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

Block 3 - Anticoagulants Med Chem Flashcards

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?

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?

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?

A

Factor IIa inhibitors because thrombin is factor IIa

22
Q

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

A

Indirect inhibitors; Direct binds to antithrombin → inhibiting thrombin

23
Q

What are the binding sites of direct thrombin inhibitors?

A

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

24
Q

What are the direct thrombin inhibitors?

A
  1. Lepirudin (Refludan)
  2. Desiruden (Iprivask)
  3. Bivalirudin (Angiomax)
  4. Argatroban (Novastan)
  5. Hirudin
25
Q

What is hirudin?

A

Care from medical leeches

26
Q

What are the analogues of hirudin?

A

Lepirudin and desirudin

27
Q

What the mechanism of bivalrudin?

A

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
Q

What are some of the Argotroban properties?

A
  1. 1st small molecule DTI
  2. IV or SC (too hydrophilic → non-oral)
  3. Produces 3 metabolites
29
Q

How does Dabigatran differ from other DTI?

A

1st PO active DTI
Prodrug of one ester, one carbamate

Bis-hydrolysis must happen in order to produce active drug

30
Q

What is the dabigatran reversal agents?

A

Praxbind (Idarucizumab)

31
Q

What is the MOA of idarucizumab?

A

Binds to dabigatran with much higher affinity that dabigatran binds to thrombin

Homanized monoclonal antibody

32
Q

What are the Factor Xa inhibitors?

A
  1. Rivaroxaban (Xarelto)
  2. Apixiban (Eliquis)
  3. Endoxaban (Savaysa)
33
Q

What is the MOA of rivaroxaban?

A

Binds to both free and bound Factor Xa creating a prothrombinase complex

Highly selective factor Xa inhibitor

34
Q

What is the MOA of apixaban?

A

Eliquis is highly selective factor Xa inhibitor creating a prothrombinase complex

35
Q

What are the reversal agents for Factor Xa inhibitors?

A
  1. Andexanet alfa (Andexxa): Recombinant factor Xa (rFXa)
36
Q

What is the MOA of Andexxa?

A

Rivaroxaban/apixiban bind to rFXa with same affinity as endogenous FXa

37
Q

What the Vitamin K antagonists?

A
  1. Warfarin (Coumadin)
38
Q

Describe Warfarin binding?

A

Looks like vitamin K and inhibits Vitamin K 2,3- quinone/epoxide reductase

39
Q

What are the biggest barriers of warfarin?

A
  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
Q

What are the reversal agents of warfarin?

A
  1. Mephyton (phytonadione/Vitamin K1)
  2. Centra (Prothrombin Complex concentrate)
41
Q

What is the purpose for mephyton?

A

Replenishes vitamin K in order to overcome effects providing competition

42
Q

How does Kcentra provide warfarin reversal?

A

Replacement of the coagulation cascade factors deactivating warfarin

43
Q

What are the components of KCentra?

A
  1. Mix of Factors II, VII, IX, X
  2. Contains Protein C and S (prothrombics)
  3. Albumin
44
Q

What are high vitamin K sources?

A

Spinach, cheddar cheese, cabbage

45
Q

What enzymes metabolize Warfarin?

A

CYP2C9, Cyp2C19, CYP1A2

46
Q
A

Drug Action I (32 decks)

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