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PPDA > Opioids > Flashcards

Opioids Flashcards

1
Q

Define an opioid (1)

A

any drug that mimics endogenous opioid peptides by causing prolonged activation of opioids receptors

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2
Q

Define an opiate (1)

A

any synthetic morphine-like drug without a peptide structure

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3
Q

Endogenous opioids are derived from 3 different peptides (3)

A

B-endorphins, Encephalins, Dynorphins

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4
Q

Describe opioid receptor activation (3)

A

G-protein coupled

opens K+ channels and closes Ca++ channels

causes hyperpolarisation and inhibits NT release

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5
Q

What is the variation between Diamorphine and Morphine (1)

A

Diamorphine is more lipid soluble so has a more rapid onset of action when given IV

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6
Q

Which opioid can be given transdermally for pain? (1)

A

Fentanyl

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7
Q

Describe the specific use of Pethidine and why (2)

what are the downsides (1)

A

Used for childbirth pain

does not inhibit contractions, rapid onset + shorter duration of action

neonate may need nalaxone to treat respiratory depression

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8
Q

Describe the variations of buprenorphine from other opioids (1)

Which receptor does it act upon and how (1)

A

Has a longer duration and a slower onset and can therefore cause prolonged vomiting

partial agonist of Mu receptors

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9
Q

Can weak opioids cause tolerance? (1)

A

Yes but to a lesser extent

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10
Q

What are the effects of opioids use? (4)

A

Euphoria

sedation

analgesia

respiratory depression

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11
Q

Name the opioid receptors and state what activates them (8)

A

Mu - acted on by B-endorphins

Delta - acted on by B-endorphins and enkephalins

Kappa - acted on by dynorphins

ORL1 - non classical receptor acted on by nociceptin/OFW
has shared homology and also uses Gi/Go and has an endogenous ligand

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12
Q

What are B-endorphins made from? (1)

A

Propriomelanocortin

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13
Q

What are enkephalins made from? (1)

A

Proenkephalin

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14
Q

What are dynorphins made from? (1)

A

Prodynorphin

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15
Q

What is nociceptin made from? (1)

A

Pronociceptin

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16
Q

Where are Mu receptors located? (4)

A

Rostral and caudal cortex and motor regions eg caudate

Limbic structures eg amygdala and stria terminalis

Reward areas eg accumbens

Pain Processing areas eg Thalamus and colliculi

17
Q

Where are the Delta receptors located? (3)

A

Limbic structures eg amygdala and stria terminalis

Reward areas eg accumbens

Pain Processing areas eg Thalamus and colliculi

18
Q

Where are the Kappa receptors located? (3)

A

Limbic areas

Sensory and Motor Structures

Some expression in endocrine areas such as the hypothalamus - KEY

19
Q

Effects of opioids and their mechanisms (8)

A

Analgesia (tissue injury and tumour growth) no as effective at neuropathic pain as it effects the limbic system

Euphoria - strong contentment and decreased anxiety from pain

Resp Depression - less sensitivity to CO2 centre via Mu receptors - most damaging

Cough Reflex - reduces, unknown mechanism (low doses pre analgesia)

N&V - action in area postrema by delta and area prostrema by Mu

Pupil constriction - pinpoint pupils sign of poisoning

GI Tract - increase tone and low motility cause constipation

Itching - morphine release histamine from mast cells

20
Q

Opioid Tolerance (2)

A

develops rapidly and needs to be increased reapidly

less for GI symptoms

21
Q

Physical opioid dependence symptoms and facts (3)

A

irritable, weight loss,, shakes, writhing, jumping and aggression

less intense with gradual withdrawal

rarely progresses to addiction

22
Q

Gi/Go receptor activation (4)

A

increase K+ channel opening causing hypoerpolarisation

decrease opening of VGCC

inhibition of AC, decrease in Ca++ and PKA

opioids decrease excitation in dorsal spinal cord from peripheral neurons

23
Q

Descending control system of opioids (4)

A

opioids excite PAG neurons and neurons of nucleus reticularis paragigantocellularis (NRPG)

stimulates neurons in nucleus raphe magnus (NRM)

5-HT and enkephalin neurons of NRM run to dorsal horn and inhibit transmission

opioids act directly on dorsal horn also on peripheral terminals

24
Q

Receptor and effects of Diamorphine (2)

A

MOP

pain relief for tissue injury and tumour growth

25
Q

Receptor and effects of Pethidine (2)

A

DOP

analgesia in labour

26
Q

Receptor and effects of Fentanyl (2)

A

MOP

rapid onset and shorter action - patient controlled

27
Q

Effects of Codeine (3)

A

readily absorbed oral analgesic for mild pain

no euphoria

constipation

28
Q

Use of Dihydrocodeine and why (2)

A

useful in 10% resistant to codeine

lack demethylating enzyme that connects codeine to morphine

29
Q

Receptor effect of Tramadol (2)

A

opioid agonist

weak NA reuptake inhibitor

30
Q

Nalaxone effect and unique factor (2)

A

antagonist

does not cross BBB

31
Q

Chronic Pain and Addiction to opioids (2)

A

properly managed short term medical used rarely leads to addiction, just physical dependence

risk increases when used in ways other than prescribed (increase dose, different administration, combine with alcohol, history of psychiatric disorder, genetic polymorphisms, age (adolescents/older)

32
Q

Morphine in MOP KO mice (4)

A

demonstrated that MOP is the primary receptor for morphine - Keiffers et Al

mice have a preference to morphine in WT

in KO they no longer self administrate

MOP is a mediator of positive reinforcement

33
Q

Effect of KOP KO in mice (3)

A

WT spent 400 seconds longer in non-KOP against the injection chamber

KO mice had none of this suggesting KOP is aversive or dysphoric

KO mice had increased dopamine suggesting KOP decreases dopamine

34
Q

Mechanism of opioid dependence (4)

A

homeostatic compensatory neuradaptation - adaptive changes to oppose drug action, withdrawal causes rebound effect

HPA axis is hyporesponsive in heroin and cocaine addicts

CRF increased in amygdala

CRF antagonists block withdrawal in animals

35
Q

Treatment for dependence symptoms and mechanism (2)

A

Lafexidine

central a2 agonist that suppresses some withdrawal components

36
Q

Treatment for opioids by substitution and mechanism (4)

A

Methadone

long acting drug causes no euphoria to morphine

duration 24-36h

30-40mg stops withdrawal but leaves craving
80-100mg is more effective at lowering opioid use as it lowers craving

37
Q

Treatment for opioids that aims to prevent Euphoric feelings and mechanism (4)

A

Naltrexone

opioid agonist that prevent impulsive use by blocking agonist effects

dose is 50mg daily, 100mg every 2 or 150mg every 3

side effects involve hepatotoxicity so LFTs required every 3 months and not currently approved for opioid dependence

38
Q

Treatment for opioids by substitution and mechanism (4)

A

Burpenorphine

partial MOP/KOP agonist and KOP antagonist

lower risk of respiratory depression

used with nalaxone

PPDA (14 decks)

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