Anti- platelet and anti- coagulants

Question 1

What is the difference in appearance, consequence and method of prevention of arterial vs venous clots?

Answer 1

Appearance: arterial= red// venous= white
Consequence: A–> MI, stroke// V–> DVT, PE
Prevention: A need anti-platelets, V need anti- coagulants

Question 2

What activates the intrinsic and extrinsic pathways??

Answer 2

Intrinsic= exposure of tissue factor in basement membrane- activates factor X
Extrinsic= abnormal surface (class, collagen) leading to factor XII activation

Question 3

What 3 factors lead to increased coagulability? (virchows triad)

Answer 3

• abnormality in vessel wall
• abnormality in flow
• abnormality in blood components

Question 4

How does warfarin work?

Answer 4

inhibits production of vitamin K dependant clotting factors (VII, IX and X)

Question 5

Why do most people need to take heparin as well for the first 3 days of starting warfarin?

Answer 5

Because it takes a few days for the existing clotting factor to be used up and not replaced

Question 6

What effect will alcohol and NSAIDS have on warfarins effect?

Answer 6

Both will increase effect, alcohol because it inhibits the CYP enzyme which metabolised warfarin and NSAIDS because it displaces warfarin from plasma proteins it binds to.

Question 7

Why is warfarin avoided in young women?

Answer 7

It is teratogenic

Question 8

Name 3 things which will inhibit warfarins effect

Answer 8

Leafy greens, cererals, antiepileptics, rifampicin, st johns wort–> these induce CYP450s

Question 9

Give 3 indications of warfarin

Answer 9

AF, DVT, PE, prosthetic heart valve

Question 10

Give 3 side effects of warfarin

Answer 10

bleeding, bruises, severe headache, vomiting, confusion

Question 11

How can warfarin be reversed?

Answer 11

• Stop warfarin (needs 3 days to get back to normal)
• Give vitamin K IV if acutely unwelll
• Consider giving fresh frozen plasma and prothombin complex concentrate if severe bleeding
• Consider surgery to find source of bleeding

Question 12

What are the two types of heparin and whats the difference between them?

Answer 12

Low molecular weight heparin- eg dalteparin, daily sub cut injections
Unfractionated heparin - IV bolus infusion

Question 13

How does heparin work?

Answer 13

Heparins are glycosaminoglycans which bind and activate anti- thrombin III which then deactivates factor Xa. Unfractioned heparin also inhibits IIa by activating anti- thrombin III.

Question 14

Describe the monitoring required of LMWH and unfractioned heparin

Answer 14

LMWH does need monitoring as response is very predictable. Unfractioned isn’t so requires monitoring

Question 15

How fast do heparins work?

Answer 15

Fairly rapidly, also reverse fast on stopping use

Question 16

Briefly describe the initiation of warfarin

Answer 16

Loading dose of 10mg, usually. Dose on second day will depend on INR response, gradually dose lowered until INR is within required range (usually 2-3). Cover first 3 days with heparin.

Question 17

When is heparin used?

Answer 17

• LMWH peri operatively in low doses as youve removed warfarin
• LMWH during first few days of initiating warfarin treatment
• Reduce reoccurance/ extension of coronary artery thrombosis in unstable angina and MI
• Instead of warfarin in pregnancy

Question 18

Give 3 ADRs of heparin

Answer 18

• intracranial bleeds
• bleeding at injection sites
• thrombocytopenia (may trigger autoimmune destruction of platelets)
• osteoporosis with long term use

Question 19

How is heparin reversed?

Answer 19

Using protamine sulphate - dissociates heparin by binding to anti- thrombin III

Question 20

How does dabigatran work?

Answer 20

It is a thrombin (factor IIa) inhibitor

Question 21

List 3 anti-platelet drugs

Answer 21

Aspirin, dipyridamole, clopidogrel

Question 22

How does dipyridamole work? when is it used?

Answer 22

phosphodiesterase inhibitor, this in turn inhibits platelet activation- uses lots in secondary preventions of strokes but can cause flushings and headaches

Question 23

How does clopidogrel work and when is it used?

Answer 23

ADP antagonist, used in acute coronary syndromes and post PCI

Question 24

Name two fibrinolytics other than streptokinase

Answer 24

Alteplase, reteplase

Question 25

How do alteplase and reteplase work?

Answer 25

They are tissue plasminogen activators (tPA), tPA cleaves plasminogen into plasmin, which breaks down fibrin in the clot. It also breaks down fibrinogen systemically (bad), but less so than streptokinase.