15 Prostanoids & NSAIDS Flashcards Preview

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Flashcards in 15 Prostanoids & NSAIDS Deck (92):
1

What are the general reactions catalyzed by phospholipase A2 (PLA-2), cyclooxygenase, and lipoxygenase?

Membrane phospholipids(eg phosphatidylcholine) -> C-20:4 (usually arachidonic acid) by PLA-2
C-20:4 -> prostanoids by cyclooxygenase
C-20:4 -> leukotrienes by lipoxygenase

2

What are eicosanoids?

prostanoid and leukotriene derivatives of C-20 fatty acids

3

Generally what is the function & classification of a cyclooxygenase enzyme?

One that has both cyclooxygenase and peroxidase activity - in the class PGH synthase
Convert arachidonic acid to prostaglandin H (PGH2)

4

Generally, how do the effects of prostacyclin (PGI2) and thromboxane (TXA2) relate to one another?

The are opposite effects.
Prostacyclin has anti-inflammatory effects
Thromboxane has pro-inflammatory effects

5

Which prostanoid has a longer half life?

Prostacyclin (PGI2)

6

In general, what length of half-lives do prostanoids have?
Are their effects local or systemic because of this?
Are they stored?

Short half lives
Local activity
No, not stored (synthesis-dependent, membrane permeable, and passively released)

7

What are the sites of synthesis of each type of prostanoid?

PGE2 & PGF2alpha - most tissues
PGI2 - endothelium and vascular smooth muscle
TXA2 - platelets and macrophages

8

What prostanoid(s) lead(s) to hyperalgesia?

PGI2
PGE2

9

Type 1 & 3 prostanoids are often less/more active that type 2 and are pro/anti-inflammatory?

Less active
Anti-inflammatory
Eg. diets rich in alternative fatty acids could reduce inflammatory and platelet effects of prostanoids

10

of COX 1 & COX 2:
Which is inducible? Which is constitutively expressed?

Cox 1 - not inducible, constitutively expressed
Cox 2 - highly inducible

11

of COX 1 & COX 2:
What is the distribution in tissues?

Cox 1 - all except RBCs
Cox 2 - all except RBCs and platelets

12

T/F
Prostaglindin H (PGH) is the same whether made by COX 1 or COX 2.

True
Prostanoid products of equimolar levels of COX-1 & COX-2 are equivalent in quantity and quality

13

of COX 1 & COX 2:
What substrate(s) are they selective for?
Which is narrow spectrum?

Cox 1 is narrow spectrum - arachidonate
Cox 2 is broader spectrum - arachdisonate, linolenic, unsaturated C22 FAs

14

What effect does prostacyclin (PGI2) have on blood vessels?

dilate blood vessels

15

What effect does prostacyclin (PGI2) have on smooth muscle (except in vessels)? What specific location(s) of smooth muscle?

relax: bronchial, uterine

16

What effect does prostacyclin (PGI2) have on platelets?

inhibits aggregation

17

What effect does prostacyclin (PGI2) have on pain?

hyperalgesia

18

What effect does thromboxane (TXA2) have on blood vessels?

constrict blood vessels

19

What effect does thromboxane (TXA2) have on smooth muscle (except in vessels)? What specific location(s) of smooth muscle?

constrict: bronchial

20

What effect does thromboxane (TXA2) have on platelets?

stimulates aggregation

21

What effect does thromboxane (TXA2) have on pain?

none

22

What effect does PGE2 have on blood vessels?

Gs -> dilate
Gq -> none

23

What effect does PGE2 have on smooth muscle (except in vessels)? What specific locations of smooth muscle?

Gs -> relax GI circular & bronchial
Gq -> constrict GI longitudinal & uterine

24

What receptor does thromboxane (TXA2) bind to?

Gq

25

What receptor does prostacyclin (PGI2) bind to?

Gs

26

What effect does PGE2 have on platelets?

none

27

What effect does PGE2 have on pain?

Gs -> hyperalgesia
Gq -> none

28

At steady state for most cells, which enzyme is more predominate? COX-1 or COX-2?

COX-1

29

Is COX-1 or COX-2 responsible for most "house-keeping" levels of prostanoids in tissues? What organ is the exception?

COX-1
kidney where COX-2 has a role

30

Elevated prostanoid production associated with inflammation is mostly due to _______? (COX-1 or 2?)

COX-2

31

Which enzyme (COX-1 or 2) is responsible for hyperalgesia?

During inflammatory pain, COX-2 is induced in sensory nerve terminals. Hyperalgesic prostaglandins are generated (PGE2 & PGI2).

32

What drug class targets hyperalgesia (reducing inflammatory pain)?

NSAIDs

33

What process is responsible for fever?

IL-1 & TNF-alpha increase COX-2 expression and PGE2 production in the OVLT (organum vasculosum laminae - part of the pre-optic hypothalamus)

34

What drug class targets fever?

NSAIDs

35

Which enzyme (COX-1 or 2) is in platelets?

COX-1

36

What drug class inhibits platelet COX enzyme?
What specific drug irreversibly inhibits?

NSAIDs
Aspirin

37

What is the outcome for aspirin inhibition in a single platelet?

No TXA2 made for the life of the individual platelet

38

Inhibitions of which enzyme (COX-1 or 2) may increase platelet aggregation? Mechanism?

COX-2 contributes to PGI2 production in endothelial cells

39

Which enzyme (COX-1 or 2) and prostanoid (PGE2/PGI2/TXA2) contributes to decreasing acid production and increasing mucus formation in the GI tract?

COX-1
PGE2 in epithelium
PGI2 in vessels

40

What does inhibition of COX-1 do to the GI tract?

increases acid production and decreases mucus production; lysis of epithelium -> ulcers

41

What role does COX-2 play in the GI tract?

GI infections or inflammation induces COX-2

42

What drug can protect against COX-1 inhibition in the GI tract?

misoprostol

43

What effect(s) do COX-1 &/or 2 have in the kidney? A patient with what problems would be of concern for COX inhibition?

Both COX-1 & 2 increase renal blood flow
Critical for maintenance of renal blood flow in compromised patients (CHF, diuretic use, volume depletion, renal insufficiency)

44

Which enzyme(s) (COX-1 or 2) are involved in the uterine cycle?

Both COX-1 & 2 present at various stages of the menstrual cycle and pregnancy

45

Which prostanoids (PGE2/PGI2/TXA2) contribute to functions of the uterus? What function?

PGE2 & PGF2alpha contract uterine smooth muscle
PGI2 relaxes uterine smooth muscle

46

What effect do COX inhibitors have on the uterus?

can delay premature labor and can reduce dysmenorrhea (menstrual cramps)

47

What are the 2 classes of prostaglandin effects?

Prostaglandin class 1 - "house-keeping" physiologic effects
class 2 - inflammation

48

What are the 3 individual functions of class 2 prostaglandins in relation to inflammation?

pain (hyperalgesia) - analgesic action
fever - pyretic action
cell production of, and their response to, some mediators of inflammation

49

COX-1 prostaglandin products are largely associated with which class of prostaglandin?
COX-2?

COX-1 prostaglandin products largely associated with class 1
COX-2 prostaglandin products largely associated with class 2

50

What is the importance of the acetyl group in aspirin?

It is irreversibly transferred to COX-1 & COX-2 (acetylation)

51

What is the chemical structure name of aspirin?
What is the product after aspirin irreversibly inhibits the COX enzymes?

acetyl salicylic acid -> salicylic acid

52

Where are the metabolites of aspirin excreted?

the urine

53

At what mg total does elimination of aspirin saturate?
What does this do to the half life of aspirin in the body?

600mg
increases from 3-5 hours to 12-16 hours

54

What is the selectivity of aspirin for COX enzymes?

Selectivity = 4.4
You need a 4x higher concentration to inhibit of COX-2 relative to what you need to inhibit COX-1

55

What is the formula for COX selectivity?

IC50 COX-2 / IC50 COX-1
eg aspirin:
IC50 COX-1 = 1.7 micromolar
OC50 COX-2 = 7.5 micromolar
7.5/1.7 micromolar = 4.4

56

What effect does aspirin have on COX enzymes?
What about its metabolite?

aspirin acetylates and irreversibly inhibits COX-1 & 2
salicylic acid is a reversible inhibitor of COX-1 & 2

57

What class are these drugs in?
aspirin
ibuprofen
naproxen
acetaminophen
diclofenac
diclofenac with misoprostol
indomethacin
ketorolac

nonselective COX inhibitors (NSAIDs)

58

What class are these drugs in?
celecoxib
rofecoxib

COX-2 selective inhibitors (NSAIDs)

59

What does a drug with a selectivity of much less than 1 indicate for COX enzyme inhibition?

Selective inhibition of COX-2 and (for the most part) not COX-1

60

Which NSAID has a drastically high selectivity for COX-1?

ketorolac

61

What is the common usage for ketorolac?

post-surgical analgesic

62

What is the common usage for indomethacin?

Rx arthritis/anti-inflammatory
high frequency of intolerance

63

What is the common usage for aspirin?

OTC analgesic/antipyretic
cardiovascular prophylaxis

64

What is the common usage for naproxen?

OTC analgesic/antipyretic
Rx anti-inflammatory

65

What is the common usage for ibuprofen?

OTC analgesic/antipyretic

66

What is the common usage for diclofenac?

Rx arthritis/anti-inflammatory

67

What is the mechanism of anti-inflammatory effects of NSAIDs?

block production of prostanoids by inhibition of COX
mainly COX-2 responsible for inflammation

68

What is the mechanism of antipyretic effects of NSAIDs? When will NSAIDs not influence body temperature?

inhibit PGE2 production in the CNS stimulated by IL-1 & TNF-alpha. reduced peripheral prostanoids may also reduce IL-1 expression from macrophages
will NOT influence body temperature when elevated by non-inflammatory factors

69

1- What is the mechanism of analgesic effects of NSAIDs?
2- What are NSAIDs not effective against?

1- reduction of PGE2 and PGI2-induced hyperalgesia
general reduced inflammation
2- not effective against non-inflammatory pain

70

What class of drugs is usually more efficacious than NSAIDs in analgesic effects?

opioids

71

What are the effects of NSAIDs on platelets? What is the result?

inhibition of platelet COX-1 -> increased bleeding time

72

What effect does aspirin have on platelets? Why?

aspirin acetylation of COX-1 is irreversible, so inhibition lasts the life of the platelet (5-7 days)

73

What is the mechanism of gastric effects of NSAIDs?

Reduced PGE2 and PGI2 lessens gastric protection -> can induce peptic ulcers

74

What are the 5 therapeutic applications of NSAIDs?

- fever
- analgesia (mild to moderate pain)
- mild to moderate inflammation due to injury/stress
- rheumatoid and osteoarthritis (analgesia and chronic inflammation reduction)
- cardiovascular prophylaxis (aspirin ONLY)

75

What is Salicylism?
Signs/symptoms?

hypersensitivity to aspirin
hyperventilation, tinnitus (ringing ears), vertigo, emesis, sweating

76

What is Reye's Syndrome?

acute encephalopathy and fatty liver degeneration linked with aspirin use in children with viral illness
associated with viral disease and antiviral vaccines

77

NSAIDs cause what 3 major adverse GI effects? What percentage of chronic NSAID users may require treatment?

Dyspepsia - upper abdominal pain, bloating, nausea (35% chronic NSAID users may require treatment)
Ulcers - gastric ulcer more frequent than duodenal ulcer (16% chronic NSAID users)
GI bleeding - anemia

78

What condition is associated with these risk factors?
Age >65
chronic NSAID use
concomitant steroids, other NSAIDs
high dose
H. pylori infection
alcohol consumption

gastric ulcer

79

What 3 drug classes can help prevent the adverse GI effects of NSAIDs?

H2-receptor antagonists
Proton pump inhibitors
Misoprostol

80

Patients with what problems are at risk for renal complications with NSAID use?

-CHF
-Cirrhosis/ascites
-Advanced age
-Patients chronically taking NSAID combinations or an NSAID plus acetaminophen

81

What are the adverse renal effects from NSAID use?

Renal vasoconstriction, water and salt retention -> edema, hypertension, renal failure
Acute renal failure (0.5-1% of chronic NSAID users)

82

What are the adverse effects of NSAID platelet effects?

increased surgical bleeding
potentiates GI bleeding resulting from gastric erosion ulceration

83

What are the effects of COX-2 selective NSAIDs? How are they different from the NSAID class as a whole?

Selectively inhibits COX-2 compared to COX-1 (more than 10-fold)
Retain the COX-2 specific effects:
-anti-inflammatory effects
-antipyretic effects
-analgesic effects
-renal toxicity effects
Lack the COX-1 specific effects:
-platelet and cardio-protective effects
-GI side effects

84

COX-2 selective NSAIDs are mainly used to treat what 2 problems?

osteoarthritis
rheumatoid arthritis

85

What are the specific effects of acetaminophen?

-relatively non-selective COX inhibitor
-activity substantially reduced in presence of peroxides (often elevated at sites of inflammation)
-lacks significant effects on platelets, cardiovascular, and GI systems
-analgesic and antipyretic effects equivalent to aspirin

86

What is acetaminophen used to treat? (analgesic/antipyretic/anti-inflammatory/etc)

Analgesic & antipyretic only
negligible anti-inflammatory activity

87

What organ toxicity is a concern with acetaminophen overdose?

hepatotoxicity

88

What is the COX selectivity of celecoxib?

10-20x more selective for COX-2 than 1

89

What is the COX selectivity of rofecoxib?

200x more selective for COX-2 than 1

90

What are the results from clinical trials of COX-2 selective NSAIDs:
Adverse effects?
Still on the market?

Adverse effects:
increased incidence of cardiovascular events: hypertension, heart attack, stroke (associated with long-term continuous use)

On market?
rofecoxib - withdrawn
celecoxib - remains available despite evidence of risk

91

T/F
Data shows that ALL NSAIDs appear to be associated with some level of increased risk of cardiovascular event.

False. all except aspirin

92

What is the possible mechanism of NSAIDs relating to cardiovascular risk?

loss of COX-2 dependant antagonism of platelet activity