Anticoagulants, antifibrinolytic and antiplatelet drugs

Question 1

What are the stages of haemostasis?

Answer 1

Constriction of damaged vessels
Mechanical blockage of hole by platelet plug
Coagulation cascade
Thrombolysis

Question 2

What causes platelet activation and aggregation?

Answer 2

Thromboxane A2 (TXA2)
ADP
Thromboxane

Question 3

what is the purpose of fibrinogen?

Answer 3

Links adjacent platelets

Question 4

Other than TXA2, what activates platelets?

Answer 4

Thrombin

Question 5

When does thrombolysis occur?

Answer 5

Fibrin mesh is prevented from increasing so is slowly dissolved by plasmin

Question 6

What 3 stages can drugs target?

Answer 6

Platelets - anti-platelet
Coagulation - anti-coagulant
Thrombolysis - thrombolytic therpay

Question 7

What is the most common anti-platelet drug?

Answer 7

Aspirin

Question 8

Indications for antiplatelet therapy?

Answer 8

Previous MI
Previous stroke
stable angina
Claudication
Atrial fibrillation

Question 9

what kind of anti-platelet drug is aspirin?

Answer 9

Cyclooxygenase inhibitor

Question 10

Function of cyclooxygenase?

Answer 10

Formation of thromboxane

Question 11

Mechanism of action of cyclooxygenase inhibitors like aspirin?

Answer 11

Inhibit the formation of thromboxane - stop platelet activation and aggregation

Question 12

What dose is aspirin given prophylactically?

Answer 12

75mg/day

Question 13

What dose is aspirin given in emergency?

Answer 13

300mg/day

Question 14

Contraindications of aspirin?

Answer 14

Allergies
Age less than 12
GI bleeding
Bleeding disorder
Severe liver disease

Question 15

How do ADP receptor antagonists work?

Answer 15

Inhibit binding of ADP so platelet aggregation cannot occur

Question 16

When are ADP receptor antagonists (clopidogrel) chosen over aspirin?

Answer 16

Safer in GI bleeding

Less toxicity

Question 17

What drugs can clopidogrel (ADP receptor antagonist)?

Answer 17

Proton pump inhibitors

Question 18

When are adenosine re-uptake inhibitors used? (dipyridamole)

Answer 18

Prosthetic heart valves, alternative or in addition to aspirin

Question 19

When is dipyridamole (adenosine re-uptake inhibitor) contraindicated?

Answer 19

Uncontrolled angina - may exacerbate

Question 20

Mechanism of action of anticoagualnt like heparin?

Answer 20

Vitamin K antagonist
Enhance antithrombin III
Inactive prothrombin
Impair platelet function

Question 21

Why can heparin not be given through GI tract?

Answer 21

Poorly absorbed

Question 22

How is heparin adminsitered?

Answer 22

Low dose = subcutaneous

High dose = Iv

Question 23

Why are low molecular weight heparin sometimes used?

Answer 23

Once daily dosing
No need to monitor
Smaller bleeding risk
Reduced risk of thrombocytopeaenia

Question 24

What are the disadvantages of low molecular weight heparins?

Answer 24

Less reversible than heparin

Question 25

Unwanted effects of heparin?

Answer 25

Haemorrhage Thrombocytopenia Allergy

Question 26

What kind of drug is warfarin?

Answer 26

Anti-coagulant - vit K antagonist

Question 27

Why is warfarin slow acting?

Answer 27

Highly protein bound

Question 28

How can warfarin be reversed?

Answer 28

Vit K

Question 29

Disadvantages of warafarin?

Answer 29

Drug interactions with everything

Question 30

Warfarin uses?

Answer 30

Prevent DVT (deep vein thrombosis) Treatment of PE (pulmonary embolism) Atrial fibrillation - prevent risk of embolisation Prosthetic heart valves to prevent emboli developing on valves

Question 31

Problems with warfarin?

Answer 31

Increased risk of bleeding (unless INR is less than 4)

Question 32

How do thrombolytics work?

Answer 32

Plasminogen activators (degrades clots)

Question 33

What is an indication for thrombolysis

Answer 33

Arterial thrombosis

Question 34

When is INR value required?

Answer 34

``` For procedures where there is a risk of bleeding extractions Surgery that involves making a flap extensive RSI IDB ```

Question 35

What is the threshold INR value for no risk of bleeding?

Answer 35

4

Question 36

How does dabigatran work?

Answer 36

Direct thrombin inhibtor

Question 37

Disadvantage of direct oral anticoagulants?

Answer 37

No INR value - dont know how bleeding will go