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Flashcards in Anticogulant Drugs Deck (43):
1

What are you targeting in prevention of venous thrombosis?

Secondary haemostasis

2

What is a natural inhibitor of fibrin clot formation?

Anti thrombin III

3

What does heparin do?

Potentiates antithrombin

4

How long does it take for heparin to work?

Immediate

5

How do you give heparin?

Subcutaneous
Can also be given IV in rare situations

6

Why isn't unfractionated heparin used anymore?

Very narrow theraputic window - LMWH is better

7

How does heparin potentiate antithrombin?

Binds to Antithromibin to stabilise the link between it and thrombin or Xa.

8

What test do you use to monitor heparin?

APTT if unfractionated
Anti Xa assay for LMWH but not really used in clinical practice

9

What test do you do to monitor warfarin?

INR (PT)

10

What other assay is occasionally used in heparin monitoring?

Anti Xa

11

Why is APPT used in heparin monitoring?

APPT much more sensitive to heparin therapy

12

Why do you monitor FBC in heparin?

Risk of Heparin Induced Thrombocytopenia (HITT)
If platelet count drops call haematology

13

Give a long term risk of heparin

Osteoporosis

14

What should you do if you get a low platlet count n someone who is on heparin

- Contact haematology
- Stop heparin
Start other anticoagulant

15

What do you do in the case of bleeding in a patient who is on heparin?

Stop heparin

16

Does heparin have a short of long half life

Short ~ 12 hours

17

What is the antidote to heparin?

Protamine sulphate. This reverses antithrombin effect. Only partially effects LMWH as it does not have an effect on Factor Xa

18

Why does protamine sulphate only partially reverse the effect of LMWH?

Does not have an effect on Factor Xa

19

Where is Vitamin K absorbed?

Upper intestine

20

What dos Vitamin K require for absorption?

Bile salts

21

What clotting factors require Vitamin K?

II
VII
IX
X
Protein C
Protein S

22

What are the first clotting factors to fall when warfarin is started?

Protein C and S

23

Why do you need to have 5 days of initial heparin therapy with warfarin?

Different half lives of the clotting factors

24

How does vitamin K activate clotting factors?

Carboxylation of glutamic acid

25

Where is warfarin metabolised?

Liver - Cytochrome p450 pathway

26

What metabolises warfarin?

Cytochrome p450

27

How do you start warfarin therapy?

Loading high dose with heparin. Monitor closely and then titrate down
If AF and they haven't had a blood clot then start slowly

28

When should warfarin be taken?

At the same time every day

29

What do you use to monitor warfarin therapy?

PT (INR)

30

What is the equation for INR?

PT is seconds/Mean normal PT is seconds x International Sensitivity Index

31

What is the target INR in patients on warfarin?

2 - 3

32

If you have an INR of 5 are you more at risk of bleeding or clotting?

Bleeding

33

What are the side effects of warfarin?

Skin bruising
Epistaxis
Haematuria

34

What is the risk of an intracerebral haemmorhage in people on warfarin therapy?

1/200 per year

35

How do you reverse warfarin therapy?

1. Omit warfarin dose (this will take several days to get INR back into target range)
2. Oral vitamin K (takes about 6 hours)

36

What do you do if the INR is above 8 or if there is significant bleeding in a patient on warfarin?

Give oral vitamin K

37

What do you do if there is severe bleeding in a patient on warfarin?

1. Stop warfarin
2. Oral Vitamin K
3. Clotting factor administration

38

How long does it take for oral vitamin K to work?

6 hours

39

What do you give to reverse warfarin therapy if you need an immediate reversal?

Clotting factors

40

What are the two classes of new anticoagulants?

Oral direct thrombin inhibitors (Dabigatran)
Oral Xa inhibitors (Rivaroxaban)

41

Name a factor Xa inhibitor?

Rivoroxabam

42

What is the advantage of Xa inhibitors over thrombin inhibitors?

Not renally excreted - won't cause kidney injury

43

What kind of drug is rivoroxabam?

Xa inhibitor