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Haematology > Anticoagulants > Flashcards

Anticoagulants Flashcards

1
Q

What are the main types of anticoagulants?

A

Heparin
Warfarin
DOACs

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2
Q

What is the indication of heparin?

A
  1. VTE - prophylaxis and rx

2. ACS

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3
Q

What are the two types of heparin?

A
  1. LMWH

2. Unfractionated heparin.

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4
Q

What are examples of LMWH?

A

Dalteparin
Enoxaparin
Tinzaparin

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5
Q

Give the mechanism of action of heparin

A

inhibit function of thrombin and factor Xa which are key to formation of fibrin clot

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6
Q

How does unfractionated heparin work?

A

Binds antithrombin, increases ability to inhibit thrombin, factor Xa and IXa

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7
Q

How does LMWH work?

A

similar to UFH but preferentially inhibit factor Xa

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8
Q

Why is LMWH generally preferred to UFH?

A
  • response is more predictable
  • lab monitoring not required
  • only needs to be given OD or BD
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9
Q

what are SEs of heparin?

A
  • ↑ bleeding
  • heparin induced thrombocytopenia (mainly UFH)
  • osteoporosis (long term)
  • hyperkalaemia (beware)
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10
Q

What are the CIs of heparin?

A
  1. Bleeding disorders
  2. Platelets <60
  3. Previous HIT
  4. Peptic ulcer
  5. Cerebral haemorrhage
  6. Severe HTN
  7. Neurosurgery
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11
Q

When should LMWH be used at a lower dose and why?

A

renal impairment
may accumulate
(can use UFH instead)

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12
Q

What drug is similar to heparin and what does it act on?

A

fondaparinux

inhibits factor Xa only

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13
Q

What is the indication of fondaparinux?

A

VTE prophylaxis
Rx of unstable angina and NSTEMI/STEMI - ACS
Rx of DVT + PE

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14
Q

How is UFH administered

A

IV

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15
Q

How is LMWH administered?

A

SC

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16
Q

When is UFH more useful?

A
  1. Situations where there is a high risk of bleeding as anticoagulation can be terminated rapidly
  2. Renal failure
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17
Q

What is an antidote for heparin?

A

protamine sulphate

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18
Q

How does warfarin work?

A

Inhibits vitamin K epoxide reductase preventing reactivation of vitamin K and coagulation factor synthesis
Clotting factors II, VII, IX, X (1972) + protein C

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19
Q

What are the indications of warfarin?

A
  1. VTE - prevent clot extension + recurrence
  2. AF
  3. Prevent heart valve replacement complications
20
Q

What is warfarin NOT used for? Why?

A

to prevent arterial thrombosis e.g. MI, thrombotic stroke

This is driven by platelet aggregation so is prevented by anti platelets e.g. aspirin, clopidogrel

21
Q

When is the target INR 2.5-3?

A

VTE
AF
Cardioversion
Antiphospholipid syndrome

22
Q

When is target INR 3.5?

A

recurrent VTE whilst on anticoagulants

23
Q

What is INR?

A

Ratio of prothrombin time for the patient over the normal prothrombin time

24
Q

What factors make warfarin more active?

A

Liver disease
P450 enzyme inhibitors - amiodarone, ciprofloxacin
Cranberry juice

25
Q

What are SEs of warfarin?

A 
Bleeding e.g. with peptic ulcers, minor trauma 
Skin necrosis (rare)
26
Q

What factors increase risk of bleeding in those on warfarin?

A

Those at increased risk of haemorrhage:

  • > 65yrs
  • Prev. bleeding episode
  • Recent ischaemic stroke, HTN etc
  • Regular NSAIDs
  • XS alcohol, falls
  • Recent or imminent surgery, trauma
27
Q

How is warfarin administered?

A

orally

28
Q

What INR indicates increased bleeding risk?

A

increased INR

29
Q

What test measures how well the coagulation factors in the extrinsic pathway work?

A

PT

30
Q

What test measures the clotting factors of the intrinsic and common pathways?

A

PTT

31
Q

What is PT?

A

Prothrombin time

measures number of seconds it takes for a clot to form

32
Q

What is PTT

A

Partial thromboplastin time (aPTT), partial as absence of tissue factor

33
Q

What is INR?

A

calculation that adjusts for changes in the PT reagents and allows for results from different labs to be compared

34
Q

When should target INR be higher?

A

if there is a higher risk of a blood clot

35
Q

What is the management of major bleeding on warfarin?

A
  1. Stop warfarin
  2. Give IV vit K 5mg
  3. Prothrombin complex concentrate
36
Q

What is the management of minor bleeding with an INR >8

A

stop warfarin
IV vit K 1-3mg
Restart warfarin when INR <5

37
Q

What is the management of INR >8 w no bleeding

A

Stop warfarin
Vit K 1-5mg PO
Restart warfarin when INR <5

38
Q

What is the management of INR 5-8 w minor bleeding?

A

same as >8 w minor bleeding

39
Q

What is the management of INR 5-8 w no bleeding?

A

withhold 1 or 2 doses of warfarin

reduce subsequent maintenance dose

40
Q

What things can lower INR (increase risk of clotting)

A

P450 inducers:

  • AEDs
  • barbiturates
  • rifampicin
  • chronic alcohol
  • St Johns Wort
  • Smoking
41
Q

What things can increase INR (increase risk of bleeding)

A

P450 inhibitors: (decrease W metabolism)

  • abx: ciprofloxacin, erythromycin (macrolide)
  • fluconazole
  • isoniazid
  • protease inhibitors
  • omeprazole
42
Q

What are rivaroxaban and apixaban examples of? how do they work?

A

Direct oral anticoagulants (DOAC)

factor Xa inhibitors, in the NAME lol

43
Q

How does dabigatran work? what is it an example of?

A

DOAC

direct thrombin inhibitor

44
Q

What is the administration route of DOAC?

A

oral

45
Q

What are DOACs used for?

A

Alternative to warfarin

  1. prevention of VTE following hip/knee surgery
  2. Rx of DVT/PE
  3. prevention of stroke in non-valvular AF
46
Q

How should warfarin be given initially?

A

5-10mg given at 18:00 on days 1 and 2
Check INR on day 3
Adjust subsequent doses according to INR

Haematology (18 decks)

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