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Drugs Lists > Anti-coagulants > Flashcards

Anti-coagulants Flashcards

1
Q

What activates the instrinsic pathway?

A

Exposed collagen

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2
Q

What activates the extrinsic pathway?

A

Tissue factor

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3
Q

Summarise the clotting cascade

A
  1. Extrinsic and intrinsic pathway activate factor X->Xa
  2. This activates prothrombin to thrombin
  3. This activates fibrinogen to fibrin and forms a clot
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4
Q

What electrolyte is important in the clotting cascade?

A

Calcium

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5
Q

How is unfractionated heparin given?

A

IV bolus/infusion

SC for prophylaxis as it gives a much lower bioavailiability

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6
Q

What is unfractionated heparin mechanism of action?

A
  1. Binds to ATIII and causes a conformational change, increasing activity of ATIII
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7
Q

How does unfractionated heparin inhibit thrombin?

A

It needs to bind simultaneously to ATIII and IIa

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8
Q

How does unfractionated heparin inhibit factor Xa

A

It only needs to bind to ATIII

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9
Q

Name two LMWH’s

A

Dalteparin, enoxaparin

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10
Q

How is LMWH given?

A

Subcutaneously

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11
Q

How does LMWH work?

A

It bind to ATIII and inhibits factor Xa only

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12
Q

How does fondaparinux work?

A

It is a synthetic polysaccharide which selectively inhibits Xa by binding to ATIII. Given subcutaneously, t1/2 is 18 hours.

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13
Q

Why does UFH need more monitoring?

How do you monitor it?

A

The dose response is non linear with variable bioavailability. It is monitored by looking at aPTT.

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14
Q

Which heparin do you use in renal impairment?

A

UFH

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15
Q

Which heparin do you use if you need fine control?

A

UFH

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16
Q

Which heparin has a longer half life?

A

LMWH

17
Q

What are some ADR’s related to heparin?

A
  1. Bruising and bleeding - intracranial, GI, epistaxis
  2. Heparin induced thrombocytopenia - Antibodies to heparin platelet factor 4 complex. Platelets deplete but can lead to thrombosis as more platelets activated by damaged endothelium.
  3. Hyperkalaemia - Aldosterone inhibited
  4. Osteoporosis
18
Q

What is protamine sulfate?

A

It forms an inactivate complex with heparin, given IV.

It dissociated heparin from ATIII and causes irreversible binding.

19
Q

How does warfarin work?

A

Inhibits activation of vitamin K dependent clotting factors. Hepatic synthesis of 2, 7, 9 ,10

20
Q

Does warfarin work straight away?

A

No - takes a while as circulated active clotting factors have be used up and takes several days.

21
Q

What is the half life of warfarin?

A

36-48hrs

22
Q

Can you give warfarin in pregnancy?

A

No. Avoid in 1st trimester (teratogenic) and 3rd trimester (haemorrhage).

23
Q

What are some ADR’s of warfarin?

A
  1. Bleeding

2. Epistaxis and spontaneous retroperitoneal bleeding

24
Q

What is a good antidote to warfarin?

A

Vitamin K
Prothrombin complex IV
Stop warfarin

25
Q

What is bridging therapy?

A

Giving LMWH when initiating or temporarily stopping warfarin (surgery, sickness)

26
Q

What are the warfarin DDI’s

A
  1. Any drug that interacts with enzyme inducers/inhibitors
    Amidodarone, clopidogrel, high alcohol dose, quinolone, metronidazole,
    - cephalosporins (they reduce gut bacteria that inhibit vit K)
    - NSAID’s - Displace warfarin from plasma albumin. Decreased gut absorption of vit K. Increase INR.
    - ‘CRAPS’ P450 inducers decrease INR.
27
Q

How do you monitor a patient on warfarin?

A

INR

28
Q

What is an ideal INR?

A

<1.1

29
Q

What is a target INR in patients with DVT, PE, AF?

A

INR 2-3

30
Q

What is a target INR in patients with recurrent DVT or PE?

A

3.0 - 3.5

31
Q

Name 3 DOAC’s

A

Apixaban, edoxaban, rivaroxaban

32
Q

How do DOAC’s work?

A

They inhibit free Xa and those bound to ATIII. Hepatic metabolism and slightly kidneys. Half life 10hrs.

33
Q

How does dabigatran work

A

A direct competitive thrombin inhibitor, both circulating and thrombus bound IIa.

34
Q

Do you need to monitor DOAC’s?

A

No

35
Q

How are DOAC’s given?

A

Orally

36
Q

What are some ADR’s of DOAC’s?

A
  1. Bleeding, caution in GI bleed groups
  2. Metabolism by many routes. Don’t use dabigatran in low creatinine clearance.
  3. Affects by CYP inhibitors/inducers. Plasma increased by macrolides.
  4. Lower intracranial bleed risk than warfarin.
37
Q

Can you use DOAC’s in pregnancy?

A

No

38
Q

Is there an antidote for DOAC’s?

A

Yes, andexanet.

39
Q

When is warfarin used over a DOAC?

A

In renal failure, mechanical valves, if you need to measure compliance

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