module 9 anticoagulants

Question 1

antithrombin III and heparin

Answer 1

work together to catalyze inactivation of

• thrombin
• Xa
• IXa
• XIa
• XIIa

Question 2

unfractionated heparin effects on thrombin

Answer 2

binds to antithrombin II and thrombin

- inactivates thrombin

Question 3

unfractionated heparin effects on Xa

Answer 3

binds to antithrombin II via pentasaccaride

- sufficient to inactivate Xa

Question 4

LMW heparin effects on thrombin

Answer 4

binds to antithrombin III but not to thrombin

- poorly inactivates thrombin

Question 5

LMW heparin effects on Xa

Answer 5

binds to antithrombin III via pentasaccharide

- sufficient to inactivate Xa

Question 6

selective factor Xa inhibitor effects on factors

Answer 6

no effect on thrombin
binds to antithrombin III via pentasaccharide
- sufficient to inactivate Xa

Question 7

direct thrombin inhibitor effects on factors

Answer 7

no effect on Xa

selectively inactivates thrombin

Question 8

Unfractionated heparin (UFH)

Answer 8

less selective: inactivates thrombin and Xa

parental

Question 9

Uses of UFH, LMWH, Xa inhibitors, and thrombin inhibitors

Answer 9

prophylaxis and or treatment of DVT/PE
- ineffective for existing clots, prevents formation and propagation of thromboembolism
MI
PCI

Question 10

UFH monitoring

Answer 10

aPTT

• tests intrinsic and extrinsic pathways
• inc. heparin -> inc. time for fibrin clot formation -> inc. aPTT

Question 11

LMWH drugs

Answer 11

enoxaparin
dalteparin
tinzaparin

Question 12

LMWH

Answer 12

more selective: Xa inactivation > thrombin

- 3:1

Question 13

LMWH monitoring

Answer 13

larger TI compared to heparin
- monitoring generally unnecessary
- can measure antifactor Xa
Renally eliminated

Question 14

Heparin-induced thrombocytopenia

Answer 14

development of antibodies to heparin bound platelets
- Type 1
- Type 2
higher incidence with UFH vs LMWH

Question 15

HIT type 1

Answer 15

antibody-coated platelets targeted for removal from circulation
50-75% reduction in platelet counted after 5 days
transient and rapidly reversible: stop heparin

Question 16

HIT type 2

Answer 16

targets platelets for destruction

antibodies cause platelet activation and aggregation -> fatal thrombosis

Question 17

Heparin AE

Answer 17

bleeding
- more likely with UFH 
Antidote: protamine 
- chemically antagonized heparin: directly binds and inactivates 
- partially inactivates LMWH

Question 18

selective factor Xa inhibitor drugs

Answer 18

fondaparinux: parenteral

rivaroxaban, apixabin: oral

Question 19

Xa inhibitor AE

Answer 19

bleeding

- no specific reversal agent: prothrombin complex concentrates or recombinant factor VIIa

Question 20

Direct thrombin inhibitor drugs

Answer 20

lepirudin
hirudin
desirudin
bivalirudin
argatroban
dabigatran: oral

Question 21

direct thrombin inhibitor use

Answer 21

HIT
- prevent further reduction of platelet count while preventing thrombosis 
prophylaxis/ tx DVT/PE
MI
PCI

Question 22

direct thrombin inhibitor AE

Answer 22

bleeding

- no specific reversal agent: prothrombin complex concentrates or recombinant factor VIIa

Question 23

Dabigatran

Answer 23

prodrug: active drug binds competitively to active site of thrombin

Question 24

Dabigatran pro and con

Answer 24

Advantage over warfarin: no freq. lab monitoring

disadvantage: no specific reversibility, inc. bleeding, inc. risk MI