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Medicine Year 1 - Semester 2 - Part 2 > NSAIDS > Flashcards

NSAIDS Flashcards

1
Q

State the main actions of NSAIDs

A
  1. Anti-inflammatory
  2. Analgesic
  3. Anti-pyretic
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2
Q

Primary action of NSAIDs

A

Inhibit prostaglandin biosynthesis by direct action on cyclo-oxygenase enzymes.

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3
Q

Describe the mechanism of action of NSAIDs

2 main mechanisms of action

A

All inhibit cycle-oxygenase (COX) by 2 main mechanisms :

  1. An irreversible, time-dependent inhibition of the enzyme
  2. A rapid, reversible competitive inhibition of the enzyme
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4
Q

Example of irreversible, time-dependent inhibition of the enzyme

A

Aspirin

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5
Q

Describe the action of aspirin

A

Inactivates the enzyme

Aspirin acetylates the alpha-amino group of the terminal serine of the enzyme forming a covalent bond.

Further synthesis of prostaglandins requires synthesis of new enzyme.

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6
Q

Example of a rapid, reversible, competitive inhibition of the enzyme

A

Ibuprofen

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7
Q

Describe the method of action of ibuprofen

A

Binds reversibly to the enzyme

Competes with natural substrate - arachidonic acid

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8
Q

Describe prostaglandins

A

Family of compounds - PGE2 and PGF2a

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9
Q

How are prostaglandins formed ?

A

Generated in tissues from a precursor (arachidonic acid) by cycle-oxygenase enzymes.

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9
Q

State the 2 main cyclo-oxygenase enzymes

A

COX-1
COX-2

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10
Q

State the products of arachidonic acid metabolism

A

Thromboxanes
Prostaglandins
Leukotrienes

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11
Q

Describe COX-1

A

Constitutive (always present)

Important in maintaining GIT (gastro-intestinal) integrity

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12
Q

Describe COX-2

A

Inducible

Involved in inflammatory response

Implicated in cancer development

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13
Q

Role of prostaglandins in inflammation

A

Inflammation is always accompanied by the release of prostaglandins.

  • Predominantly PGE2 and PGI2
  • PGD2 from mast cells
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14
Q

Function of PGE2, PGI2 and PGD2

A

Acts as potent vasodilators

Also synergise with other inflammatory mediators

Potentiate histamine and bradykinin actions on post capillary venue permeability and pain sensory nerves.

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15
Q

Key function of prostaglandins

A

Mediators of inflammation

  • particularly vasodilation and resultant oedema
  • less effect on cellular accumulation or migration
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16
Q

Inflammatory mediators

A

Histamine
Bradykinin

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17
Q

Describe the anti-pyretic effects of NSAIDs

A

NSAIDs act by preventing the formation of prostaglandins and prevent the rise in temperature.
- no effect on normal body temperature

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18
Q

Describe prostaglandins role in body temperature

A

Body temp regulated by hypothalamus

  • fever occurs when hypothalamic thermostat is raised
  • bacterial endotoxins cause release of factors from macrophages
  • Interleukin 1 causes generation of prostaglandins in hypothalamus
  • Prostaglandins increase the thermostat set point
19
Q

Describe the analgesic effect of NSAIDs

A

By preventing prostaglandin production, NSAIDs prevent sensation to pain-producing compounds.

20
Q

Describe prostaglandins role in pain production

A

Inflamed regions painful due to histamine and bradykinin release

  • activate nociceptive afferent nerve terminals
  • register a painful stimulus

Prostaglandins sensitise nociceptive nerves to these compounds

21
Q

State some NSAID drugs

A

Salicylates - aspirin family

Propionic acids and fenamates

Paracetamol - acetaminophen

Coxibs

22
Q

Mechanism of action of salicylates - aspirin

A

Pro-drug (acetylsalicylic acid) can directly acetylate COX enzyme

Also metabolised to active compound (salicylic acid) by plasma and tissue esterase.

23
Q

Duration of action of aspirin

A

Salicylates found in plasma within 30 minutes.

Peak plasma concentrations within 1-2 hours

24
Q

Side effects on the stomach of salicylates

A

Bleeding, Ulcers

25
Q

Systemic side effects of salicylates

A

Tinnitus
Dizziness
Impaired Hearing
Nausea
Vomiting
Hypersensitivity

26
Q

Metabolic changes - side effects of salicylates

A

Acid/Base balance affected

27
Q

Haemostatic side effects of salicylates

A

Blood coagulation affected through and action on platelets

28
Q

CNS side effects of salicylates

A

Stimulation initially, ultimately coma and respiratory depression

29
Q

Renal side effects of salicylates

A

Insufficiency in susceptible patients and with chronic use and overdose

30
Q

Describe some features of propionic acids

A
  • not prodrugs
  • Well absorbed
  • Lasts for 4-6 hours
31
Q

Give an example of propionic acids

A

Ibuprofen, Naproxen

32
Q

Give an example of a fenamate

A

Mefenamic acid

33
Q

State some features of paracetamol

A
  • Good analgesic and anti-pyretic activity
  • Poor anti-inflammatory
  • Well tolerated in GI tract
  • Weak COX inhibitor
34
Q

Feature of paracetamol - COX related feature

A

Weak COX inhibitor

  • May be selective inhibitor of CNS-specific COX, COX-3
35
Q

Describe the duration of action of paracetamol

A

Given orally

  • Peak plasma concentration 30-60 mins
  • t1/2 in plasma 2-4 hours for therapeutic doses
36
Q

Comparison between paracetamol and other NSAIDs

A

Paracetamol has fewer side effects than other NSAIDs

Due to selectivity for COX enzymes

37
Q

Issue with paracetamol

A

Hepatotoxicity due to overdose

  • Normally inactivated in the liver by glucoronate and sulphate conjugation
  • When these enzymes saturated, toxic metabolites are formed
  • Result can be hepatic necrosis
38
Q

Selective COX-2 inhibitors

A

Coxibs

e.g. Celecoxib

39
Q

What are selective COX-2 inhibitors used for ?

A

Used for osteoarthritis and rheumatoid arthritis

40
Q

When are selective COX-2 inhibitors used ?

A

Restricted for when traditional NSAIDs produce too severe GI tract side effects

Cardiovascular risk needs to be assessed

41
Q

Uses of NSAIDs for analgesia

A

Headache
Backache
Bony metastases of cancer
Postoperative pain
Dysmennorhea

42
Q

Clinical uses of NSAIDs

A

Analgesia
Anti-inflammatory actions
Anti-pyretic actions

43
Q

Short-term analgesia

A

Aspirin
Paracetamol
Ibuprofen

44
Q

Longer-lasting drugs for chronic pain

A

Naproxen
Diclofenac

45
Q

Uses of NSAIDs for anti-inflammatory actions

A

Both chronic or acute inflammatory actions

Dosage for chronic inflammatory disorders is high

Coxibs sometimes used for osteoarthritis and rheumatoid arthritis

46
Q

Uses of NSAIDs as an anti-pyretic

A

To lower temperature

Paracetamol is preferred, as it lacks GI tract side effects

Medicine Year 1 - Semester 2 - Part 2 (53 decks)

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