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Semester 2 Molecular Medicine > NSAIDS > Flashcards

NSAIDS Flashcards

1
Q

What are the 3 properties of NSAIDs?

A
  • Anti-inflammatory
  • Anti-pyretic
  • Analgesic
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2
Q

What is the primary action of NSAIDs?

A

They inhibit prostaglandin biosynthesis by action on cyclo-oxygenase enzymes

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3
Q

What are the 2 mechanisms of inhibition of the COX enzyme?

A
  • Irreversible, time dependent inhibition

* Reversible, competitive inhibition

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4
Q

Describe the time dependent inhibition of the COX receptor in relation to an example

A
  • Aspirin
  • Inactivates the enzymes
  • Aspirin acetylates the alpha amino group of the terminal serine on the enzyme forming a covalent bond
  • Further synthesis of prostaglandin requires synthesis of a new enzyme
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5
Q

Describe the rapid reversible inhibition of the COX receptor

A
  • Ibuprofen
  • Binds reversibly to the enzyme
  • Competes with natural substrate arachidonic acid
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6
Q

How are prostaglandins generated?

A

In their precursor form- arachidonic acid, by cyclooxyrgenase enzymes

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7
Q

What are the products from arachidonic acid metabolism?

A
  • Thromboxanes
  • Prostaglandins
  • Leukotrienes
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8
Q

Describe COX-1

A
  • Constitutive (constantly produced)

* Important in the maintenance of GI tract integrity

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9
Q

Describe COX-2

A
  • Inducible
  • Involved in the inflammatory response
  • Implicated in cancer development
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10
Q

What is inflammation always accompanied by?

A
  • The release of prostaglandins
  • Predominantly PGE2 but also PGI2
  • PGD2 from mast cells
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11
Q

Describe the effect of PGE2, PGD2 and PGI2

A
  • Potent vasodilators
  • Synergise with other inflammatory mediators e.g. histamine and bradykinin
  • Potentiate histamine and bradykinin actions of post capillary venue permeability and pain sensory nerves
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12
Q

Describe the anti-inflammatory properties of NSAIDs

A

Prostaglandins cause vasodilation and resultant oedema
• They have less effect on cellular accumulation or migration
• Therefore they only affect aspects in which prostaglandin splay a significant part
• Can reduce many of the local signs and symptoms of inflammation: redness, swelling, heat, pain

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13
Q

Describe the anti-pyretic properties of NSAIDs

A
  • Body temperature is regulated by the hypothalamus
  • Fever when the hypothalamic thermostat ‘set point’ is raised
  • Bacterial endotoxins release factors (Interleukin 1) from macrophages
  • IL-1 causes the generation of prostaglandins in the hypothalamus
  • Prostaglandins increase the thermostat set point
  • Therefore by preventing the formation of prostaglandins, they prevent temperature rise
  • Don’t affect the normal body temperature
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14
Q

Why do some inflamed regions become painful?

A

Bradykinin and histamine release
• Activate nocioceptive afferent nerve terminals
• Register painful stimulus
Prostaglandins sensitise the nocioreceptive nerves to these compounds

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15
Q

Describe Salicylates

A

• Aspirin family
Aspirin:
• Pro drug
• Can directly acetylate the COX enzyme
• Metabolised to its active form (salicylic acid) by plasma and tissue esterases
• Salicylates found in the plasma within 30 minutes
• Peak plasma concentration is within 1-2 hours

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16
Q

What are the unwanted side effects of salicylates?

A
  • Stomach: Bleeding and ulcers
  • Systemic: Dizziness, nausea, vomiting, impaired hearing, tinnitus
  • Metabolic changes: acid/base balance effected
  • Haemostasis: Blood coagulation affected
  • CNS: stimulation initially then coma and respiratory depression
  • Renal: Insufficiency in susceptible patients with chronic use and overdose
17
Q

Describe propanic acids

A
  • e.g. Ibuprofen, naproxen
  • Not prodrugs
  • Well absorbed
  • 4-6 hours
18
Q

Give an example of a fenmate

A

Mefenamic acid

19
Q

Describe paracetamol

A
  • Good analgesic and anti-pyretic
  • Poor anti-inflammatory
  • Well tolerated in the gastrointestinal system
  • Weak COX inhibitor
  • Given orally and well absorbed
  • Fewer side effects than the NSAIDs
20
Q

When is peak plasma concentration for paracetamol?

A

30-60mins

21
Q

What is paracetamol’s half life in the plasma?

A

2-4 hours

22
Q

What is the major issue with paracetamol?

A
  • Hepatotoxicity due to overdose
  • Normally inactivated in the liver by glucoronate and sulphate conjugation
  • When these are saturated, toxic metabolites are formed
  • Result can be hepatic necrosis
23
Q

What is an example of a selective COX 2 inhibitor?

A

Coxibs e.g. celecoxib

24
Q

What are COX 2 inhibitors used for?

A
  • Osteoarthritis
  • Rheumatoid arthritis
  • Restricted for when traditional NSAIDs produce too severe GIT side effects
25
Q

What needs to be assessed before prescribing a patient COX 2 inhibitors?

A

Cardiovascular risk

26
Q

What are the short term analgesics?

A
  • Aspirin
  • Paracetamol
  • Ibuprofen
27
Q

What are the longer lasting analgesics?

A
  • Naproxen

* Diclofenac

28
Q

For use as an anti-pyretic, why is paracetamol preferred?

A

Lacks GIT side effects

Semester 2 Molecular Medicine (27 decks)

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