Antiplatelets, Anticoagulants & Fibrinolytic Agents

Question 1

A is an antiplatelet which works by B inhibiting C in platelets which is needed for production of Thromboxane A2.

Answer 1

A: Aspirin
B: irreversibly
C: COX-1

Question 2

A & B are antiplatelets which work by increasing levels of cAMP.

Answer 2

A: Dipyridamole
B: Clopidogrel

Question 3

Describe the mechanism of action of clopidogrel.

Answer 3

1. Clopidogrel is a non-competitive inhibitor of P2Y12 Gi-protein-coupled receptor
2. It increases conversion of ATP to cAMP via action of adenylate cyclase
3. This decreases levels of Ca2+
4. Activation & aggregation of platelets are inhibited

Question 4

Describe the mechanism of action of dipyridamole

Answer 4

1. Dipyridamole increases levels of cAMP by inhibiting phosphodiesterase which converts cAMP to adenosine monophosphate
2. Increase in cAMP decreases Ca2+
3. Activation & aggregation of platelets are inhibited

Question 5

___ is an antiplatelet which works by inhibiting glycoproteins IIb & IIIa. Fibrinogen link activated platelets together via glycoproteins IIb & IIIa.

Answer 5

Abciximab

Question 6

___ is an antiplatelet which works by inhibiting glycoproteins IIb & IIIa. Fibrinogen aggregate activated platelets via glycoproteins IIb & IIIa.

Answer 6

Abciximab

Question 7

Why is Abciximab administered intravenously?

Answer 7

It’s a protein. Hence, oral administration will result in digestion.

Question 8

Activates plasminogen (apart from tPA) indirectly

Answer 8

Streptokinase

Question 9

Apart from indirectly activating plasminogen, streptokinase also inhibits A, B & C.

Answer 9

A: fibrinogen
B: factor V
C: factor VII

Question 10

Converts clot-specific plasminogen into plasmin

Answer 10

Altepase

Question 11

Anticoagulants

Answer 11

Heparin

Question 12

What do intact endothelium, protein C, antithrombin & prostacyclin have in common?

Answer 12

They inhibit coagulation cascade/are anticoagulants.

Question 13

LMWHeparin

Answer 13

Enoxaparin

Question 14

Which factor do enoxaparin & fondaparinux inhibit?

Answer 14

Xa

Question 15

Heparin inhibits A & B.

Answer 15

A: factor Xa
B: thrombin

Question 16

When (LMW)heparin attaches itself to antithrombin, antithrombin undergoes a change in ___.

Answer 16

shape

Question 17

Synthetic pentasaccharide

Answer 17

Fondaparinux

Question 18

Refer to slide 28 for additional info on UFH, LMWH & Fondaparinux

Answer 18

Slide 28

Question 19

Advantages of prescribing LMWH/enoxaparin & fondaparinux over heparin

Answer 19

1. Can be prescribed on an outpatient basis
2. Don’t require monitoring of activated partial thromboplastin time (aPTT)
3. Less bleeding tendencies
4. Half-lives aren’t dose-dependent

Question 20

Antidote for heparin

Answer 20

Protamine sulphate

Question 21

Pathophysiology of heparin-induced thrombocytopenia (low platelet count)

Answer 21

Heparin & platelet factor 4 (PF4) form a complex –> production of IgG antibodies against heparin-PF4 complex –> IgG antibody-heparin-PF4 immunocomplex binds on platelet surface –> platelet activation & aggregation –> consumption of platelets (thrombocytopnenia) & thrombosis

Question 22

Irreversible direct thrombin inhibitor

Answer 22

Lepuridin

Question 23

Warfarin inhibits hepatic A, thereby blocking synthesis (recycling) of active, B form of vitamin K. Without reduced vitamin K, C of D residues can’t occur, which reduces production of active coagulation factors E, F, G & H, as well as I proteins C & S.

Answer 23

A: epoxide reductase
B: reduced
C: y-carboxylation 
D: glutamate
E: II (2)
F: VII (7) 
G: IX (9)
H: X (10)
I: anticoagulatory

Question 24

Used to treat heparin-induced thrombocytopenia

Answer 24

Lepuridin

Question 25

Non-vitamin K oral anticoagulants (NOAC)

Answer 25

Reversible direct thrombin inhibitor: dabigatran | Reversible direct factor "Xa" inhibitor: rivaro"Xa"ban

Question 26

Lepuridin is administered intravenously. T/F?

Answer 26

True

Question 27

aPTT of patients taking lepuridin don't need to be monitored. T/F?

Answer 27

False

Question 28

Heparin is administered ___.

Answer 28

intravenously

Question 29

LMWH & fondaparinux are administered ___.

Answer 29

subcutaneously

Question 30

Treatment with warfarin is monitored by measuring ___.

Answer 30

Prothrombin time

Question 31

Antidote for warfarin

Answer 31

Vitamin K

Question 32

Warfarin should NOT be prescribed to ___.

Answer 32

pregnant women

Question 33

How do rifampicin & phenytoin affect warfarin?

Answer 33

Rifampicin & phenytoin induces breakdown of warfarin via induction of cytochrome P450

Question 34

How do sulfonamides affect warfarin?

Answer 34

Sulfonamides competitively displace warfarin from plasma protein binding sites

Question 35

How do erythromycin, grapefruit juice & ketoconazole affect warfarin?

Answer 35

Erythromycin, grapefruit juice & ketoconazole increase levels of warfarin by inhibiting cytochrome P450

Question 36

Anticoagulant of choice during pregnancy

Answer 36

Heparin