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WILLIAM'S HEMATOLOGY > 32 Antithrombotic Therapy > Flashcards

32 Antithrombotic Therapy Flashcards

1
Q

The most common adverse effect of antithrombotics

A

Bleeding

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2
Q

Decrease fibrin formation by inhibiting
thrombin or thrombin formation

A

Anticoagulant

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3
Q

Inhibit platelet function

A

Antiplatelet

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4
Q

Activate plasminogen and accelerate clot
lysis

A

Fibrinolytic agents

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5
Q

Competitive inhibitors of vitamin K

A

Coumarins or VKAs

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6
Q

VKAs MOA: inhibit γ-carboxylation reactions in the posttranslational modification of the coagulation factors ______________as well as the natural inhibitors ___________

A

Coagulation factors II, VII, IX, and X

Proteins C and S

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7
Q

VKA: water soluble and rapidly absorbed after oral administration, reaching a peak concentration after _________ minutes

A

60–90 minutes

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8
Q

Warfarin is metabolized through the _____________-system, the activity of which is influenced by environmental factors and genetic polymorphisms.

A

Cytochrome P450 (CYP) system

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9
Q

Hereditary resistance to warfarin has been described and is related to specific mutations in ______________.

A

vitamin K epoxide reductase

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10
Q

Potentiate effect of VKA

A

Immediate: Acetaminophen

Typically within 1 week:
Ciprofloxacin
Metronidazole
Clarithromycin
Prednisone
Erythromycin
Trimethoprim-sulfamethoxazole

Progressive, prolonged: Amiodarone

Results from combined inhibition of platelet function:
Acetylsalicylic acid (avoid dosing >100 mg)
Nonsteroid antiinflammatory
drugs

Reduced vitamin K intake: Weight reduction diet, Illness and no food intake

Increased warfarin sensitivity: Broad spectrum antibiotics, Liver disease, Hyperthyroidism

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11
Q

Depress effect of VKA

A

Drugs: Barbiturates Phenobarbital Carbamazepine Rifampin Phenytoin Vitamin K

Increase Vitamin K intake: Excess of dark green vegetables, Some enteral feeds

Warfarin resistance: Mutation in VKOR

Decreased warfarin absorption: Diarrhea, Avocado

Decreased metabolism of coagulation factors: Hypothyroidism

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12
Q

Coagulation half life (shortest to longest)

A

Factor VII - 5 hours
Factors X and IX- 24 hours)
Factor II (prothrombin) (72 hours)

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13
Q

TRUE OR FALSE

Because protein C is a natural inhibitor of coagulation with a short half-life (approximately 8 hours), its level may also fall rapidly, theoretically inducing a procoagulant state during initiation of therapy.

A

TRUE

Because protein C is a natural inhibitor of coagulation with a short half-life (approximately 8 hours), its level may also fall rapidly, theoretically inducing a procoagulant state during initiation of therapy.

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14
Q

Smaller amounts of Warfarin should be used for

A

Frail
Elderly
Poorly nourished patients
Those with an increased bleeding risk

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15
Q

During initiation of therapy, the INR is checked every_____________ until a stable therapeutic effect is achieved.

A

every 2–3 days for 1–2 weeks

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16
Q

VKA: The target INR for most indications is _______, with a desirable therapeutic range from ________.

A

2.5

2 to 3

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17
Q

The clearance of warfarin is the result of hepatic metabolism, and _________is the most important enzyme mediating its clearance.

A

CYP2C9

The most important are CYP2C92 and CYP2C93, which are found in approximately 11% and 7% of patients and result in reductions of enzymatic activity of approximately 30% and 80%, respectively.

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18
Q

Converts oxidized vitamin K to the active reduced form as required for posttranslational carboxylation

The target of warfarin, which functions as a competitive inhibitor.

A

VKORC1

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19
Q

Score for Predicting Bleeding Risk on Warfarin

A

HAS-BLED Score

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20
Q

Variable included in HAS-BLED Score

A

Hypertension, abnormal renal or liver function, stroke, prior bleeding complications, labile INR, age older than 65 years, and drug or alcohol abuse

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21
Q

The most important predictor of bleeding risk (HASBLED)

A

INR

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22
Q

Cause of skin necrosis in with warfarin use

A

Disproportionately rapid reduction in proteins C and S

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23
Q

TRUE OR FALSE

Oral anticoagulation should be avoided in pregnancy because warfarin crosses the placenta, and exposure during organogenesis in the second trimester can lead to fetal embryopathy with significant cranial bone malformations.

A

FALSE

Oral anticoagulation should be avoided in pregnancy because warfarin crosses the placenta, and exposure during organogenesis in the first trimester can lead to fetal embryopathy with significant cranial bone malformations.

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24
Q

TRUE OR FALSE

Vitamin K antagonists are safe during lactation

A

TRUE

Vitamin K antagonists are safe during lactation

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25
Q

Reversing Warfarin Therapy

INR <6

A

Lower the dose, consider withholding 1 or more doses

Recheck in 3–7 days

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26
Q

Reversing Warfarin Therapy

INR 6-10

A

Lower the dose and withhold 1–3 doses
Vitamin K, 1–2 mg orally if increased risk
for bleeding

Recheck INR in 24–48 hours

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27
Q

Reversing Warfarin Therapy

INR 6-10

A

Withhold doses until INR is in desired
range and cause of elevation ascertained

Give vitamin K, 2–4 mg orally

Recheck INR in 24 hours

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28
Q

INR >1.5 and serious bleeding

A

Administer four-factor prothrombin complex concentrate if available for rapid
reversal.

If four-factor prothrombin complex
concentrate not available, administer
fresh-frozen plasma.

Also give 5–10 mg vitamin K intravenously

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29
Q

TRUE OR FALSE

Heparin has direct anticoagulant effect and serves to activate plasma antithrombin (AT), a serine protease inhibitor.

A

FALSE

Heparin has no direct anticoagulant effect but serves to activate plasma antithrombin (AT), a serine protease inhibitor.

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30
Q

Half life of heparin

A

1–2.5 hours

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31
Q

Monitoring for heparin

A

Activated partial thromboplastin time (aPTT)
The usual aPTT range for heparin therapy is between 1.5 and 2.5 times the mean of the normal range.

Anti-Xa levels

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32
Q

Considered in patients who does not display an adequately prolonged aPTT after treatment with unfractionated heparin, despite having received apparently adequate or even supratherapeutic doses of the drug

Patients who require heparin doses of more than 35,000 U/day to increase the aPTT into the therapeutic range,

A

Heparin resistance

Usually caused by an acute-phase response that results in high levels of procoagulant proteins, including factor VIII.

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33
Q

TRUE OR FALSE

Monitoring is recommended when low doses of heparin are used for prophylaxis of venous thromboembolic disease

A

FALSE

No monitoring is recommended when low doses of heparin are used for prophylaxis of venous thromboembolic disease

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34
Q

Reversal agent for heparin

A

Protamine sulfate

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35
Q

Dosage of protamine sulfate

A

1 mg to neutralize 100 units of heparin

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36
Q

An immune-mediated platelet consumption caused by an antibody directed against a complex of heparin and platelet factor 4

A

HIT

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37
Q

Scoring used for HIT

A

“4T’ score

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38
Q

Vitamin K antagonists should be given only after the platelet count has risen to higher than ______________-

A

150,000/μL

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39
Q

Difference of LMWH from UFH

A

Greater inhibition of factor Xa than of thrombin

Completely absorbed

Exhibit less binding to plasma proteins and cells

Longer plasma half-life

Significant renal clearance

Protamine sulfate does not completely reverse the anticoagulant effect of LMWH

HIT is much less common

Osteoporosis may be less common

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40
Q

Plasma half-life of Danaparoid

A

24 hours

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41
Q

Clearance of Danaparoid

A

Renal

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42
Q

Monitoring of Danaparoid

A

Anti– factor Xa assays

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43
Q

A unique heparinlike anticoagulant with highly selective AT-dependent anti–factor Xa activity

A

Fondaparinux

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44
Q

TRUE OR FALSE

Fondaparinux is synthesized in a structurally homogenous form containing no animal products.
Consequently, fondaparinux does not induce allergic responses.

A

TRUE

Fondaparinux is synthesized in a structurally homogenous form containing no animal products.
Consequently, fondaparinux does not induce allergic responses.

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45
Q

Fondaparinux: maximum plasma levels are reached approximately ______ hours after subcutaneous administration

A

Two hours

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46
Q

Fondaparinux: half-life

A

17 hours

47
Q

Fondaparinux: half-life

A

17 hours

48
Q

Clearance of Fondaparinux

A

Renal

49
Q

Monitoring of Fondaparinux

A

Anti–factor Xa assay

But there is no effect on other coagulation assays including the activated clotting time (ACT), aPTT, or thrombin clotting time

50
Q

A direct thrombin inhibitor, is a recombinant protein based on the structure of hirudin, is composed of a dodecapeptide analogue of the carboxyterminal region of hirudin linked by a four-glycine residue to a structure directed to the active site of thrombin.

A

Bivalirudin

51
Q

Bivalirudin: half-life

A

30 minutes

52
Q

Monitoring of Bivalirudin

A

ACT and aPTT

53
Q

Clearance of Bivalirudin

A

Renal and hepatic

54
Q

Anticoagulants with no specific antidote

A

Bivalirudin
Argatroban

55
Q

A small-molecule arginine derivative that reversibly and directly inhibits thrombin by binding to the active catalytic site of the enzyme with a Ki of 3.9 × 10−8 mol/L.

A

Argatroban

56
Q

Argatroban: half-life

A

39 to 51 minutes

57
Q

Monitoring of Argatroban

A

aPTT or ACT

58
Q

Clearance of Argatroban

A

Hepatic

59
Q

A DOC which is is a thrombin-inhibitor prodrug with a bioavailability of approximately 6% after oral administration

A

Dabigatran etexilate

60
Q

Dabigatran: half-life

A

12 hours

61
Q

Monitoring of Dabigatran

A

Dilute thrombin time and ecarin clotting time

62
Q

Dabigatran is dependent on the efflux transporter _________for enteral elimination

A

P-glycoprotein (P-gp)

Strong P-gp inducers (ie, rifampicin, carbamazepine, phenytoin, phenobarbital) will reduce the effect

Strong P-gp inhibitors (ie, ketoconazole, itrakonazole, HIV-protease inhibitors, dronedarone) will increase the effect

63
Q

Can inhibit both free- and thrombus-associated factor Xa

A

Rivaroxaban

64
Q

Clearance of Rivaroxaban

A

Renal, hepatic, P-gp transport

65
Q

Rivaroxaban: half-life

A

5.7–9.2 hours

66
Q

Monitoring of Rivaroxaban

A

Rivaroxaban-calibrated anti-Xa assay

PT is more accurate than the aPTT

67
Q

Reversal agent for Rivaroxaban

A

Andexanet alfa

68
Q

Clearance of Apixaban

A

Renal, hepatic, P-gp transport

69
Q

Apixaban: half-life

A

12 hours

70
Q

Monitoring of Apixaban

A

Apixaban-specific anti-Xa assays

PT is more sensitive than aPTT

71
Q

Edoxaban : half-life

A

8 hours.

72
Q

Clearance of Edoxaban

A

Renal, P-gp transport

73
Q

Monitoring of Edoxaban

A

Edoxaban-specific anti-Xa assays

Partial thromboplastin time

74
Q

It has the lowest renal excretion of all direct oral anticoagulants, 11%, and is metabolized by non CYP-hydrolysis.

A

Betrixaban

75
Q

Betrixaban : half-life

A

19–27 hours

76
Q

Uses of fibrinolytic therapy

A

Venous and arterial thrombosis
Acute myocardial infarction
Thrombosis of peripheral arteries, bypass grafts, and catheters
Pulmonary emboli causing hemodynamic compromise

77
Q

The first plasminogen activator used clinically

A

Streptokinase

78
Q

TRUE OR FALSE

Streptokinase has no enzymatic activity, but it combines with plasminogen to form an equimolar streptokinase– plasminogen complex that can then convert other plasminogen molecules to plasmin.

A

TRUE

Streptokinase has no enzymatic activity, but it combines with plasminogen to form an equimolar streptokinase– plasminogen complex that can then convert other plasminogen molecules to plasmin.

79
Q

Streptokinase has a rapid plasma clearance with a half-life of approximately _____ minutes, but the duration of the proteolytic effect is more prolonged.

A

20 minutes

80
Q

Streptokinase is antigenic, and high-titer antibodies develop ______weeks after use, precluding retreatment until the titer declines.

A

1–2 weeks

81
Q

A naturally occurring plasminogen activator that is structurally and immunologically distinct from urokinase

A

Tissue-type plasminogen activator (t-PA)

82
Q

Recombinant tissue-type plasminogen activator (t-PA)

A

Alteplase

83
Q

The half-life of t-PA after intravenous administration is approximately ______ minutes, which requires a constant infusion to maintain therapeutic plasma levels.

A

5 minutes

84
Q

Has enhanced fibrin specificity and a significantly longer half-life of 15 minutes compared with 4 minutes with t-PA, so it can be administered as an intravenous bolus rather than as a continuous infusion

A

Reteplase

85
Q

Useful for prehospital administration in remote areas, or areas with limited access to primary percutaneous coronary interventions

A

Reteplase

86
Q

It has a half-life of more than 30 minutes and can be administered as a single IV bolus.

A

Tenecteplase (TNK)

87
Q

Substance that recruits platelets

A

Adenosine diphosphate (ADP)
Thromboxane A2

88
Q

TRUE OR FALSE

The role of platelets in initiating thrombosis is greater in the arterial circulation than in the venous circulation because higher shear forces that are present in arteries activate platelets.

A

TRUE

The role of platelets in initiating thrombosis is greater in the arterial circulation than in the venous circulation because higher shear forces that are present in arteries activate platelets.

89
Q

CYCLOOXYGENASE INHIBITORS

A

Aspirin

90
Q

AGENTS THAT INCREASE cAMP

A

Dipyridamole
Pentoxifylline
Cilostazol

91
Q

ADP RECEPTOR BLOCKERS

A

Ticlopidine
Clopidogrel
Prasugrel
Ticagrelor

92
Q

ADP mimetic

A

Cangrelor

93
Q

αIIbβ3 inhibitors

A

Abciximab
Eptifibatide
Tirofiban

94
Q

THROMBIN RECEPTOR BLOCKER

A

Vorapaxar

95
Q

It converts arachidonic acid released from membrane phospholipids by phospholipase A2 or phospholipase C and diacylglycerol to prostaglandin (PG) G2

A

Cyclooxygenase (COX)-1

96
Q

A potent inhibitor of platelet function, through an increase in intraplatelet cyclic adenosine monophosphate (cAMP)

A

Prostacyclin

97
Q

Aspirin cause (reversible or irreversible) enzyme inhibition

A

Irreversible

98
Q

Two phosphodiesterase inhibitors that are used primarily in patients with peripheral vascular disease

A

Pentoxifylline and cilostazol

99
Q

Thienopyridines ADP blockers

A

Ticlopidine, clopidogrel, and prasugrel

100
Q

Nonthienopyridines ADP blockers

A

Ticagrelor and cangrelor

101
Q

There are three ADP receptors on platelet membranes, with the thienopyridines inhibiting one of them, the ________receptor.

A

P2Y12 receptor

102
Q

Thienopyridines associated with increased risk of thrombocytopenia and neutropenia.

A

Ticlopidine

103
Q

A “third-generation” P2Y12 blocking agent

Can be converted to its active metabolite via esterases present in either the liver or the gut.

A

Prasugrel

104
Q

Agent that reversibly inhibit the P2Y12 platelet receptor

A

Ticagrelor

105
Q

The first parenteral ADP receptor blocker

A

Cangrelor

106
Q

αIIbβ3 blocker: a cyclic heptapeptide based on a rattlesnake venom peptide

A

Eptifibatide

107
Q

αIIbβ3 blocker: a nonpeptide derivative of tyrosine

A

Tirofiban

108
Q

TRUE OR FALSE

Prohemostatic agents may, at least theoretically, predispose for thrombotic complications.

A

TRUE

Prohemostatic agents may, at least theoretically, predispose for thrombotic complications.

109
Q

A vasopressin analogue that, despite minor molecular differences, has retained its antidiuretic properties but has much fewer vasoactive effects.

Induces release of the contents of the endothelial cell–associated Weibel–Palade bodies, including von Willebrand factor

A

De-amino D-arginine vasopressin (DDAVP, desmopressin)

110
Q

A rare but important adverse effect of DDAVP is the occurrence of_________ , probably a result of the remaining vasoactive effect of the drug.

A

Acute coronary syndromes

111
Q

A 58-amino-acid polypeptide, mainly derived from bovine lung, parotid gland, or pancreas

Directly inhibits the activity of various serine proteases, including plasmin, coagulation factors or inhibitors, and constituents of the kallikrein-kinin and angiotensin system

A

Aprotinin

112
Q

Lysine analogues that competitive bindst o the lysine-binding sites of a fibrin clot

A

ε-aminocaproic acid and tranexamic acid

**tranexamic acid (Cyklokapron) is at least 10 times more potent than ε-aminocaproic acid (Amicar)

113
Q

The use of lysine analogues is contraindicated in

A

Ongoing systemic activation of coagulation (such as in disseminated intravascular coagulation)

In cases of macroscopic hematuria, because the inhibition of urinary fibrinolysis caused by the high concentrations of the antifibrinolytic agent in the urine may result in deposition of urinary tract–obstructing clots.

114
Q

The most significant contraindication of tranexamic acid

A

macroscopic hematuria

WILLIAM'S HEMATOLOGY (89 decks)

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