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Pharm > Lecture 18: Opioids > Flashcards

Lecture 18: Opioids Flashcards

1
Q

What is Opium?

A

Dried latex obtained from the poppy

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2
Q

What are Opiates?

A

Any drug derived from opium

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3
Q

What is an Opioid?

A

Any drug that binds to an opiod receptor

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4
Q

What is Narcotic?

A

Originally used to refer to any drug with sleep inducing properties but now used by law enforcement to refer to illegal use of opioids for non-medical purposes

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5
Q

What are Synthetic Opioid Agonists?

A

Drugs or compounds that have been manufactured to bind to the same receptors that opium and opiates do but do not naturally occur within the opium poppy

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6
Q

What are examples of Synthetic Opioid Agonists?

A

Fentanyl, Heroin, Oxycontin

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7
Q

What kind of receptors are Opioid receptors?

A

The are inhibitory G-protein coupled receptors

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8
Q

What does activation of Opioid receptors do?

A

They inhibit calcium channels, activate K+ channels and inhibit adenylyl cyclase

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9
Q

What are the four types of opioid receptors?

A

Mu, Kappa, Delta, ORL1

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10
Q

Why do the different opioid receptors produce such diverse effects in the brain?

A

They are found in different parts of the brain.

Different drugs are selective to different receptors

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11
Q

Where is the ORL-1 receptor widely expressed?

A

In the the CNS

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12
Q

What is the most widely expressed opioid receptor in the brain?

A

The ORL-1 receptor

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13
Q

What are the extracellular loops of opioid receptors important for?

A

Controlling which ligands bind

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14
Q

What are the intracellular loops of opioid receptors important for?

A

The control which type of G proteins bind

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15
Q

What does activation of the mu opioid receptor cause?

A
  • Analgesia
  • Reward/euphoria
  • Respiratory depression
  • Antitussive
  • Constipation
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16
Q

Why do Mu opioid agonists cause constipation?

A

Because they inhibit gut motility

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17
Q

What is Narcotic gut?

A

When people on narcotics long term to manage pain have constipation because mu agonist inhibit gut motility

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18
Q

What drugs are Mu opioid agonists?

A
  • Morphine
  • Codeine
  • Heroin
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19
Q

What are Mu receptor antagonists used for?

A

Opioid addiction or to prevent overdose

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20
Q

What is an example of a Mu antagonist?

A

Naloxone

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21
Q

What effects do Mu antagonists have?

A
  • Aversive
  • Prevent reward
  • Block overdose
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22
Q

What is an example of a Mu antagonist?

A

Naloxone

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23
Q

What are the effects of agonists at the Delta receptors?

A
  • Not rewarding
  • No analgesia (except in chronic pain)
  • Seizure inducing
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24
Q

What are the effects of antagonists at the Delta receptors?

A

There are no obvious effects

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25
Q

What are the effects of agonists at the Kappa receptors?

A
  • Aversive
  • Hallucinogenic
  • Anxiogenic (anxiety)
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26
Q

What is an example of a Kappa receptor agonist?

A

Salvia

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27
Q

What are the effects of antagonists at the Kappa receptors?

A

Potential antidepressant/anxiolytic (reduce anxiety)

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28
Q

What are the full mu opioid receptor agonists?

A

Morphine
Methadone
Fentanyl
Heroin

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29
Q

What is the partial mu opioid receptor agonists?

A

Buprenorphine

30
Q

What are the consequences of Buprenorphine being only a partial agonist at the mu opioid receptor?

A

It has less analgesic effect and less respiratory depression

31
Q

Which one is more potent: Fentanyl or Morphine?

A

Fentanyl

32
Q

Is there a strong connection between efficacy and potency with opiates?

A

No you can have a partial agonist that is very potent and you can have a full agonist that is weekly potent

33
Q

What is an example of an opioid ligand that is not specific to one receptor?

A

Buprenorphine

34
Q

What receptors can Buprenorphine target and what does it do at the receptor?

A
  • Partial agonist at the mu opioid receptor

* Antagonist at the delta and kappa opioid receptor

35
Q

What is Buprenorphine important in managing?

A

Pain and opioid addiction

36
Q

What drug is used in Opioid agonist therapy?

A

Buprenorphine

37
Q

What are Biased Agonists?

A

Agonists that bind to the receptor and stimulate unique intracellular signalling pathways

38
Q

What are Beta-arrestins?

A

A family of intracellular proteins important for regulating signal transduction at GPCRs

39
Q

What is binding of Beta-arrestin intracellularly thought to do?

A

Shut off the intracellular signalling pathway. It blocks further G-protein signaling, redirects signaling to alternative pathways (beyond Gi, Gs, and Gq) and targets receptors for internalization

40
Q

What signals Beta-arrestin to bind to a receptor?

A

Phosphorylation of a GPCR after the G-protein is cleaved

40
Q

What signals Beta-arrestin to bind to a receptor?

A

Phosphorylation of a GPCR after the G-protein is cleaved

41
Q

How does Beta-arrestin work in chronic opioid use?

A

IT arrests G-protein signalling which leads to higher tolerance of the drug

42
Q

How does Beta arrestin contribute to some drug effects?

A

By activativating its own intracellular signaling

43
Q

With opioids what does the GPCR elicit?

A

Analgesia

44
Q

With opioids what does the beta-arrestin pathway elicit?

A

Depression and constipation

45
Q

What signalling pathways can Biased Agonists activate?

A

Some are better at activating the GPCR pathway and some are better at activating the beta arrestin pathway

46
Q

What is Functional Selectivity?

A

When different drugs activate the different signalling pathways depending on how it stimulates the receptor

47
Q

Why are biased agonists so important?

A

Because the different signalling pathways they target can drive different aspects of the drug

48
Q

How would a biased morphine mu agonist be beneficial?

A

It would only activate the G protein signal which leads to analgesia and not the Beta arrestin pathway that leads to respiratory depression and constipation

49
Q

What happens when Morphine is taken orally?

A

IT undergoes extensive first pass metabolism

50
Q

How is Codeine affected by first pass metabolism?

A

Codeine effect is not reduced by first pass metabolism so it is more effective orally

51
Q

Where are the highest concentrations of opioid agonists usually?

A

In highly perfused tissues such as the brain, lungs, liver, kidneys and spleen

52
Q

What is Morphine metabolized by and into what?

A

Phase II glucuronidation into morphine-3-glucuronide and morphine-6-glucuronide

53
Q

What enzyme metabolizes morphine?

A

UGT2B7

54
Q

What kind of metabolite is morphine-6-glucuronide?

A

An active metabolite

55
Q

What is Glucuronidation?

A

The addition of large polar bodies that make them more likely to be excreted

56
Q

What is codeine metabolized into?

A

Morphine

57
Q

What kind of drug is Codeine?

A

A prodrug

58
Q

What is codeine metabolized into morphine by?

A

CYP2D6

59
Q

What do genetic polymorphisms of CYP2D6 do?

A

Cause variation in analgesic and adverse responses among patients particularly for codeine

60
Q

How are poor metabolizers affected?

A

They need much higher doses of Codeine to feel an effect

61
Q

How are fast metabolizers affected by codeine?

A

They have heightened responses to codeine and find it more analgesic and need lower doses

62
Q

Where are polar metabolites mainly excreted?

A

In the urine

63
Q

How are patients with renal impairment affected by active polar metabolites (M6G)?

A

The effects of the active polar metabolite are amplified because the individual cannot excrete the actual metabolites quickly

64
Q

What are the three types of endogenous opioid peptides?

A
  • Beta endorphins
  • Enkephalins
  • Dynorphins
65
Q

What do the Endogenous peptides mediate?

A
  • Pain
  • Reward
  • Learning
  • Memory
  • Cognition
66
Q

What are endogenous opioid peptides generated from?

A

Protein precursors that are cleaved by proteases
•Proenkephalin
•Proopiomelanocortin
•Prodynorphin

67
Q

What do all endogenous opioid peptides share?

A

The common amino acid sequence Tyr - Gly - Gly - Phe

68
Q

Which receptor do beta endorphins have the highest affinity for?

A

Mu but also delta

69
Q

Which receptor is enkephalin selective for?

A

Delta>Mu>Kappa

70
Q

What is the Dynorphin peptide more selective for?

A

Kappa>mu=delta

Pharm (31 decks)

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