1 opioid analgesics & antagonists. 2 3 mainly obtained from opium poppy. act by binding to...
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OPIOID ANALGESICS
&
ANTAGONISTS
2
3
MAINLY OBTAINED FROM OPIUM POPPY.ACT BY BINDING TO SPECIFIC OPIOID
RECEPTORS IN THE CNS.MAINLY USED FOR RELIEVING INTENSE
PAIN.EUPHORIC PROPERTIESANTAGONISTS IMPORTANT IN OVERDOSE.
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OPIOID RECEPTORS5
4 TYPES Mu ( µ )Kappa ( к )Delta ( δ )Sigma ( σ )
Mu ( µ )6
Location : supraspinal areas of pain modulation (periaqueductal gray, medial thalamic nuclei, hypothalamus, limbic system)
Response : Supraspinal analgesia, euphoria, respiratory depression, sedation, physical dependence, pupil constriction, decreased GI motility.
Abuse potential : High
Kappa ( к )
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Location: Dorsal horn of spinal gray matter (substantia gelatinosa ); deep layers of cerebral cortex.
Response: Spinal analgesia, sedation, depressed flexor reflexes, pupillary constriction.
Abuse potential: Low
Delta ( δ )
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Location : Substantia nigra, globus pallidus, corpus striatum, other limbic structures.
Response: Euphoria, sedationAbuse potential : Low
Sigma ( σ )9
Location : Hippocampus.Response : Dysphoria, Hallucinations,
cardiovascular stimulation, pupil dilatation.Abuse potential : Low
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Other than these responses, Some of them are involved in depression of
cough , ↑ nausea, ↑ vomiting, neuroendocrine actions, maintainance of B.P, control of stomach secretions, and also anti-inflammatory effects.
Strong Agonists11
MorphineFentanylHeroinMeperidineMethadoneSufentanil
Moderate Agonists12
Codeine
Propoxyphene
Mixed agonist - antagonist13
Buprenorphine
Pentazocine
Antagonists14
Naloxone
Naltrexone
MORPHINE15
Main agonist actions on Mu, and also for Kappa and Sigma receptors
ACTIONS:- Analgesia – relief of pain without loss of
consciousness.- Euphoria- Causes Respiration Depression (This is the
most common cause of death in acute opioid overdose)
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- Depression of cough reflex- MIOSIS – PINPOINT PUPIL.- Stimulation of the edinger westphal nucleus
of oculomotor nerve which causes parasympathetic stimulation of the eye.
- Emesis.—stimulates chemoreceptor trigger zone (CTZ) in area postrema
- - GIT : ↓ motility, relieves diarrhea and dysentery
- CVS : high doses cause hypotension and bradycardia
17- Cerebral vessels dilate - ↑ CSF pressure
( CI – severe brain injury)- Histamine release causes
bronchoconstriction, urticaria, sweating and vasodilation.
- Hormonal actions – ( increase in prolactin, GH and ADH)
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Morphine is used legally:As an analgesic in hospital settings to
relieve Pain in Myocardial Infarction Pain after surgery Pain associated with trauma
In the relief of severe chronic pain, e.g. Cancer pain Pain from kidney stones Severe Back pain
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As an adjunct to general anesthesia In epidural anesthesia or intrathecal
analgesia For palliative care (i.e. to alleviate pain
without curing the underlying reason for it, usually because the latter is found impossible)
As an antitussive for severe cough In nebulised form, for treatment of dyspnea,
although the evidence for efficacy is slim. Evidence is better for other routes .
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As an anti-diarrheal in chronic conditions (e.g., for diarrhea associated with AIDS), although loperamide (a non-absorbed opioid acting only on the gut) is the most commonly used opioid for diarrhea.
contraindications21
acute respiratory depression acute pancreatitis (this may be a result of
morphine use as well) because morphine may cause spasm of the sphincter of Oddi and worsen the pain
renal failure (due to accumulation of the metabolite morphine-6-glucuronide)
chemical toxicity (potentially lethal in low tolerance subjects)
raised intracranial pressure, including head injury (exacerbation due pCO2 increases from respiratory depression)
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SE23
SedationConstipationNauseaVomitingUrinary retentionPotential for addictionResp. depression
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Drug interactions:MAO Inhibitors (monoamine oxidase
inhibitors )TCA’s(tricyclic antidepressant)Antipsychotic
MEPERIDINE (Pethidine )25
MECH : Binds to Kappa receptors.Actions :AnalgesiaResp. depressionIV route can cause increase in H.R.Dilates pupilDecreases GI motility ↑ CSF pressure
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USES:Any kind of analgesia – preferred for labor
analgesiaNot used for diarrhea or coughCan replace morphine or heroin in addicts.Route : oral and parental Met : liverExe : Urine
SE27
TremorsMuscle twitchesConvulsionsDilates pupilNot given with other neuroleptics and MAO
inhibitors.Cause hypotension – postoperative.
METHADONE28
MECH: More on Mu receptorsEqual potency to Morphine, but less
euphoric and longer duration of action.Actions:Mostly same as morphine.Route : oralMet: LiverExe: Urine
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USES :AnalgesiaAddicts of heroin and morphine – for
withdrawal .
SE:Less severe than morphine.
FENTANYL30
AROUND 100 TIMES MORE POWERFUL ANALGESIC THAN MORPHINE, SO USED during ANESTHESIA
Rapid action and short duration of action.Main action is on Mu, and also on kappa
sigma receptors.
HEROIN31
2-3 times more potent than morphine.More euphoriaNo therapeutic usesAddiction
PROPOXYPHENE32
Derivative of MethadoneAnalgesic for mild to moderate painSometimes used in combination with aspirin
or acetaminophen - ↑ analgesiaAlso has antitussive action (used for cough)
SE33
Nausea, ConstipationHigh doses can causeResp depression, ConvulsionConfusion, HallucinationsCardiotoxicity, Pul. edema These effects can be antagonized by
Naloxone.
CODEINE34
Good antitussive,Less analgesic than morphineCauses euphoriaSedationAddictionSo, many of the newer cough medications
do not contain codeineIt has been replaced by dextrometharphan
PENTAZOCINE35
AGONIST ON Kappa AND Partial ANTAGONIST ON Mu & delta.
Moderate painOral or parentalLess euphoric than morphineNot used with morphine.
SE36
At high dosesIncrease B.PHallucinationsNight maresTachycardiaDizzinessResp depression
BUPRENORPHINE37
AGONIST Mu receptorsParenteralModerate painMorphine withdrawalSE:Resp depressionNausea, dizziness
NALOXONE38
OPIOID ANTAGONISTRapidly reverse the effects of opioids,
which can increase withdrawal symptoms
Reverse the coma and resp depression of opioid overdose.
IV route – In 30 sec shows significant changes in resp depression and coma.
Precipitates the withdrawal symptoms in morphine and heroin abusers.
NALTREXONE39
SAME AS NALOXONELonger duration of action than naloxoneOral routeUsed in opiate dependence maintainance
programs.