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Blood > Anticoagulants, Antithrombotics And Thrombolytics > Flashcards

Anticoagulants, Antithrombotics And Thrombolytics Flashcards

1
Q

What does heparin consist of?

A

Sulphanated GAGs of variable length

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2
Q

What drugs are used in vitro to prevent coagulation?

A

Citrate
EDTA
Heparin

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3
Q

What drugs are used in vivo to prevent coagulation?

A

Heparin
Warfarin
Rivaroxuban
Dabigatran

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4
Q

How does heparin function as an anticoagulant?

A

It binds to and enhances the action of endogenous antithrombin III to ihibit clotting factors 2,9,10,11 and 12

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5
Q

Which clotting factor does low molecular weight heparin predominantly inhibit?

A

Factor 10

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6
Q

What are the advantages of using low molecular weight heparin as opposed to unfractured heparin?

A

High bioavailability of subcutaneous route
Lower incidence of HIT
No need to monitor PTIdeal agent during pregnancy

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7
Q

What are the disadvantages of using low molecular weight heparin as opposed to unfractured heparin?

A

Requires dosage adjustment in renal insufficiency
Cannot be used in patients once HIT develops
Only partially reversible
Expensive
Longer half life may prolong the risk of bleeding

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8
Q

Why is heparin not orally active?

A

Its absorption is prevented by high molecular weight and charge

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9
Q

Heparin can cross the placenta and blood brain barrier. T/F?

A

False

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10
Q

What are the side effects of heparin?

A

Allergic reactions
Haemorrhage
Heparin induced thrombocytopenia

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11
Q

How can heparin induced thrombocytopenia be reduced?

A

By the heparin antagonist protamine

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12
Q

How does warfarin function as an anticoagulant?

A

It blocks vitamin K reductase and so blocks carboxylation of the gamma carboxyglutamate residues of the N terminal of factors 2,7,9 and 10

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13
Q

Why does warfarin take 1-3 days to take effect?

A

It takes this time for the existing pool of clotting factor to be replaced by dysfunctional factors

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14
Q

Most of warfarin in the blood is bound to which protein?

A

Albumim

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15
Q

Why should aspirin never be coadministered with warfarin?

A

Aspirin displaces warfarin from binding sites on albumin which increases plasma warfarin levels leading to an increased risk of haemorrhage

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16
Q

Why is warfarin not used in pre-eclampsia?

A

It can cross the placenta and blood brain barrier

17
Q

How are the effects of warfarin reversed?

A

It is transfused with plasma or coagulation factor concentrates

18
Q

What measurement, derived from the patient’s PT, is used to carefully monitor clotting time due to the high incidence of haemorrhage of warfarin? And what is the target range of this measurement?

A

International normalised ratio

Target range 2.0-3.0

19
Q

Why are dabigatran and rivaroxuban useful compared to heparin and warfarin for use as anticoagulants?

A

There is no need to monitor patients

20
Q

What clotting factor does dabigatran inhibit?

A

Thrombin

21
Q

What clotting factor does rivaroxuban directly inhibit?

A

Factor 10

22
Q

How does aspirin work as an anticoagulant?

A

It irreversibly inhibits the COX pathway to inhibit platelet synthesis of thromboxane A2 and endothelium production of prostacyclin. This inhibits platelet activation

23
Q

How does dipridamole function as a antithrombitic?

A

It inhibits cyclic nucleotide phosphodiesterases to increase cAMP and cGMP which increases the action of prostacyclin and nitric oxide to inhibit platelet activation

24
Q

How does epoprtenol work as a qntithrombitic?

A

It is a stabilised prostacyclin so inhibits platelet activation

25
Q

How does clopidogrel work as a antithrombitic?

A

It blocks platelet ADP receptors which prevents GIIb/IIIa receptor exposure to inhibit platelet activation

26
Q

How does abciximab work as a antithrombitic?

A

It is a monoclonal antibody to GPIIb/IIIa and blocks these receptors to prevent platelet activation

27
Q

What is altepase and why is it used?

A

A human recombinant version of tissue plasminogen activator which activates plasminogen bound to fibrin to act as a thrombolytic

28
Q

How does streptokinase work as a thrombolytic?

A

It binds to plasminogen and activates it by inducing conformational change

29
Q

Which thrombolytic is ineffective after a recent streptococcal infection due to being antigenic?

A

Streptokinase

Blood (6 decks)

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