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CPT > Anticoagulants > Flashcards

Anticoagulants Flashcards

1
Q

What are coagulation factors present in the blood as?

A

Zymogens

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2
Q

What is an endogenous inactivator of clotting factors?

A

Antithrombin III

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3
Q

What is an important cofactor in the coagulation cascade?

A

Calcium

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4
Q

Type of heparin

A
  • Unfractionated heparin
  • Low molecular weight heparins e.g. dalteparin, enoxaparin
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5
Q

Compare the administration of unfractionated heparin + LMWH

A
  • UFH: IV bolus + infusion or s.c. For prophylaxis
  • LMWH: s.c.
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6
Q

What is the mechanism of action of unfractionated heparin?

A
  • Binds to antithrombin III > confirmation change > increases activity of ATIII > Xa inhibiton
  • to catalyse inhibition of thrombin, binding to ATIII and IIa is needed
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7
Q

What is the mechanism of action of LMWH

A
  • inhibition of factor Xa by enhancing ATIII activity
  • no affect on thrombin
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8
Q

Why does LMWH have no affect on thrombin?

A

It is too short so cannot bind to both IIa and ATIII

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9
Q

What is the mechanism of action of fondaparinux?

A

inhibition of factor Xa by enchanting ATIII

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10
Q

Compare the half life of unfractionated heparin + LMWH

A
  • UH: 20 mins low dose, 2hrs high dose
  • LMWH: 2+ hours
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11
Q

Why is heparin not given orally?

A

Large negatively charged molecules > would have very poor GI absorption

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12
Q

Uses of hepatitis + fondaparinux

A
  • prevention of venous thromboembolism - DVT + PE
  • ACS with dual anti platelet therapy
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13
Q

What are adverse drug reactions of heparins?

A
  • bruising + bleeding
  • herparin induced thrombocytopenia (more likely in UFH)
  • osteoporosis
  • hyperkalameia (due to inhibition of aldosterone secretion)
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14
Q

What is heparin induced thrombocytopenia?

A
  • antibodies to heparin platelet factor 4 complex produced
  • depletion of platelets
  • paradoxically can lead to thrombosis as more platelets activated by damaged endothelium
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15
Q

What are important drug drug interactions of heparins?

A

Other antithrombotic drugs
ACEi/ARBs
K+ sparing diuretics

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16
Q

Outline heparins monitoring

A
  • aPTT used to monitor UFH
  • less monitoring for LMWH as more predictable in action
17
Q

Outline the reversal of heparins

A

protamine sulphate
- forms inactive complex with heparin
- heparin dissociates from ATIII
- greater effect with UFH than LMWH + no affect on fondaparinux

18
Q

Example of vitamin K antagonist

A

Warfarin

19
Q

What are the uses of warfarin?

A
  • venous thromboembolism
  • PE
  • DVT + secondary prevention
  • superficial vein thrombosis
  • AF when DOAC not suitable
  • pre cardio version
  • in heart valve replacement
20
Q

What is the mechanism of action of warfarin?

A
  • inhibits activation of vitamin K decent clotting factors II, VII, IX + X
  • inhibits conversion of vitamin K to active reduced form
21
Q

What clotting factors are vitamin K dependent?

A

II
VII
XI
X

22
Q

What is the onset of action + half life of warfarin?

A
  • delayed onset of action
  • t1/2 - 36-48 hours
23
Q

What are contraindication for warfain?

A

Crosses placenta so avoid in pregnancy (especially 1st trimester)

24
Q

What are adverse drug reactions of warfarin

A
  • bleeding
  • epistaxis
  • spontaneous retroperitoneal bleeding
25
Q

Outline the reversal of warfarin

A
  • vitamin K
  • prothrombin complex concentrate IV
  • stop warfarin
26
Q

What does a high and low INR mean?

A

High INR - more anti coagulate
Low INR - less anti coagulated

27
Q

What are important drug drug interactions with warfarin?

A
  • CYP2C9 inhibitor
  • other anticoagulants
  • phenytoin, barbiturates, rifampicin, St John’s warts: increase [plasma]
  • NSAIDs: both bind to albumin
28
Q

Examples of DOACs

A

Apixaban
Edoxaban
Rivaroxaban
Dabigatran

29
Q

What are the uses of DOACs?

A

Indicated in most situations where warfarin used to be the only option

30
Q

What DOACs affect factor Xa and what is their mechanism of action?

A
  • Apixaban, Rivaroxaban, edoxaban
  • inhibtion free Xa and bound to ATIII
  • do not directly effect thrombin
31
Q

What is the mechanism of action of dabigatran?

A

Competitive thrombin inhibition to both circulation and thrombus bound IIa

32
Q

What are adverse drug reactions of DOACs?

A

Bleeding
Skin reactions

33
Q

What are important drug drug interactions of DOACs

A
  • carbamazepine, phenytoin + barbiturates decrease [plasma]
  • Macrolides increase [plasma]
34
Q

What DOACs is most prescribed + why?

A

Apixaban
Better side effect profile

35
Q

What antidotes are available for DOACs

A
  • andexanet alfa - Apixaban + Rivaroxaban
  • idarucizumab: dabigatran
36
Q

When may warfarin be more appropriate than a. DOAC?

A

Patients with prosthetic valves
Higher risk of GI bleeding
Antiphospholipid syndrome

37
Q

What bleeding risk score is used in AF patients?

A

ORBIT score

38
Q

What factor is used in prothrombin time and why?

A

Factor VII
Most sensitive to vitamin K deficiency

39
Q

Which DOAC is a direct thrombin inhibitor?

A

Dabigatran

CPT (28 decks)

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