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Pharmacology 3001 > Pain I: Opioids - McDougall 1 > Flashcards

Pain I: Opioids - McDougall 1 Flashcards

1
Q

What is pain?

A

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

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2
Q

Nociception

A

Physiological processes in response to noxious stimuli

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3
Q

Allodynia

A

Pain in response to a normally innocuous stimuli

Enhanced pain repsonse

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4
Q

Hyperalgesia

A

Enhanced pain to a normally painful stimuli

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5
Q

Nociceptive pain

A

Direct activation of nociceptors by noxious stimuli

Ie. Touching something hot

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6
Q

Inflammatory pain

A

Activation by inflammatory mediators

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7
Q

Neuropathic pain

A

Pain arising from nerve damage

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8
Q

Pain pathway

A

Ascending processes
Nociceptor - Primary afferent - Dorsal root ganglion (cell body) - Second order neuron in SC - Brain

Pain sensation, cognitive interpretation, affective behaviour

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9
Q

Normal movement pathway

A

Ascending processes

Mechanosensors - Primary afferent - Dorsal root ganglion (cell body) - Second order neuron in SC - Brain

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10
Q

Peripheral sensitization pathway

A

Ascending processes

Nociceptor - Primary afferent - Dorsal root ganglion (cell body) - Second order neuron in SC - Brain

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11
Q

Central sensitization pathway

A

Ascending processes

Nociceptor - Primary afferent - Dorsal root ganglion (cell body) - Second order neuron - brain

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12
Q

Referred pain

A

Pain at a point in the body
Nerves in areas surrounding synapse onto the same projection neutron, giving feeling of pain in those areas too
Because of development of fetus and different derm layers

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13
Q

Glyco-heroin

A

To be used as cough suppressant

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14
Q

Mrs. Winslows Soothing Syrup

A

Opium and alcohol for soothing teething children

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15
Q

Opium

A

c. 3400 BC, lower Mesopotamia

1806: isolated morphine

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16
Q

Morphine

A

10% of opium

High analgesia, addictive

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17
Q

Codeine

A

0.3-2% opium

Less powerful analgesia, less addictive

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18
Q

Heroin

A

Bayer and Co synthetically modified morphine to reduce negative side-effects
Replaced 2H with 2CH3CO to make diacetylmorphine
Made heroin: highly potent analgesic but extremely addictive
Passes BBB better than morphine

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19
Q

Opiate

A

Drugs derived from opium

20
Q

Opioid

A

Agents with opiate-like actions
Synthetic
Proteins that mimic opiate actions
Endorphins

21
Q

Narcotic

A 
Sleep inducing (pharmacological)
Producing dependence (legal)
22
Q

Opioid receptor subtypes

A

mu, delta, kappa, NOP

23
Q

Mu opioid receptor

A

Endogenous ligand: endomorphin
Exogenous ligand: morphine, codeine, heroin
Antagonist: CTOP, DAMGO

24
Q

Delta opioid receptor

A

Endogenous ligand: enkephalin
Exogenous ligand: diprenorphine
Antagonist: Naltrindole

25
Q

Kappa opioid receptor

A

Endogenous ligand: dynorphin
Exogenous ligand: etorphine
Antaongist: nor-BNI

26
Q

NOP opioid receptor

A

Endogenous ligand: nociception
Exogenous ligand: orphanin FQ(1-11)
Antagonist: nocistatin

27
Q

Naloxone

A

Not-specific antagonist for opioid receptors

28
Q

Site of action of opioids: Periphery

A

Receptors in periphery
Reduction in production of pain causing chemicals
Reduction in release of algogenic agents
Desensitize peripheral nerve

29
Q

Site of action of opioids: SC

A

Mu opioid receptors on presynaptic terminal
Binding causes reduction of release of excitatory NT, resulting in reduction of CIP, Glu and SP, and reducing Ca influx
Postsynaptically, increasing K to cause hyperpolarization

30
Q

Site of action of opioids: Supraspinal

A

Periaqueductal grey, insular cortex, dorsal raphe nucleus, nucleus raphe magnus
Opioids bind to receptors activating descending inhibitory pathways
Spinal release of 5-HT and NA
Inhibitory nerves activated
Receptors close to respiratory centres can cause respiratory depression

31
Q

Site of action of opioids: Mesolimbic system

A

Ventral tegmental area, nucleus accumbens, amygdala
Stimulate dopaminergic circuits involved in reward, euphoria
Alters emotional response to pain

32
Q

Acute inflammation

A

Upregulation of mu-opioid receptors in DRG
Increase axonal transportation of MOR
Increase in MOR in periphery and dorsal horn
Increase opioid analgesia

33
Q

Chronic pain

A

Most painful conditions, >3mo
Opioids have reduced efficacy in chronic pain
Down regulations in areas of chronic inflammation
Opioid analgesia less effective

34
Q

Negative side effects of opioids

A

Severe constipation, somnolescence, cardiorespiratory depression
Tolerance

35
Q

Tolerance

A

Increasing doses required to achieve therapeutic level
Minimized by “start low, go slow”
Occurs 2-3 weeks after frequent opioid use

36
Q

Mechanism of tolerance

A

Desensitization and trafficking via GPCR kinases
After arrestin binding, receptor is desensitized at surface, and then internalized
Receptors either recycled to cell surface of degraded in lysosome

37
Q

Treatment of tolerance

A

Rotation to another opioid

Recouple to a non-opioid adjunct

38
Q

Dependence

A

Addiction
State of physical and psychological dependence
Preoccupation with acquiring and using drugs despite knowledge of adverse health effects
Risk factors: serious history of substance abuse, mental illness, addictive personality

39
Q

Physical dependence

A

Drug withdrawal produced physical abstinence syndrome
Mild: lacrimation, sweating, yawning
Severe: anorexia, cramps, nausea, vomiting, restlessness, irritability, tremor, HR/BP changes, chills, spasms, PAIN

40
Q

Psychological dependence

A

Compulsive drug seeking behaviour
Occurs with drugs with mood enhancing properties
Activated dopaminergic circuits (endogenous reward system)

41
Q

Treatment of dependence

A

Cessation of drug intake
Naltrexone (mu-antagonist)
Methalone (mu-agonist)

42
Q

Methalone

A

Mu-agonist
Good oral bioavailability, selective
Long-lasting and slow withdrawal

43
Q

Paradoxical opioid-induced hyperalgesia

A

Prolonged opioid use increases pain
Sensitization of peripheral nociceptors
Sensitization of dorsal horn neurons
Altered descending control mechanisms: Glu receptor involvement therefore, co-adminsiter Glu antagonist

44
Q

Polypharmacy

A

Opioid + cannabinoid: synergistic effect (mu-opioid receptors dimerize with CB1)
Opioid + low dose amphetamine: offset sedation
Opioid + antidepressant: useful for neuropathic pain

45
Q

Peripherally restricted opioids

A

Can target pain at the source
Reduce sensitization of nociceptors
Do not pass BBB
Less likely to cause addiction issues, centrally-mediated site effects like respiratory depression

46
Q

Improve opioid receptor levels

A

Inhibit beta-arrestin activity to reduce receptor internalization
Inhibit receptor degradation (proteinase inhibitors)
Promote receptor recycling

Pharmacology 3001 (19 decks)

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