Anticoagulant drugs Flashcards

1
Q

Features of venous thrombosis?

A

Low pressure system
Platelets not activated
Activates coagulation cascade, rich in fibrin clot

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2
Q

What effect does anti thrombin have on the coagulation cascade?

A

Inhibits Thrombin

Inhibits factors VIIa, Xa, IXa and XIa

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3
Q

Mode of action of heparin>

A

Potentiates antithrombin causing anticoagulation

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4
Q

Features of heparin?

A

Immediate effect

IV or S/C

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5
Q

Differences between unfractionated heparin and LMWH?

A

LMWH have greater inability to inactivate factor Xa and less effect on thrombin and platelet function–> less tendency to cause bleeding

No monitoring needed for LMWH as less interactions (anti Xa assay in rare circumstances)

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6
Q

How can unfractionated heparin be monitored

A

APTT

Activated partial thromboplastin time

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7
Q

Complications of heparin?

A

Bleeding
Heparin induced thrombocytopenia (monitor FBC)
Osteoporosis with long term use (due to effect on osteoclast activity)

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8
Q

Heparin reversal?

A

Stop heparin

Occasionally in severe bleeding:
- Protamine sulphate which reverses antithrombin effect

Partial reversal for LMWH
Full for unfractionated

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9
Q

What effect does vitamin K have on clotting factors?

A

II, VII, IX and X

Causes final carboxylation of these (adding COOH group)

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10
Q

Mechanism of action of warfarin?

A

Inhibition of vit K

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11
Q

Why are patients more likely to clot acutely when starting warfarin for the first 2/3 days?

A

Protein C and S (natural anticoagulants) are affected first in warfarin treatment, need to give heparin for 1st week

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12
Q

If second COOH group is not present on the clotting factor what is the consequence?

A

Chemical bond is too weak for effective attachment of coag factor to platelet –>Failure of cascade

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13
Q

How is warfarin metabolised?

A

Enzyme CYP450

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14
Q

How is INR calculated?

A

Patients PT/ Mean normal PT

to power of international sensitivity index

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15
Q

Adverse effects of Warfarin?

A

Haemorrhage

Drug interactions

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16
Q

Reversing Warfarin overdose?

A

Vit K- takes 6 hours

Clotting factors- Immediate

17
Q

Mode of action of Dabigatran?

A

Thrombin inhibitor

18
Q

Mode of action of Rivaroxabam and Apixaban?

A

Factor Xa inhibitors