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Pharmacology > 21) Anti-Coagulants > Flashcards

21) Anti-Coagulants Flashcards

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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
LMWH side effects
- Less risk of HIT | - US Box warning: epidural hematoma
26
LMWH characteristics
- More reliable pharmacokinetics with renal elimination | - Protamine reversal only partially effective
27
LMWH DOA and OOA
- OOA = 1-2 h | - MOA = 12 h
28
Fondaparinux (Arixtra)
- Not considered fully a heparin | - Has common moiety with heparin
29
Fondaparinux (Arixtra) MOA
- Selectively binds to antithrombin III | - Poteniates the neutralization of activated factor Xa
30
Fondaparinux (Arixtra) side effects
- Anemia | - Very low association with HIT
31
Fondaparinux (Arixtra) characteristics
- Protamine does not affect fondaparinux | - OOA = 2-3 h
32
Direct thrombin inhibitors generic/brand names
- Bivalirudin (Angiomax) - Argatroban - Dabigatran (Pradaxa)
33
Bivalirudin (Angiomax) MOA
- Binds to thrombin active site and thrombin substrate
34
Bivalirudin (Angiomax) Pk
- Immediate onset | - DOA = 1-2 h
35
Bivalirudin (Angiomax), Argatroban, and Dabigatran (Pradaxa) side effects (ALL)
- Bleeding (monitor aPTT) - Chest pain - Hypotension
36
Argatroban MOA
- Solely binds to thrombin
37
Argatroban Pk
- Immediate onset | - DOA = 1-2 h
38
Dabigatran (Pradaxa) MOA
- Binds to thrombin active site and thrombin substrate
39
Dabigatran (Pradaxa) Pk
- Only PO
40
Dabigatran (Pradaxa) characteristics
- Idaricizumab binds to dabigatran and reverse its effect - US. Box warning: Premature discontinuation of dabigatran Increases the risk of thrombotic events
41
Direct Xa inhibitors generic/brand names
- Rivaroxaban (Xarelto) - Apixaban (Eliquis) - Edoxaban (Savaysa)
42
Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all have the same MOA
- Binds to Xa active site
43
Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all have the same Pk
- Substrate of CYP450 - Fixed dose PO: no monitoring required - Peak = 2-4 h
44
Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) all characteristics
- US. Box warning: epidural hematoma
45
Coumarin anticoagulants generic/brand names
- Warfarin (Coumadin)
46
Coumarin anticoagulants action
- 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
The action of warfarin can be reversed with
- Vitamin K | - Recovery requires the synthesis of new normal clotting factors and is slow (6–24 h)
48
Warfarin side effects
- Bleeding (US Box warning) | - Early on period of hypercoagulability with subsequent dermal vascular necrosis can occur (due inhibition of protein C)
49
Warfarin characteristics
- Narrow therapeutic window - Substrate of CYP2C9 (patients with genetic variability have dose algorithms) - Renally excreted
50
Warfarin has a delayed onset and offset of anticoagulant activity
- OOA: 1-3 days | - DOA: 2-5 days
51
Heparin vs. warfarin structure
- Heparin = large polysaccharide | - Warfarin = small lipid soluble
52
Heparin vs. warfarin route
- Heparin = parenteral | - Warfarin = oral (PO)
53
Heparin vs. warfarin site of action
- Heparin = blood | - Warfarin = liver
54
Heparin vs. warfarin onset
- Heparin = rapid (minutes) | - Warfarin = slow (days)
55
Heparin vs. warfarin MOA
- 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
Heparin vs. warfarin monitoring
- Heparin = aPTT for unfractionated heparin but not LMW heparins - Warfarin = prothrombin time (PT)
57
Heparin vs. warfarin antidote
- Heparin = Protamine (UH) | - Warfarin = Vitamin K
58
Heparin vs. warfarin use
- Heparin = acute | - Warfarin = chronic
59
Heparin vs. warfarin use in pregnancy
- Heparin = yes | - Warfarin = no
60
Plasmin
- Fibrinolytic enzyme | - Degrades clots by splitting fibrin and fibrinogen in fragments
61
Thrombolytic enzymes
- Catalyze the conversion of the inactive precursor, plasminogen, to plasmin
62
t-PA enzyme
- Directly converts plasminogen to plasmin
63
Tissue plasminogen activators generic/brand names
- Alteplase (Activase) - Reteplase (Retavase) - Tenecteplase (TNKase)
64
Alteplase (Activase) DOA
- 1 h
65
Reteplase (Retavase) OOA/DOA
- OAA = 30-90 minutes - DOA = ? - Faster onset and longer DOA than others
66
Tenecteplase (TNKase) DOA
- Longer DOA than others
67
Alteplase (Activase), Reteplase (Retavase), Tenecteplase (TNKase) side effects (ALL)
- Bleeding | - Cerebral hemmhorrage
68
Streprokinase can induce severe allergic reactions
- It can produce antibodies | - Patients who had streptococcal infections may have antibodies to streprokinase
69
Urokinase is human derived
- No allergy problem, but more expensive
70
Protein synthesized by streptococci
- Streptokinase | - Does not show selectivity for fibrin-bound plasminogen.
71
Thrombus is formed on a damaged vascular wall. Platelets are triggered by a variety of endogenous mediators:
- Glycoprotein (GP) Ia receptor (binds to collagen) - Glycoprotein (GP) Ib receptor (binds to von Willebrand factor) - GP IIb/IIIa (binds fibrinogen)
72
ADP, TXA2 and serotonin
- Aggregating substances that degranulate platelets
73
Substances that increase intracellular cyclic adenosine monophosphate
- Prostaglandin prostacyclin - Adenosine - They inhibit platelet aggregation
74
Antiplatelet drug classes
- COX inhibitors - GP2b/3a inhibitors - ADP antagonists - PDE and adenosine uptake inhibitors - Antiplasmin
75
COX inhibitors
- Aspirin
76
COX inhibitors (aspirin) MOA
- Nonselective, irreversible COX inhibitor | - Reduces platelet production of thromboxane A2
77
COX inhibitors (aspirin) side effects
- Gastrointestinal toxicity - Nephrotoxicity - Metabolic acidosis - Increased leukotrienes
78
GP2b/3a inhibitors generic/brand names
- Abciximab (reoPro) - Eptifibatide (Integrilin) - Tirofiban (Aggrastat)
79
Abciximab (reoPro) MOA
- Irreversible Inhibits GPIIb/IIIa binding to fibrinogen | - Prevents platelet cross-linking
80
Eptifibatide (Integrilin), tirofiban (Aggrastat) MOA
- Reversibly Inhibits GPIIb/IIIa binding to fibrinogen
81
Abciximab (reoPro) side effects
- Bleeding | - Thrombocytopenia with prolonged use
82
ADP antagonists generic/brand names
- Clopidogrel (Plavix) - Ticlopidine (Ticlid) - Prasugrel (effient) - Ticagrelor (Brilinta)
83
Clopidogrel (Plavix) MOA
- Irreversibly inhibits platelet ADP receptor
84
Clopidogrel (Plavix) Pk
- Prodrug activation by CYP2C9 and CYP2C19
85
Clopidogrel (Plavix) side effetcs
- Bleeding - Gastrointestinal disturbances - Hematologic abnormalities
86
Ticlopidine (Ticlid) Pk
- Prodrug activation by CYP2C9 and CYP2C19
87
Ticlopidine (Ticlid) side effects
- More toxicity, particularly leukopenia and thrombotic thrombocytopenic purpura (with small thrombi formation)
88
Prasugrel (effient) Pk
- Less variable kinetics | - Activation primarily by CYP3A4
89
Ticagrelor (Brilinta) Pk
- Reversible ADP receptor antagonist | - Does not require activation
90
PDE and adenosine uptake inhibitors generic/brand names
- Dipyridamole | - Cilostazol (Pletal)
91
Dipyridamole, Cilostazol (Pletal) MOA
- Inhibits adenosine uptake | - Inhibits phosphodiesterase (PDE) enzymes that degrade cyclic nucleotides (cGMP: vasodilator)
92
Dipyridamole, Cilostazol (Pletal) side effects
- Headache - Palpitations - Contraindicated in congestive heart failure
93
Antiplasmin generic/brand names
- Aminocaproic acid (Amicar) | - Tranexamic acid (Lysteda)
94
Aminocaproic acid (Amicar), Tranexamic acid (Lysteda) MOA
- Competitvely inihibit plasminogen activation
95
Aminocaproic acid (Amicar), Tranexamic acid (Lysteda) side effects
- Thrombosis - Hypotension - Myopathy - Diarrhea

Pharmacology (27 decks)

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