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Stage 3 Case 1 > Opioids > Flashcards

Opioids Flashcards

1
Q

Opioids system =

A

Opioid receptors + endogenous ligands

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2
Q

MOR

A

μ-opioid receptors.

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3
Q

What are endogenous ligands?

A

They can be selective. For example, selectively bind to MOR. Some are non-selectively and can bind to any receptor.

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4
Q

Can opioid endogenous ligands bind to NOP?

A

No. It has its own ligand (nociceptin/orphanin) that can only bind to it.

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5
Q

4 levels of the nervous system that morphine acts on

A
  1. Nociceptors
  2. Spinal cord
  3. Supraspinal sties
  4. Limbic system
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6
Q

Where are opioid receptors found?

A
  • CNS: cortex, thalamus, periaqueductal grey, spinal cord
  • Peripheral neurons
  • Inflamed tissue
  • Immune cells
  • Respiratory and GI tract
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7
Q

What is the overall effect of opioids?

A

The reduction and inhibition of the neurotransmission (reduced release of substance P) that results in and analgesic effect.

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8
Q

What causes release of substance P?

A

Activation of peripheral nociceptive fibres causes release of substance P and other pain-signalling neurotransmitters from nerve terminals in the dorsal horn of the spinal cord

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9
Q

MOA opioids

A
  1. Release of pain-signalling neurotransmitters is regulated by endogenous endorphins or by exogenous opioid agonists by acting presynaptically to inhibit substance P release, causing analgesia
  2. Reduction or inhibition of neurotransmission, due to opioid-induced presynaptic inhibition.
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10
Q

MOA opioids Involves changes in transmembrane ion channels conductance…

A

– Increase potassium conductance (hyperpolarization)
– Inactivation of calcium channels
This leads to inhibition of neurotransmitter release

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11
Q

What leads to a reduction in the intracellular cyclic AMP levels?

A

Binding of an opioid agonist to a G-protein-coupled opioid receptor leads to dissociation of alpha and beta subunit form delta. This leads to inhiation of Adenylate cyclase.

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12
Q

Sedation and anxiolysis (Pharmacological effects to opioids)

A

– Drowsiness and lethargy
– Apathy
– Cognitive impairment
– Sense of tranquillity

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13
Q

Depression of respiration (Pharmacological effects to opioids)

A
  • Main cause of death from opioid overdose

- Combination of opioids and alcohol is especially dangerous

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14
Q

Cough suppression (Pharmacological effects to opioids)

A

-Opioids suppress the “cough centre” in the brain

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15
Q

Pupillary constriction (Pharmacological effects to opioids)

A

-pupillary constriction in the presence of analgesics is characteristic of opioid use

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16
Q

Nausea and vomiting (Pharmacological effects to opioids)

A
  • Stimulation of receptors in an area of the medulla called the chemoreceptor trigger zone causes nausea and vomiting
  • Unpleasant side effect, but not life threatening
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17
Q

Gastrointestinal symptoms (Pharmacological effects to opioids)

A

-Opioids relieve diarrhoea as a result of their direct actions on the intestines

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18
Q

Other effects (Pharmacological effects to opioids)

A
  • Opioids can release histamines causing itching or more severe allergic reactions including bronchoconstriction
  • Opioids can affect white blood cell function and immune function
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19
Q

Receptor type μ location

A

Brain and spinal cord

20
Q

Receptor type μ effects

A

Analgesia, respiratory depression, euphoria, addiction, ALL pain messages blocked

21
Q

Receptor type κ location

A

Brain and spinal cord

22
Q

Receptor type κ effects

A

Analgesia, sedation, all non-thermal pain messages blocked

23
Q

Receptor type δ location

A

Brain

24
Q

Receptor type δ effects

A

Analgesia, antidepressant dependence

25
Q

Why are opioids highly addictive when repeatedly used?

A

Their strong rewarding effects of enhancing dopamine levels.

26
Q

Why might opioids not be additive to some types of pain such as cancer pain?

A

As the pain relief is rewarding enough, so the drug will not be desired for other effect. The rewarding effect is not seen when pain is present.

27
Q

Pharmacological tolerance of opioids

A

Development of tolerance to analgesic effects of morphine leads to increased doses.

28
Q

At the cellular level there are two different processes of opioid induced tolerance

A

‘within process’ and ‘between process’

29
Q

‘between process’

A

drug of administration recruits different neuronal circuits that oppose the primary effect; activation of pronociceptive processes after opioid administration that counteract opioid analgesia e.g. engaging NMDA receptors

30
Q

‘within process’

A

drug of administration elicits opposing reaction within the same system; involve desensitization, internalization, down-regulation and phosphorylation of opioid receptor or heterodimerization with other receptor.

31
Q

What can happen with prolong use of morphine in terms if the NMDA receptor?

A

Tolerance. This is due to the morphine causing activation of the NMDA receptor. This triggers the activation of pain singling protein, inhibiting morphine’s analgesic activity.

32
Q

How can NMDA receptor antagonists prevent or even reverse morphine tolerance?

A

By decreasing the activation of pronociceptive processes that are triggered by opioids.

33
Q

What could be the effects of blocking NMDA receptor?

A

Could reduce hypersensitivity in chronic pain and improve the analgesic efficacy of morphine by reducing tolerance

34
Q

What does an increase in intracellular calcium cause in terms of morphine tolerance?

A

The increase in intracellular calcium and subsequent kinase activation that occurs following MOR receptor activation by morphine can remove the Mg2+ block of the NMDA receptor and this activation contributes to the development of morphine tolerance.

35
Q

Opioid-induced hyperalgesia

A

Enhanced pain response to a noxious stimulus.

Pain experienced may be the same as the underlying pain or not.

36
Q

Two possible outcomes of long-term use of opioids?

A

Hyperalgesia or tolerance. Both decreasing the effectiveness of the given dose of drug.

37
Q

Hyperalgesia can be a symptom of what?

A

Opioid withdrawal when abruptly stopped.

38
Q

How many proposed mechanisms of OIH development?

A

5

39
Q

Mechanisms of OIH 1

A

The central glutamatergic system (NMDA, CRGP, sub P)

40
Q

Mechanisms of OIH 2

A

Spinal dynorphins (with CCK),

41
Q

Mechanisms of OIH 3

A

Descending facilitation (from RVM, on and off cells),

42
Q

Mechanisms of OIH 4

A

Genetic mechanisms (genetic polymorphism; 500 genes!),

43
Q

Mechanisms of OIH 5

A

Decreased reuptake of neurotransmitters from the primary afferents.

44
Q

What is considered the most common Mechanisms of OIH?

A
  1. The central glutamatergic system (NMDA, CRGP, sub P)
45
Q

Opioids examples (3)

A

Morphine
Codeine
Oxycodone

46
Q

Opioids pain target

A

Nociceptive, inflammatory, some neuropathic, idiopathic pain relief.

47
Q

How do opioids work?

A

Activates the mu-opioid receptor system.

Stage 3 Case 1 (12 decks)

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