Anticoagulants/Antiplatelets Flashcards Preview

Sem 5 Pharm > Anticoagulants/Antiplatelets > Flashcards

Flashcards in Anticoagulants/Antiplatelets Deck (37):
1

Warfarin is metabolised how?

Hepatic metabolism- by CYP450 enzyme

2

What is Warfarins distribution once absorbed?

Heavily protein bound to albumin 99%

3

What drugs would increase the conc of warfarin in the blood? (2 mechanisms)

By displacing warfarin bound to albumin- NSAIDs
By inhibiting CYP450- cimetidine, amiodarone, alcohol, metronidazole

4

How long is Warfarins onset of action?

Slow and so may need heparin to cover initially

5

How fast or slow is Warfarins offset?

Half life ~48 hrs
Therefore need to stop 3 days prior to surgery to allow for making of new clotting factors

6

Side effects of Warfarin

Bleeding, epistaxis, GI bleeding, intracranial

7

How can you reverse warfarin?

Parenteral vitamin K (acts slowly)
Fresh frozen plasma (acts quickly)
Can also give Prothrombin Complex Concentrate (ii, ix, x)

8

What cautions do you need to be wary of with warfarin?

Teratogenic in 1st trimester
Can cause brain haemorrhage in 3rd trimester

9

What is INR?

Patients prothrombin time OVER average prothrombin time

10

Which common drugs should be avoided in warfarin use?

Antiepileptics
St Johns Wort
Rifampicin

(All induce hepatic enzymes)

11

Mechanism of action of warfarin?

Vitamin K antagonist.
Vitamin K is needed for the production of active factors II, VII, IX, X

12

What is Virchow triad?

Hypercoaguability
Blood stasis
Endothelial damage

13

Mechanism of action of heparin

Binds reversibly to anti-thrombin therefore
Almost instant inactivation of factors IIa, Xa
Therefore prevents progression of existing clots

14

Name two examples of a LMWH

Dalteparin
Enoxaparin

15

Give three advantages of LMWH over unfractionated

Absorbed better/better absorption predictability
Higher bioavailability (90%)
More predictable dose response curve

16

Name three negatives of unfractionated heparin

Non linear dose response curve
Poor absorption from gut therefore needs to be IV or SC
Can’t be eliminated in haemodialysis

17

Name three adverse drug reCtions of unfractionated heparin

Bruising/bleeding
Osteoporosis
Thrombocytopenia (immune phenomenon)

18

How can you reverse heparin?

Stop the heparin asap
Use Protamine Sulfate (dissociates the heparin from the antithrombin)

19

Name an advantage of LMWH over warfarin

Is safe to use in pregnancy

20

Name three DOACs

Rivoroxaban
Apixaban
Dabigatran

21

What is the mechanism of action of Rivoroxaban

Competitive antagonist of factor Xa

22

What is the mechanism of action of Dabigatran

Competitive antagonist of Thrombin

23

Name a positive of DOACs

No monitoring required
No antidote available
Have more predictable pharmacokinetics

24

Name one drug you should avoid while taking Dabigatran

PPI
they reduce absorption

25

How are DOACs excreted?

Renal
Therefore in renal exposure, you will get increased drug exposure

26

Name three anti-platelet drugs

Aspirin
Clopidogrel
Dipyridamole

27

Mechanism of action of aspirin

Irreversibly binds to COX enzyme
COX produces pro-inflammatory prostaglandins and thromboxanes
Thromboxanes facilitate platelet aggregation

28

Side effects of aspirin

Bronchospasm
GI upset
Hypersensitivity reactions

29

Contraindications of aspirin

Asthma
Peptic ulcer
If pt has hypersensitivity to NSAID

30

Mechanism of action of clopidogrel

Prevents binding of ADP to platelet receptor which stops the cross linking of fibrin

31

How is clopidogrel metabolised?

Clopidogrel is a pro drug that is metabolised by CYP450 to become active.
Then metabolised by the liver

32

Side effects of clopidogrel

Abdo pain
Diarrhoea
Dyspepsia
Bleeding disorder

33

How is clopidogrel excreted

50% renal, 50% excreted

34

What is the half life of aspirin

15 minutes but then increases as the dose increases

35

Mechanism of action of dipyridamole

Adjunct to other antiplatelets
Phsophodiesterase inhibitor, prevents breakdown of cAMP, cAMP usually inhibits platelet function.

36

Metabolism of dipyridamole

Hepatic and excreted with bile

37

Side effect of dipyridamole

Positive inotrope and vasodilator(tf flushing and headaches)