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OPIOID ANALGESICS. DR.SOBAN SADIQ. OPIOID AGONISTS. Morphine(strong mu receptor agonist) Codeine Heroin Pholcodine Meperidine(pethidine) Loperamide(over the counter for diarrhea) Diphenoxylate Dextromethorphan. Opioid agonist-antagonist/partial agonist. Nalbuphine Pentazocine - PowerPoint PPT Presentation
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OPIOID AGONISTS
Morphine(strong mu receptor agonist)CodeineHeroinPholcodineMeperidine(pethidine)Loperamide(over the counter for diarrhea)DiphenoxylateDextromethorphan
Opioid agonist-antagonist/partial agonistNalbuphinePentazocine
Opioid antagonistsNalorphineNaloxoneNaltrexone
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.
Presynaptically: Opioid receptor activation can close voltage –
gated calcium ion channels to inhibit neurotransmitter release.
( serotonin, glutamate and substance P)
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.
Pharmacological effectsCNS: Analgesia: most powerful drug available for relief of
painEuphoria: addict experiences a pleasant floating
sensation and freedom from anxiety and distress.SedationRespiratory depression: Main cause of death
from opioid overdosedue to reduced responsiveness of respiratory centre in
brainstem to blood levels of CO2.
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 pupils except meperidine.
Emesis: due to stimulation of brainstem chemoreceptor trigger zone results in nause and vomiting
CVS: No significant direct effect on CVSHypotension 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
Biliary tract:Constriction of biliary smooth muscles leads to biliary colic except meperidine
Constriction of sphincter of oddi leads to increase biliary pressure,reflux of biliary and pancreatic secretions and elevated plasma and lipase levels
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 increasedIncreased sphincter tone….urinary retentionOccasionally, ureteral colic caused by renal calculus
is made worse by opioid induced increase in ureteral tone
Uterus: decrease uterine tone lead to prolong laborSkin: 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.
Clinical usesAnalgesia for MI, terminal illness, surgery, obstetrical procedures, cancer.
CoughDiarrhea
Acute pulmonary edema: decrease dyspneaProposed 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
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
Psychological dependence: euphoria,Indifference to stimuli and Sedation
Morphine poisoning….antidote is naloxone
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
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
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
Which of the following opioid analgesics is a strong mu receptor agonist?
a- Naloxone b- Morphine c-Nalbuphine d- Hydrocodone e-Naltrexone
Morphine causes the following effects EXCEPT:
a) Constipationb) Dilatation of the biliary ductc) Urinary retentiond) Respiratory depression
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