Pain Management Flashcards

0
Q

COX enzyme differences

A

COX 1 has tighter active site shape

COX 2 could be specifically targeted by using larger drugs

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1
Q

COX enzyme function

A

Convert arachidonic acid to prostaglandins G and H
COX 1 is generally cytoprotective
COX 2 is induced by injurious stimuli, may be constitutively expressed in brain and kidney

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2
Q

Prostaglandin role in pain

A

Mainly PGE
EP1 receptor - increased bradykinin sensitivity, K+ channel inhibition, increased Na+ channel sensitivity
EP2 receptor - decreased glycine receptor affinity
EP3 - pyrexia

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3
Q

NSAIDs therapeutic effects

A

Via COX 2 inhibition
Prevents arachidonic acid conversion to PGs
Analgesia
Anti inflammatory

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4
Q

NSAID pharmacokinetics

A

Oral or topically if soft tissue injury
Heavily protein bound (90-99%)
Linear pharmacokinetics within therapeutic dose range
T 1/2 - two groups - more than 10 hours (naproxen) or less than 6 (ibuprofen)

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5
Q

NSAID DDIs

A

If two NSAIDs unknowingly given together

Protein displacement-sulfonylureas, warfarin, methotrexate

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6
Q

NSAIDs ADRs

A

Hypersensitivity - aspirin induced asthma, skin rashes. Don’t give in asthma because leukotrienes
Reye’s syndrome - rare, serious - brain/liver injury
Stevens-Johnson syndrome - rash of skin and mucous membranes
Increased clotting time
Renal (reduced blood flow - PGE2 and I2 maintain renal blood flow)
GI - peptic ulcers

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7
Q

Ibuprofen

A

NSAID

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8
Q

Aspirin

A

NSAID
Irreversible COX inhibition (acetylation)
Antiplatelet
Anti GI and breast cancer?

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9
Q

Rofecoxib

Celecoxib

A

COX 2 inhibitors

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10
Q

COX 2 inhibitors

A

Should have fewer ADRs

Short term use only

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11
Q

Paracetamol mechanism

A

Unknown - weak COX inhibitor

Perhaps on COX 3 isoform in CNS

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12
Q

Paracetamol pharmacokinetics

A

First order in healthy patient
T1/2 2-4 hrs
Caution if poor hepatic function

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13
Q

Paracetamol toxicology

A
NAPQI made - depletes glutathione - hepatocyte death
Also renal failure
Give N acetyl cysteine in first 36 hrs
Methionine if can't be given promptly
Activated charcoal in first 4 hrs
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14
Q

Endogenous opioids

A

Endomorphins 1 and 2 (mu receptor)
Enkephalins - metenkephalin, leuenkephalin
Endorphins (from POMC)
Newly discovered - nociceptin, nocistatin

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15
Q

Opioid receptors

A

Mu (MOP) in CNS (supra spinal) - analgesic via increased K+ efflux
Delta (DOP) widely distributed in CNS. Bind enkephalins, work via decreased cAMP synthesis
Kappa (KOP) in spinal cord - analgesia via calcium channel block

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16
Q

Morphine

A

Opioid receptor agonist

Gold standard opioid analgesic

17
Q

Morphine structure

A

Has two hydroxyl groups - not lipid soluble

Active site is amine group

18
Q

Morphine metabolism

A

Glucuronidated to morphine 6 glucuronide or morphine 3 glucuronide
Can be screened for in urine

19
Q

Morphine oral bioavailability

A

25%

20
Q

Morphine uses

A

Terminal illness analgesia

Diarrhoea

21
Q

Diamorphine

A

Heroin

Diacetylmorphine

22
Q

Diamorphine structure

A

OH groups replaced by acetyl groups
Lipid soluble
Can cross BBB

23
Q

Diamorphine half life

A

Short as ester bonds easily broken down by pseudocholinesterases
Broken down to morphine

24
Q

Diamorphine uses

A

Analgesia terminal illness

Epidural analgesia NOT LICENSED.

25
Q

Methodone

A

Opioid used for maintenance in dependance.

26
Q

Tramadol

A

Analgesic

Has 5-HT and NA effects

27
Q

Tapentadol

A

Specific mu agonist
NA reuptake inhibitor
Analgesic

28
Q

Codeine

A

Oral
Mild analgesic
Metabolised to morphine by CYP2D6
Does not work in people with altered enzyme

29
Q

Synthetic opioids

A

Very potent

Anaesthetics

30
Q

Fentanyl

A

Synthetic opioid

31
Q

Alfenatil

A

Synthetic opioid

32
Q

Remifenatil

A

Synthetic opioid

33
Q

Pethidine

A

Opioid
Analgesia in labour
But relaxes uterus and can cross placenta causing respiratory depression in the neonate
IM
Cannot give repeated doses as norpethidine (metabolite) causes convulsions

34
Q

Opioid agonist/antagonist

A

Action depends on receptor type

All analgesic

35
Q

Pentazocine

A

Opioid agonist/antagonist

Causes dysphoria

36
Q

Nalbuphine

A

Opioid agonist/antagonist

37
Q

Butaphanol.

A

Opioid agonist/antagonist

38
Q

Buprenorphine

A

Opioid agonist/antagonist

39
Q

Meptazinol

A

Opioid agonist/antagonist

40
Q

Opioid antagonists

A

Used in opioid toxicity, respiratory depression and dependence treatment
Mu antagonists - naloxone T1/2 1-1.5 hrs. High affinity so can compete effectively.
Naltrexone T1/2 4 hrs

41
Q

Opioid ADRs

A
GI- vomiting, constipation
Drowsiness
Miosis 
Respiratory depression
Hypotension
Dependence, tolerance
All mu receptor 
K receptor - dysphoria