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Drug Action I > Block 3 - Anticoagulants Med Chem > Flashcards

Block 3 - Anticoagulants Med Chem Flashcards

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1
Q

What are the types of anticoagulants?

A
  1. Heparins
  2. Direct thrombin inhibitors
  3. Direct factor Xa inhibitors
  4. Warfarin
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2
Q

What drugs facilitate clotting?

A
  1. Replacement factors
  2. Vitamin K
  3. Antiplasmin drugs
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3
Q

What is the difference between intrinsic and extrinsic?

A

Intrinsic: internal damage
Extrinsic: Trauma

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4
Q

What factors are inhibited by heparin?

A

XIIa, XIa, IXa, Xa, IIa, XIIIa

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5
Q

What factors are inhibited by warfarin?

A

IX, X, VII, II

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6
Q

At what point do the intrinsic and extrinsic pathway converge?

A

Xa

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7
Q

Describe the process of fibrin crosslinking?

A

Glutamine and lysine comes together by factor XIIIa → cross linked fibrin

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8
Q

Describe the structure of heparin based anticoags.? How does it affect its dosage form?

A

Polymeric in nature → require IV administration to by pass first pass

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9
Q

What is the brand name for UFH?

A

Calcilean

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10
Q

What is the MOA of heparin?

A

Binds to antithrombin III (endogenous) using a pentasaccharide sequence

Heparin increased the binding rate between antithrombin and coagulation factor → inactivating it

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11
Q

What is the difference between unfractioned and LMW heparin binding?

A
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12
Q

What is the MOA of UFH?

A

Binds to many proteins including platelet factor 4 → HIT

High affinity fro antithrombin III → inhibition of thrombin and factor Xa

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13
Q

How is UFH dosed? Monitored?

A

Dose: Standard is 120USP/mg
Monitoring: aPTT (activated partial thromboplastin time) for intrinsic; INR for extrinsic

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14
Q

What is 1 USP?

A

Quantity required to prevent 1 mL of sheep blood from clotting for 1 hr

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15
Q

What is the MOA of LMWH?

A

Same as UFH however is more selective for Xa and has less HIT

More reliable

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16
Q

How is LMWH monitored?

A

Does not require it → reliable dosing and metabolism

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17
Q

How does fondaparinux differ from the other heparin drugs?

A

More specific for Xa than LMWH (no thrombin inhibition)

100% bioavailability, no metabolism, no plasma protein binding due to its synthetic nature

Very hydrophilic

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18
Q

What are the reversal agents of heparin? What is the fastest?

A
  1. Recombinant factor VIIa
  2. Protamine sulfate
  3. Platelet transfusion the fastest in emergency situations
  4. Fondaparinux
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19
Q

How does recombinant factor VIIa reverse heparin?

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A

More VIIa means more Factor X converted to Xa → Increasing crosslinking fibrin and coagulation

20
Q

How does protamine sulfate reverse heparin? What are the disadvantages?

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A

Protamine is a basic (arginine) protein that binds to carboxylate on heparin → ionic binding that forms a stable and inactive complex

Lots of ADRs

21
Q

What is another name for direct thrombin inhibitors?

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A

Factor IIa inhibitors because thrombin is factor IIa

22
Q

All thrombin inhibitors from heparin are classified as ____? How do direct differ?

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A

Indirect inhibitors; Direct binds to antithrombin → inhibiting thrombin

23
Q

What are the binding sites of direct thrombin inhibitors?

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A

Active site (catalytic) and exosite 1 (responsible for binding fibrin)

24
Q

What are the direct thrombin inhibitors?

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A
  1. Lepirudin (Refludan)
  2. Desiruden (Iprivask)
  3. Bivalirudin (Angiomax)
  4. Argatroban (Novastan)
  5. Hirudin
25
What is hirudin?
Care from medical leeches
26
What are the analogues of hirudin?
Lepirudin and desirudin
27
What the mechanism of bivalrudin?
Binds to both the active and execute of thrombin, action is reversible from metabolism Short DOA and quick onset Doesn't elicit antibody formation
28
What are some of the Argotroban properties?
1. 1st small molecule DTI 2. IV or SC (too hydrophilic → non-oral) 3. Produces 3 metabolites
29
How does Dabigatran differ from other DTI?
1st PO active DTI Prodrug of one ester, one carbamate Bis-hydrolysis must happen in order to produce active drug
30
What is the dabigatran reversal agents?
Praxbind (Idarucizumab)
31
What is the MOA of idarucizumab?
Binds to dabigatran with much higher affinity that dabigatran binds to thrombin Homanized monoclonal antibody
32
What are the Factor Xa inhibitors?
1. Rivaroxaban (Xarelto) 2. Apixiban (Eliquis) 3. Endoxaban (Savaysa)
33
What is the MOA of rivaroxaban?
Binds to both free and bound Factor Xa creating a prothrombinase complex Highly selective factor Xa inhibitor
34
What is the MOA of apixaban?
Eliquis is highly selective factor Xa inhibitor creating a prothrombinase complex
35
What are the reversal agents for Factor Xa inhibitors?
1. Andexanet alfa (Andexxa): Recombinant factor Xa (rFXa)
36
What is the MOA of Andexxa?
Rivaroxaban/apixiban bind to rFXa with same affinity as endogenous FXa
37
What the Vitamin K antagonists?
1. Warfarin (Coumadin)
38
Describe Warfarin binding?
Looks like vitamin K and inhibits Vitamin K 2,3- quinone/epoxide reductase
39
What are the biggest barriers of warfarin?
1. Narrow therapeutic index 2. Overdose → inhibition of coagulation → Internal bleeding 3. Must be monitored by a clinical facility → expensive 4. High plasma protein bound can increase or decrease concentration
40
What are the reversal agents of warfarin?
1. Mephyton (phytonadione/Vitamin K1) 2. Centra (Prothrombin Complex concentrate)
41
What is the purpose for mephyton?
Replenishes vitamin K in order to overcome effects providing competition
42
How does Kcentra provide warfarin reversal?
Replacement of the coagulation cascade factors deactivating warfarin
43
What are the components of KCentra?
1. Mix of Factors II, VII, IX, X 2. Contains Protein C and S (prothrombics) 3. Albumin
44
What are high vitamin K sources?
Spinach, cheddar cheese, cabbage
45
What enzymes metabolize Warfarin?
CYP2C9, Cyp2C19, CYP1A2
46

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