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Pharmacology > 21) Anti-Coagulants > Flashcards

21) Anti-Coagulants Flashcards

1
Q

Activated partial thromboplastin time (aPTT) test

A
  • Laboratory test used to monitor the anticoagulant effect of unfractionated heparin and directthrombininhibitors
  • Prolonged when drug effect is adequate
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2
Q

Antithrombin III

A
  • An endogenous anticlotting protein that irreversibly inactivatesthrombinand factor Xa
  • Its enzymatic action is markedly accelerated by the heparins
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3
Q

Clotting cascade

A
  • System of serine proteases and substrates in the blood

- Provides rapid generation of clotting factors resulting in a fibrin clot in response to blood vessel damage

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4
Q

Glycoprotein IIb/IIIa (GPIIb/IIIa)

A
  • A protein complex on the surface of platelets
  • When activated, it aggregates platelets primarily by binding to fibrin
  • Endogenous factors including thromboxane A2, ADP, and serotonin initiate a signaling cascade that activates GPIIb/IIIa
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5
Q

Heparin-induced thrombocytopenia (HIT)

A
  • A hypercoagulable state plus thrombocytopenia that occurs in a small number of individuals treated with unfractionated heparin
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6
Q

LMW heparins

A
  • Fractionated preparations of heparin of molecular weight 2000–6000
  • Unfractionated heparin has a molecular weight range of 15,000–30,000
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7
Q

Prothrombin time (PT) test

A
  • Laboratory test used to monitor the anticoagulant effect ofwarfarin
  • Prolonged when drug effect is adequate
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8
Q

Thrombus vs. embolus

A
  • Thrombus = clot that adheres to a vessel’s wall
  • Embolus = intravascular clot that floats in the blood
  • Detached thrombus becomes an embolus
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9
Q

Arterial thrombosis

A
  • Usually consists of a platelet-rich clot
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10
Q

Venous thrombosis

A
  • Involves a clot that is rich in fibrin

- Fewer platelets than are observed with arterial clots

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11
Q

Platelet aggregation involves the release of platelet granules containing chemical mediators such as

A
  • Adenosine diphosphate (ADP)
  • Thromboxane A2 (TXA2)
  • Serotonin
  • Platelet activation factor (PAF)
  • Thrombin
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12
Q

Two main actions/types of drugs used in clotting disorders

A
  • Drugs used to decrease clotting or dissolve clots already present in patients at risk for vascular occlusion
  • Drugs used to increase clotting in patients with clotting deficiencies
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13
Q

Anticoagulants MOA

A
  • Inhibit the formation of fibrin clots
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14
Q

Three major types of anticoagulants are available

A
  • Heparin and related products (must be used parenterally)
  • Direct thrombin and factor X inhibitors (used parenterally and orally)
  • Orally active coumarin derivatives (eg, warfarin vitamin K antagonists)
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15
Q

Unfractionated heparin (UH)

A
  • Indirect thrombin (IIa) inhibitor
  • Binds to endogenousantithrombin III(ATIII) via a key pentasaccharide sequence
  • Provides anticoagulation immediately after administration
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16
Q

The heparin–ATIII complex

A
  • Combines with and irreversibly inactivates thrombin(IIa) and (Xa)
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17
Q

The action of heparin is monitored with

A
  • Activated partial thromboplastin time(aPTT) laboratory test
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18
Q

LMW heparins that also bind AT-III

A
  • LMWH heparins (Enoxaparin, Dalteparin, Tinzaparin)

- Fondaparinux

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19
Q

Short-chain heparin–ATIII and fondaparinux–ATIII complexes provide

A
  • More selective action because they fail to affectthrombin (II)
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20
Q

The aPTT test does not reliably measure

A
  • Anticoagulant effect of the LMWH and fondaparinux
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21
Q

UH MOA

A
  • Forms UH-ATIII complex

- Irreversibly inactivates factors II and Xa

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22
Q

UH side effects

A
  • Bleeding (monitor with aPTT, protamine is reversal agent)
  • Hemorrhagic stroke
  • Heparin-induced Thrombocytopenia (HIT)
  • Osteoporosis with chronic use
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23
Q

UH characteristics

A
  • Protamine reversal of UH

- OOA = 20-30 min

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24
Q

LMWH: Enoxaparin (lovenox) and dalteparin (Fragmin) MOA

A
  • Forms UH-ATIII complex

- Irreversibly inactivates factor Xa (i.e more selective anti-factor X activity)

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25
Q

LMWH side effects

A
  • Less risk of HIT

- US Box warning: epidural hematoma

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26
Q

LMWH characteristics

A
  • More reliable pharmacokinetics with renal elimination

- Protamine reversal only partially effective

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27
Q

LMWH DOA and OOA

A
  • OOA = 1-2 h

- MOA = 12 h

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28
Q

Fondaparinux (Arixtra)

A
  • Not considered fully a heparin

- Has common moiety with heparin

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29
Q

Fondaparinux (Arixtra) MOA

A
  • Selectively binds to antithrombin III

- Poteniates the neutralization of activated factor Xa

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30
Q

Fondaparinux (Arixtra) side effects

A
  • Anemia

- Very low association with HIT

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31
Q

Fondaparinux (Arixtra) characteristics

A
  • Protamine does not affect fondaparinux

- OOA = 2-3 h

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32
Q

Direct thrombin inhibitors generic/brand names

A
  • Bivalirudin (Angiomax)
  • Argatroban
  • Dabigatran (Pradaxa)
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33
Q

Bivalirudin (Angiomax) MOA

A
  • Binds to thrombin active site and thrombin substrate
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34
Q

Bivalirudin (Angiomax) Pk

A
  • Immediate onset

- DOA = 1-2 h

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35
Q

Bivalirudin (Angiomax), Argatroban, and Dabigatran (Pradaxa) side effects (ALL)

A
  • Bleeding (monitor aPTT)
  • Chest pain
  • Hypotension
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36
Q

Argatroban MOA

A
  • Solely binds to thrombin
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37
Q

Argatroban Pk

A
  • Immediate onset

- DOA = 1-2 h

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38
Q

Dabigatran (Pradaxa) MOA

A
  • Binds to thrombin active site and thrombin substrate
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39
Q

Dabigatran (Pradaxa) Pk

A
  • Only PO
40
Q

Dabigatran (Pradaxa) characteristics

A
  • Idaricizumab binds to dabigatran and reverse its effect
  • US. Box warning: Premature discontinuation of dabigatran
    Increases the risk of thrombotic events
41
Q

Direct Xa inhibitors generic/brand names

A
  • Rivaroxaban (Xarelto)
  • Apixaban (Eliquis)
  • Edoxaban (Savaysa)
42
Q

Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all have the same MOA

A
  • Binds to Xa active site
43
Q

Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all have the same Pk

A
  • Substrate of CYP450
  • Fixed dose PO: no monitoring required
  • Peak = 2-4 h
44
Q

Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all characteristics

A
  • US. Box warning: epidural hematoma
45
Q

Coumarin anticoagulants generic/brand names

A
  • Warfarin (Coumadin)
46
Q

Coumarin anticoagulants action

A
  • Inhibit post-translational modification (that’s why slow onset of action) vitamin-K dependent clotting factors: IIa, VIIa, IXa, Xa
  • Also inhibits the anticlotting factors protein C, protein S
47
Q

The action of warfarin can be reversed with

A
  • Vitamin K

- Recovery requires the synthesis of new normal clotting factors and is slow (6–24 h)

48
Q

Warfarin side effects

A
  • Bleeding (US Box warning)

- Early on period of hypercoagulability with subsequent dermal vascular necrosis can occur (due inhibition of protein C)

49
Q

Warfarin characteristics

A
  • Narrow therapeutic window
  • Substrate of CYP2C9 (patients with genetic variability have dose algorithms)
  • Renally excreted
50
Q

Warfarin has a delayed onset and offset of anticoagulant activity

A
  • OOA: 1-3 days

- DOA: 2-5 days

51
Q

Heparin vs. warfarin structure

A
  • Heparin = large polysaccharide

- Warfarin = small lipid soluble

52
Q

Heparin vs. warfarin route

A
  • Heparin = parenteral

- Warfarin = oral (PO)

53
Q

Heparin vs. warfarin site of action

A
  • Heparin = blood

- Warfarin = liver

54
Q

Heparin vs. warfarin onset

A
  • Heparin = rapid (minutes)

- Warfarin = slow (days)

55
Q

Heparin vs. warfarin MOA

A
  • Heparin = Activate antithrombin III, which inactivates coagulation factors including thrombin and factor Xa
  • Warfarin = Impairs post-translational modification of clotting factors II, VII, IX, X and anticlotting factor (protein C and S) by specifically inhibiting vitamin K epoxide reductase
56
Q

Heparin vs. warfarin monitoring

A
  • Heparin = aPTT for unfractionated heparin but not LMW heparins
  • Warfarin = prothrombin time (PT)
57
Q

Heparin vs. warfarin antidote

A
  • Heparin = Protamine (UH)

- Warfarin = Vitamin K

58
Q

Heparin vs. warfarin use

A
  • Heparin = acute

- Warfarin = chronic

59
Q

Heparin vs. warfarin use in pregnancy

A
  • Heparin = yes

- Warfarin = no

60
Q

Plasmin

A
  • Fibrinolytic enzyme

- Degrades clots by splitting fibrin and fibrinogen in fragments

61
Q

Thrombolytic enzymes

A
  • Catalyze the conversion of the inactive precursor, plasminogen, to plasmin
62
Q

t-PA enzyme

A
  • Directly converts plasminogen to plasmin
63
Q

Tissue plasminogen activators generic/brand names

A
  • Alteplase (Activase)
  • Reteplase (Retavase)
  • Tenecteplase (TNKase)
64
Q

Alteplase (Activase) DOA

A
  • 1 h
65
Q

Reteplase (Retavase) OOA/DOA

A
  • OAA = 30-90 minutes
  • DOA = ?
  • Faster onset and longer DOA than others
66
Q

Tenecteplase (TNKase) DOA

A
  • Longer DOA than others
67
Q

Alteplase (Activase), Reteplase (Retavase), Tenecteplase (TNKase) side effects (ALL)

A
  • Bleeding

- Cerebral hemmhorrage

68
Q

Streprokinase can induce severe allergic reactions

A
  • It can produce antibodies

- Patients who had streptococcal infections may have antibodies to streprokinase

69
Q

Urokinase is human derived

A
  • No allergy problem, but more expensive
70
Q

Protein synthesized by streptococci

A
  • Streptokinase

- Does not show selectivity for fibrin-bound plasminogen.

71
Q

Thrombus is formed on a damaged vascular wall. Platelets are triggered by a variety of endogenous mediators:

A
  • Glycoprotein (GP) Ia receptor (binds to collagen)
  • Glycoprotein (GP) Ib receptor (binds to von Willebrand factor)
  • GP IIb/IIIa (binds fibrinogen)
72
Q

ADP, TXA2 and serotonin

A
  • Aggregating substances that degranulate platelets
73
Q

Substances that increase intracellular cyclic adenosine monophosphate

A
  • Prostaglandin prostacyclin
  • Adenosine
  • They inhibit platelet aggregation
74
Q

Antiplatelet drug classes

A
  • COX inhibitors
  • GP2b/3a inhibitors
  • ADP antagonists
  • PDE and adenosine uptake inhibitors
  • Antiplasmin
75
Q

COX inhibitors

A
  • Aspirin
76
Q

COX inhibitors (aspirin) MOA

A
  • Nonselective, irreversible COX inhibitor

- Reduces platelet production of thromboxane A2

77
Q

COX inhibitors (aspirin) side effects

A
  • Gastrointestinal toxicity
  • Nephrotoxicity
  • Metabolic acidosis
  • Increased leukotrienes
78
Q

GP2b/3a inhibitors generic/brand names

A
  • Abciximab (reoPro)
  • Eptifibatide (Integrilin)
  • Tirofiban (Aggrastat)
79
Q

Abciximab (reoPro) MOA

A
  • Irreversible Inhibits GPIIb/IIIa binding to fibrinogen

- Prevents platelet cross-linking

80
Q

Eptifibatide (Integrilin), tirofiban (Aggrastat) MOA

A
  • Reversibly Inhibits GPIIb/IIIa binding to fibrinogen
81
Q

Abciximab (reoPro) side effects

A
  • Bleeding

- Thrombocytopenia with prolonged use

82
Q

ADP antagonists generic/brand names

A
  • Clopidogrel (Plavix)
  • Ticlopidine (Ticlid)
  • Prasugrel (effient)
  • Ticagrelor (Brilinta)
83
Q

Clopidogrel (Plavix) MOA

A
  • Irreversibly inhibits platelet ADP receptor
84
Q

Clopidogrel (Plavix) Pk

A
  • Prodrug activation by CYP2C9 and CYP2C19
85
Q

Clopidogrel (Plavix) side effetcs

A
  • Bleeding
  • Gastrointestinal disturbances
  • Hematologic abnormalities
86
Q

Ticlopidine (Ticlid) Pk

A
  • Prodrug activation by CYP2C9 and CYP2C19
87
Q

Ticlopidine (Ticlid) side effects

A
  • More toxicity, particularly leukopenia and thrombotic thrombocytopenic purpura (with small thrombi formation)
88
Q

Prasugrel (effient) Pk

A
  • Less variable kinetics

- Activation primarily by CYP3A4

89
Q

Ticagrelor (Brilinta) Pk

A
  • Reversible ADP receptor antagonist

- Does not require activation

90
Q

PDE and adenosine uptake inhibitors generic/brand names

A
  • Dipyridamole

- Cilostazol (Pletal)

91
Q

Dipyridamole, Cilostazol (Pletal) MOA

A
  • Inhibits adenosine uptake

- Inhibits phosphodiesterase (PDE) enzymes that degrade cyclic nucleotides (cGMP: vasodilator)

92
Q

Dipyridamole, Cilostazol (Pletal) side effects

A
  • Headache
  • Palpitations
  • Contraindicated in congestive heart failure
93
Q

Antiplasmin generic/brand names

A
  • Aminocaproic acid (Amicar)

- Tranexamic acid (Lysteda)

94
Q

Aminocaproic acid (Amicar), Tranexamic acid (Lysteda) MOA

A
  • Competitvely inihibit plasminogen activation
95
Q

Aminocaproic acid (Amicar), Tranexamic acid (Lysteda) side effects

A
  • Thrombosis
  • Hypotension
  • Myopathy
  • Diarrhea

Pharmacology (27 decks)

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