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Haematology Week 2 2018/19 > 5: Anticoagulant drugs > Flashcards

5: Anticoagulant drugs Flashcards

1
Q

Which clotting times are used to monitor

a) warfarin
b) heparin

activity?

A

a) INR (which is a standardised method of measuring PT)
b) APTT

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2
Q

What are two indications for anti-coagulant drugs?

A

Venous thrombosis

Atrial fibrillation (increases likelihood of thrombosis)

Thrombophilia

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3
Q

Atrial fibrillation can cause (venous / arterial) thrombosis.

A

either

depending on heart chamber where the blood clots

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4
Q

What blood components are activated in

a) venous thrombosis
b) arterial thrombosis?

A

a) Fibrin

b) Platelets

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5
Q

Because of their short half life, Protein C and S levels drop first when a patient is given anticoagulant drugs.

What is the effect of this?

A

Increased risk of thrombosis (temporary)

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6
Q

Which anticoagulant drug enhances the activity of antithrombin?

A

Heparin

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7
Q

What are the two forms and routes of administration of heparin?

A

Unfractionated heparin (IV)

LMWH (subcut)

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8
Q

Name an example of LMWH?

A

Dalteparin sodium

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9
Q

Heparin enhances the activity of ___.

A

antithrombin

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10
Q

Heparin potentiates the activity of antithrombin, a protein which inactivates clotting factors.

Unfractionated heparin enhances the activity of antithrombin against ___.

LMWH enhances the activity of antithrombin against ___.

A

unfractionated: thrombin

LMWH:Xa

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11
Q

Which anticoagulant drugs are monitored using

a) INR
b) APTT?

A

a) Warfarin

b) Heparin

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12
Q

Which clotting time is used to monitor the activity of unfractionated heparin?

A

APTT

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13
Q

Does LMWH require monitoring?

A

No

But you can using Anti-Xa assay

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14
Q

What is the main side effect of heparin?

A

Bleeding

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15
Q

Heparin can trigger an autoimmune reaction causing which deficiency?

A

Thrombocytopaenia

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16
Q

Name three side effects of heparin.

A

Bleeding

Thrombocytopaenia (autoimmune)

Osteoporosis (long term use)

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17
Q

What happens if you overdose a patient on heparin?

A

Bleeding

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18
Q

Heparin has a (short / long) half life.

A

short half life

so if bleeding or requiring a procedure you can just stop it

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19
Q

In emergencies, which drug can be used to reverse the effects of heparin?

A

Protamine sulphate

20
Q

Which clotting factors does

a) unfractionated
b) LMW

heparin act on?

A

a) Thrombin

b) Xa

21
Q

Which anticoagulant drug inhibits the action of Vitamin K?

A

Warfarin

22
Q

What is the mechanism of action of warfarin?

A

Inhibits action of Vitamin K

REDUCING ACTIVATION FACTORS II, VII, IX AND X

23
Q

Where are clotting factors produced?

A

Liver

24
Q

What is required for the production of factors II, VII, IX and X in the liver?

A

Vitamin K

25
Q

Do patients on warfarin still produce clotting factors?

What is the significance of this?

A

Yes

The clotting factors are non-functional, need to be activated by Vitamin K

Vitamin K can be used to reverse the effects of warfarin

26
Q

Warfarin has a narrow ___ ___.

A

therapeutic index

27
Q

Which family of enzymes metabolises warfarin in the liver?

A

Cytochrome P450

28
Q

Warfarin dosage depends on what?

A

Patient’s INR after first dose of 5 - 10 mg

i.e liver clearance of warfarin by CYP450

29
Q

When should warfarin be taken?

A

Same time every day

30
Q

Which clotting time is used to measure warfarin response?

A

INR

Which is a different way of measuring PT

31
Q

Which clotting factors does warfarin affect?

A

II

VII

IX

X

32
Q

What is INR?

A

International normalised ratio

Standardised method of measuring a prothrombin time

since people were using different reagents to do the test

33
Q

What is the main side effect of warfarin?

A

Bleeding

34
Q

Warfarin ___ with other drugs.

A

interacts

35
Q

Which substance inhibits the liver’s ability to metabolise warfarin?

A

Alcohol

Alcohol intake increases bleeding risk in patients on warfarin

36
Q

What is the half life of warfarin compared to heparin?

What does this mean in the context of bleeding?

A

T1/2 warfarin > T1/2 heparin

Omitting warfarin won’t control bleeding as effectively as heparin omission

37
Q

Apart from stopping warfarin, what can be done to reverse warfarin overdose?

A

Vitamin K PO / IV

Clotting factors (give FFP)

38
Q

Why is warfarin omission and oral Vitamin K attempted before giving warfarin patients clotting factors via FFP?

A

Exposure to BBVs (inc. ones we don’t know about)

39
Q

How long does Vitamin K require to take effect?

A

6 hours

ish

40
Q

How long does FFP require to take effect?

A

Immediate

41
Q

Which clotting factor does rivaroxaban act on?

A

Xa

‘xa’ in the name hints that the drug is a Factor Xa inhibitor

42
Q

Which clotting factor does dabigatran ​act on?

A

Thrombin

43
Q

Which clotting factor do rivaroxaban, apixaban and edoxaban ​act on?

A

Xa

‘xa’ in the name

44
Q

How are NOACs taken?

A

PO

45
Q

What is an

a) advantage

b) disadvantage

of using NOACs versus warfarin?

A

a) Arguably more effective; No monitoring required

b) No antidote

46
Q

Protamine sulphate is used to reverse (heparin / warfarin) overdose.

A

heparin overdose

47
Q

Vitamin K is used to reverse (heparin / warfarin) overdose.

A

warfarin overdose

Haematology Week 2 2018/19 (7 decks)

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