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Flashcards in NSAIDs Deck (39)
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1
Q

What are autocoids

A

Autocoids are local inflammatory mediators in acute inflammation (acute response to noxious stimuli)

bradykinin, histamine, leukotriene, prostaglandins

They act locally with short T1/2 - can be finely controlled
Their signalling pathways overlap - robust inflammatory response

2
Q

What are prostaglandins

A

Type of autocoids synthesised from Arachidonic acid

3
Q

How are prostaglandins synthesised

A

From arachidonic acids by COX enzymes:
Cell membrane Phospholipid to Arachidonic acid by phospholipase A
Arachidonic acid to PG H by COX 1 or COX2
PG H to PG E/F/I/D by specific PG enzymes
PG E most important in Inflammation

4
Q

What are COX enzymes

A

Enzymes involved in synthesis of prostaglandins from arachidonic acid

5
Q

What are the differences in COX1 and COX2 enzymes

A

COX1: constitutively expressed
COX2: only active in inflammation, expression is induced by inflammatory mediators

Different binding site for NSAIDs

6
Q

What is the role of COX1

A

Produce PGs constantly in normal state to allow vasodilation and perfusion of tissues in: GI mucosa, renal parenchyma, myocardium

7
Q

What is the effect of COX1 inhibition

A

Side effects of NSAIDs

Prostaglandins are required in normal state but have short half life so need to be constantly produced by COX1

8
Q

What is the role of COX2

A

Produce PGE in inflammation

9
Q

What is the effect of COX2 inhibition

A

Therapeutic effect of NSAIDS

Anti inflammatory, antipyrexial, analgesia

10
Q

What is the mechanism of action of PGs in inflammation

A

Pyrexia, inflammation and pain sensitisation by acting on GPCRs

11
Q

What is the process of peripheral nociceptor sensitisation

A

PGE bind to EP1 GPCR receptor on C fibre neurones
Increase neuronal sensitivity to bradykinin
Activate Na channels, inhibit K channels
Increase excitability of C fibres
Cause hyperalgesia: increased sensitivity to pain

12
Q

What is the process of central nociceptor sensitisation

A

Sustained peripheral pain signalling cause cytokine release in dorsal horn cell body
Cytokines increase COX2 activity and PGE
PGE bind to EP2 GPCR
Remove glycinergic inhibition by inhibitory interneurones
Increase sensitivity of secondary pain fibres
Allodynia: perceive pain to stimuli that normally doesn’t cause pain

13
Q

What is the process of pyrexia

A

Macrophages release IL-1 in inflammation
IL-1 act on hypothalamus to produce PGE
PGE act on EP3 GPCR in hypothalamus
Increase heat production and decrease heat loss

14
Q

What is mechanism of action of NSAIDs

A

Competitive inhibition of COX1/2 enzymes

15
Q

What are PK properties of NSAIDs

A

Administration: oral, topical
T1/2: <6 hours or >10hours
Linear PK
Heavily bound to plasma proteins

16
Q

What are the main effects of NSAIDs

A

Anti inflammatory
Analgesia
Antipyrexial

17
Q

What are indications of NSAIDs

A

Inflammatory joint disease
Mild to moderate pain - isolation
Severe pain with opioids - acts as Opioid-sparing agent (better adr profile, extended therapeutic range than in isolation)

18
Q

What are the main side effects of NSAIDs

A
GI
Nephrotoxicity 
Vascular 
Hypersensitivity 
Reye’s syndrome
19
Q

What are the GI side effects of NSAIDs

A

Peptic ulcer disease, UGI Bleeding, gastritis, nausea, heartburn, abdominal pain

20
Q

How can you offset GI side effects

A

PPI

Misoprostol (PGE derivative - when Hx of PUD but NSAID cannot be stopped)

21
Q

Why do GI side effects occur

A

Non-selective inhibition of COX1
Inhibit constitutive synthesis of PGE in GI mucosa
Loss of cytoprotective effects: bicarbonate and mucus production, vasodilation

22
Q

What are renal side effects

A

Na retention

Renal failure

23
Q

Why do renal side effects occur

A

Non-selective inhibition of COX1 enzymes
Inhibit constitutive production of PG in medulla + glomeruli
PG normally cause Na excretion, AA vasodilation

24
Q

Which patients are more at risk of nephrotoxicity from NSAIDs

A
Hepatic cirrhosis (hepatorenal Syndrome)
Renal disease (preexisting poor renal function) 
Heart failure (poor renal perfusion)
25
Q

What are the vascular side effects

A

Increased bleeding time, bruising, haemorrhage

26
Q

What causes vascular side effects

A

Aspirin inhibits thromboxane A2 synthesis thus inhibits platelet aggregation

27
Q

What are the hypersensitivity side effects

A

Skin rash

Bronchial asthma - caution in asthmatics

28
Q

What is Reye’s syndrome

A

Encephalopathy associated with aspirin use after a viral infection in children, involving serious liver and brain injury

29
Q

What drug interactions can occur with NSAIDs

A
Heavily protein-bound Drugs: 
Wafarin - bleeding
Sulphonylurea - hypoglycaemia 
Methotrexate - serious SEs
Other NSAIDs - e.g. reduced antiplatelet action of aspirin
30
Q

What is aspirin

A

Type of NSAID, salicylic acid derivative

31
Q

What is the mechanism of action of aspirin

A

Irreversibly bind to COX enzymes
(the only NSAID to irreversibly bind)
Inhibit thromboxane A2 synthesis
Inhibit platelet aggregation

32
Q

What are the indications for aspirin

A

Athero-thrombotic disease: MI, Stroke
Pain
GI/Breast cancer prophylaxis (on trial, cancer cells produce PGE for growth)

33
Q

What type of drug is paracetamol

A

Non-NSAID non-opioid analgesic

34
Q

What are the therapeutic effects of paracetamol

A

Analgesia
Antipyretic
NOT anti inflammatory

35
Q

What are indications for paracetamol

A

Agent of choice for mild-moderate pain and fever:
Effective
Better ADR profile than NSAIDs

36
Q

What are the PK properties of paracetamol

A

1st order kinetics at therapeutic dose
0 order kinetics at higher dose
Unknown mechanism of action

37
Q

What is the normal metabolism of paracetamol

A

90% metabolised by Phase II Conjugation with glucoronide or sulphate
10% metabolised by Phase I Oxidation to NAPQI and Phase II conjugation with glutathione

38
Q

What occurs in paracetamol overdose

A

First step Phase II metabolism saturated
Increased production of NAPQI - directly hepatotoxic
Second step Phase II metabolism saturated W Glutathione depletion
Build-up of NAPQI
Liver damage, liver necrosis

39
Q

How do you treat paracetamol overdose

A

0-4 hours since ingestion: Oral activated charcoal to reduce GI uptake
<36 hours since ingestion: IV acetylcysteine (replaces glutathione)
At stare of encephalopathy: liver transplantation (irreversible liver damage has occurred)