

29. Opioid acts presynaptically by blocking • Sodium channels • Potassium channels • Calcium channels • Serotonin channels • GABA channels