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M2: Cardiology > Anti-Platelet and Anti-Coagulant Drugs (Lobel) - 11/7/16 > Flashcards

Anti-Platelet and Anti-Coagulant Drugs (Lobel) - 11/7/16 Flashcards

1
Q

Heparin

Heparin administration

Heparin vs Heparan Sulfate

A

Indirect thrombin inhibitor

Heparin = Antithrombin III activator (inhibits Xa)

Administration:

  • NOT absorbed from GI tract – not effective orally
  • Does not cross placenta or accumulate in milk of nursing mothers
  • IV route for treatment of patients w/ active thrombosis or PE

Heparan Sulfate = component of ECM (not as strong of anticoag effect)

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2
Q

Antithrombotic mechanisms (4) 1/3

A
  1. Intact endothelium
    1. Separates plasma factor VII from subendothelial tissue factor
  2. Blood flow
    1. Clears activated coagulation factors
  3. Prostacyclin (PGI2)
    1. Inhibits platelets
  4. t-PA
    1. Activates plasminogen
    2. Plasmin degrades fibrin
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3
Q

Antithrombotic mechanisms (2/3)

antithrombin (ATIII)

A
  • Natural blood thinner
  • Antithrombin inhibits
    • Thrombin (IIa)
    • Factor Xa
    • Factor IXa
  • Activated by: endothelial cell heparan sulfate
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4
Q

Antithrombotic mechanisms (3/3)

Protein C / Protein S / Thrombomodulin

A
  • Degrade factors Va and VIIIa
  • Protein C or S deficiency → Inc. risk for venous thrombosis
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5
Q

Complications of heparin therapy

A
  • Major bleeding (5-10 day course)
  • Osteoporosis
  • Heparin resistance
  • Heparin-induced thrombocytopenia (deficiency of platelets in blood)
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6
Q

Indirect thrombin inhibitors:

Heparin

Enoxaparin

Fondaparinux

A

Enoxaparin

  • Compared to heparin
    • Less inhibition of thrombin
    • Efficiently inhibit factor Xa activity
    • Less effect on vascular permeability
    • Less bound to plasma proteins
    • Longer half life (~4.5 h), less frequent dosing
    • Contraindicated in patients with HIT
  • Typically used in:
    • Prevention of DVT in postop period
    • Treatment of acute venous thromboembolic disease and acute coronary syndromes

Fondaparinux

  • Long half-life (17-21 h)
  • 100% bioavailable after single, daily, subcutaneous dose
  • Renal clearance, should not be given to patients with renal impairment
  • Does not cause HIT
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7
Q

Direct thrombin inhibitors- parenteral

Desirubin

Bivalirudin

Argatroban

A

Desirubin

  • 65 aa protein found in medicinal leech
  • Most potent known inhibitor of thrombin
  • Action is independent of antithrombin III
  • Does not cause thrombocytopenia
  • Renal clearance
  • Bind catalytic site and exosite I of thrombin

Bivalirudin

  • Short half life (~25 min)
  • Clearance: renal and metabolic
  • Bind catalytic site and exosite I of thrombin

Argatroban

  • Used as anticoagulant in patients with heparin-induced thrombocytopenia (HIT)
  • Half life: 40-50 min
  • Binds only at active site of thrombin
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8
Q

Oral Anticoagulant

Warfarin

A
  • Inhibits biosynthesis of vitamin K-dependent zymogens
    • Procoagulant:
      • Prothrombin
      • Factor VII
      • Factor IX
      • Factor X
    • Anticoagulant:
      • Protein C
      • Protein S
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9
Q

Warfarin mechanism

A
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10
Q

Adverse effects of Warfarin therapy

A
  • Bleeding
  • Birth defects and abortion​
    • ​Skeletal and CNS abnormalities (hypoplastic nose, flat face, altered calcification)
    • Contraindicated during pregnancy (heparin may be used)
  • Skin necrosis
    • ​Microvascular thrombosis
    • May occur in patients with heterozygous protein C or S deficiency if high initial dose is used or heparin overlap is inadequate
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11
Q

New/Novel Direct Oral Anticoagulants (NOACs)

Dabigatran: thrombin inhibitor

Rivaroxaban, Apixaban, Edoxaban: Xa inhibitors

A
  • Non-inferiority/superiority to Warfaran
  • Similar/less intracranial bleeding
  • Similar overall bleeding
  • Similar uses to warfarin but not approved for thrombus prophylaxis with synthetic heart valves
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12
Q

Fibrinolysis

A

Process of breaking down fibrin

Conversion of plasminogen to plasmin

Physiologically, activity of activated plasmin is restrict to the clot

  • Activators are effective mainly on plasminogen absorbed to fibrin
  • Plasmin which escape into circulation is inactivated
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13
Q

Fibrinolytic drugs:

Altephase

Half-life

Approved uses

A

Alteplase: recominbant tissue plasminogen activity (tPA)

Half-life: ~5 min in plasma

Approved uses:

  • Acute MI
  • Acute ischemic stroke
  • PE
  • Central venous catheter occlusion
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14
Q

Contraindications to fibrinolytic therapy

A
  • Prior intracranial hemorrhage
  • Known structural cerebral vascular lesion
  • Known malignant intracranial neoplasm
  • Ischemic stroke within 3 months
  • Suspected aortic dissection
  • Active bleeding (excluding menses)
  • Significant closed-head trauma or facial trauma within 3 mo
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15
Q

Antiplatelet agents

Drug targets (3)

A
  • Inhibition of prostaglandin metabolism
  • Inhibition of ADP-induced platelet aggregation
  • BLockage of GP IIb/IIIa receptors on platelets
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16
Q

Aspirin

A

Mechanism of action: cyclooxygenase (COX) inhibitor

17
Q

ADP receptor antagonists

A
18
Q

Platelet GP IIb/IIIa receptor blockers

A

M2: Cardiology (13 decks)

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