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Year 3 - Haematology > Anticoagulant Drugs > Flashcards

Anticoagulant Drugs Flashcards

1
Q

What are indications for anticoagulant drugs?

A

Venous thrombosis
Atrial fibrillation

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2
Q

Anticoagulant drugs large what?

A

The formation of fibrin clot

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3
Q

Describe why venous thrombosis can happen

A

Venous system is a low pressure system
Platelets not activated
Activates coagulation cascade - rich in fibrin clot

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4
Q

What is the mechanism of action of heparin

A

Potentiates antithrombin

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5
Q

How quick to act is heparin?

A

Immediate effect

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6
Q

What are the two ways to deliver heparin?

A

IV or SC

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7
Q

What 2 forms of heparin exist?

A

Unfractionated
Low molecular weight (LMWH)

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8
Q

Describe what parts of the pathway unfractionated and LMWH affect

A
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9
Q

How do we monitor heparin?

A

Activated partial thromboplastin time (APTT) for unfractionated

Anti-Xa assay for LMWH but usually no monitoring of LMWH is required as more predictable response

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10
Q

What are complications of heparin?

A

Bleeding
Heparin induced thrombocytopenia (with thrombosis) HITT - monitor FBC in patients on heparin
Osteoporosis with long term use

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11
Q

How do we reverse heparin?

A

Stop the heparin (short t1/2)

Occasionally in severe bleeding
- Protamine sulphate which reverse antithrombin effect (complete reversal for unfractionated; partial reversal for LMWH)

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12
Q

What is the mechanism of action of coumarin anticoagulants?

A

Inhibition of vitamin K

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13
Q

What are examples of coumarin anticoagulants?

A

Warfarin
Phenindione
Acenocoumarin
Phenprocoumon

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14
Q

Where is vitamin K absorbed and what does it require for absorption?

A

Fat soluble vitamin - requires bile salts for absorption

Absorbed in upper intestine

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15
Q

Vitamin K is required for what clotting factors?

A

Final carboxylation of clotting factors II, VII, IX and X

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16
Q

What are the vitamin K dependent factors?

A

Factors II (prothrombin), VII, IX and X; protein C and protein S

17
Q

Where are vitamin K dependent factors synthesised?

A

In liver

18
Q

How does vitamin K work?

A

Carboxylation of glutamic acid residues in factors II, VII, IX, X (as well as protein C and S)

19
Q

How does warfarin work?

A

Blocks ability of vitamin K to carboxylate the vitamin K dependent clotting factors, thereby reducing their coagulant activity

20
Q

What is the INR equation?

A
21
Q

What is INR (international normalised ratio)?

A

A mathematical correction that normalises the PT ratio by adjusting for variability in the sensitivity of different thromboplastin

Allows for comparison of results between labs and standardises reporting of prothrombin time

22
Q

What is the major adverse effect of warfarin?

A

Haemorrhage

23
Q

What mild and severe bleeding complications can occur secondary to warfarin treatment?

A

Mild - skin bruising, epistaxis, haematuria

Severe- GI, intracerebral, significant drop in Hb

24
Q

How do you reverse warfarin?

A
25
Q

How do we manage bleeding as a result of warfarin?

A

Dependent on severity of bleeding and INR

Speed of action
- Vitamin K (6 hours)
- Clotting factors (immediate)

26
Q

What do new anticoagulants like oral Xa inhibitors and oral direct thrombin inhibitors do?

A
27
Q

What does warfarin target?

A
28
Q

What do thrombin inhibitors e.g. dabigatran do ?

A
29
Q

What do Xa inhibitors like edoxaban, rivaroxaban and apixaban do?

A
30
Q

What are examples of new anticoagulants?

A

Direct thrombin inhibitors (dabigatran)
Direct activated factor X inhibitors (edoxaban, rivaroxaban, apixaban)

31
Q

Why are new anticoagulants useful?

A

Less drug interactions
Oral and no monitoring required

32
Q

New anticoagulants can be used for what?

A

Treatment of DVT / PE

Year 3 - Haematology (35 decks)

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