NSAIDs Flashcards

1
Q

What is pain?

A

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

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2
Q

What is allodynia?

A

pain due to stimulus which does not normally provoke pain

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3
Q

What is hyperalgesia?

A
  • increased response to stimulus which is normally painful
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4
Q

What are the types of chronic pain? (and examples)

A
  • nociceptive = receptors from site of injury to CNS (OA and RA)
  • neuropathic = initiated by primary lesion or dysfunction in nervous system (central or peripheral)
  • visceral = involves internal organs (IBS)
  • mixed pain = various origins (lower back, fibromyalgia)
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5
Q

What is somatic pain?

A
  • aching, often constant
  • dull or sharp
  • worse with movement
  • localised except when deep (muscle, tendon, ligament, bone, fascia and joints)
  • OA pain
  • Hilton’s Law
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6
Q

What is the WHO analgesic ladder?

A

1) NSAIDs, non-opoid analgesics
2) + weak opoids
3) + strong opoids (methadone), oral admin., transdermal patch
4) + nerve block, epidurals, neurolytic block therapy, spinal stimulation

(may start higher up or from top then go down with acute pain, up ladder with chronic pain)

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7
Q

What are NSAIDs used for?

A
  • analgesic for inflammation

ibuprofen, aspirin, COX2 inhibitors, diclofenac plus many others

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8
Q

What is the mechanism of action of aspirin?

A
  • COX1 and COX2 inhibitor

- analgesic, antipyretic and anti-inflammatory

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9
Q

What is the mechanism of action of ibuprofen, diclofenac and ketoprofen?

A
  • COX1 and COX2 inhibition

- analgesic and anti-inflammatory

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10
Q

What are the selective COX2 inhibitors?

A

rofecoxib, celecoxib, etroicoxib and meloxicam

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11
Q

What happens if COX is inhibited in the stomach?

A
  • decreased mucus secretion
  • decreased bicarbonate secretion
  • decreased blood flow
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12
Q

How is there an increased CV risk with COX1 inhibitors?

A
  • related to strokes
  • COX1 inhibition = increased vasoconstriction = aggregation of platelets
  • rofecoxib, diclofenac, ibuprofen and celecoxib
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13
Q

What is the COX3 controversy?

A
  • transcribed from COX-1 gene
  • hypothesised as target for paracetamol
  • appears non-functional in humans
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14
Q

What is the mechanism of action of paracetamol?

A
  • does not inhibit COX outside of CNS
  • modulates cannabinoid system
  • activates serotonergic descending pathways
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15
Q

What is the difference between acute and chronic pain?

A

Chronic lasts longer than 12 weeks/3 months

Acute is a response to injury/post operative flare, diminishes with tissue healing

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16
Q

What does Hilton’s law state?

A

nerves supplying muscles which move the joint also supply that joint capsule and skin over joint

  • so somatic pain is quite localised
  • problem when muscle groups working over 2 joints (hip and knee) so could be problem in either
17
Q

What is the role of COX1 and COX2?

A
  • take arachidonic acid and produce PG, PC and thromboxanes
18
Q

What is the difference between acute and chronic pain?

A

Chronic lasts longer than 12 weeks/3 months

Acute is a response to injury/post operative flare, diminishes with tissue healing

19
Q

What does Hilton’s law state?

A

nerves supplying muscles which move the joint also supply that joint capsule and skin over joint

  • so somatic pain is quite localised
  • problem when muscle groups working over 2 joints (hip and knee) so could be problem in either
20
Q

What is the role of COX1 and COX2?

A
  • take arachidonic acid and produce PG, prostacyclin and thromboxanes
  • prostacyclin = hyperalgesia by making nerve endings more sensitive, stop platelet aggregation, vasodilation
  • thromboxanes = thrombotic and vasoconstrictors
  • prostaglandins = vasodilators, inhibit platelet aggregation, hyperalgesic
21
Q

Difference between COX1 and COX2?

A
  • COX1 narrower and more rigid
  • COX2 wider
  • arachidonic acid fits into hydrophobic channel
  • COX1 is housekeeping genes, constituent, homeostasis role, GI tract/renal/platelet/macrophage differentiation, low levels, local, constant low level production of PG in these areas
  • COX2 inducible, different gene, hydrophobic channel sticks out = less rigid, only in damaged tissue and spinal cord and CNS, high quantities, quick gene activation, larger active site, rate of consumption of arachidonic acid is greater making more PG quicker
  • COX2 increased in OA and RA joints
22
Q

What are the properties of PG?

A
  • tissue hormone
  • do not diffuse far so act on local cells/tissues which produce them
  • CLASSES = D,E,F classes, prostacyclin
    , thromboxane A
  • work via GPCR (9 of them, prostanoid/PG receptors)
23
Q

What does PGE2 do?

A
  • vasodilation of renal artery
  • suppresses lymphocytes
  • sensitises peripheral nerve endings
  • inhibits gastric acid secretion
  • fever
  • uterine relaxation
24
Q

What does PGD2 do?

A
  • vasodilation

- bronchoconstriction (higher is asthmatics)

25
Q

What does PGI2 do?

A
  • vasodilation of renal artery
  • inhibit platelet aggregation
  • bronchodilation
  • inhibit gastric acid secretion
  • sensitise afferent nerve endings to pain
26
Q

What does PGF2alpha do?

A
  • vasodilation and dilation
  • bronchoconstriction
  • uterine contraction
27
Q

What does TXA2 do?

A
  • vasoconstriction
  • induces platelet aggregation
  • bronchoconstriction
  • uterine contraction
28
Q

What is iNOS?

A
  • inducible NO synthase
  • pro-inflammatory cytokines directly or indirectly (via iNOS) induce COX2
  • in OA and RA = COX2 effects
29
Q

What is the role of COX in the stomach?

A
  • mainly COX1
  • in crypts protecting against injury and damage
  • PGE2 helps gastric muscosa
  • low COX2 levels in superficial mucosa
  • LT oral NSAID use blocks PGE2 = GASTRITIS, gastric ulcers
  • instead give COX2 inhibitor only or topical use (diclofenac) so concentrated in joint bypassing stomach
30
Q

How does aspirin work?

A
  • binds to COX1 in platelets and forms covalent change to active site so platelet unable to ever become activated = blood thinner
31
Q

Why should ibuprofen and aspirin not be used in conjunction?

A
  • blocks the active site of COX1 for a short period of time

- also blocks aspirin from getting in there so aspirin works less effectively when used with ibuprofen

32
Q

What is the role of COX in the kidney?

A
  • PG vasodilation of afferent arteriole = increased blood flow through glomerulus = normal GFR
  • if inhibit = less flow through kidney = reduced GFR
  • PGE2 regulates sodium absorption and I2 regulates potassium excretion = bp control
  • COX2 in small amounts in macula densa, increased in salt deprivation
33
Q

What are the main 3 NSAID modes of action?

A
  • rapid competitive reversible binding of COX1/2 (ibuprofen, acute pain management, analgesic and anti-inflammatory)
  • rapid reversible binding followed by covalent modification of COX1 and/or COX2 non competitive irreversible (aspirin, acute pain management, blood thinner)
  • rapid lower affinity reversible binding followed by time dependent high affinity slow reversible COX1/2 binding (diclofenac, chronic pain)
34
Q

What does NSAID effect depend on?

A
  • COX2 inhibition