Anti-Coagulant Drugs Flashcards

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1
Q

List the common anti-coagulants used

A

Unfractionated heparins
Low molecular weight heparins (LMWH)
Vitamin K antagonists / Warfarin
DOACs (direct oral anti-coagulants)

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2
Q

List the following for: Unfractionated heparins

  • Use
  • Example drugs
  • Drug class
  • Mechanism of action
  • Adverse effects
  • Warnings / contraindications
  • Important drug reactions
A

Anti-Coagulant

  • Prevent venous thromboembolism – DVT or PE or perioperative prophylaxis
  • During pregnancy
  • Acute coronary syndromes

Unfractionated heparin

Heparin

Large glycosaminoglycan chains (mixture) - unpredictable

  • Bind to antithrombin-3 and increase its activity (by causing a conformational change)
  • Antithombin-3 then binds to factor 10a – inhibiting factor 10a
  • In order to inhibit thrombin, heparin needs to bind simultaneously to antithrombin-3 and thrombin
  • Bruising and bleeding
  • Heparin-induced thrombocytopenia
  • Hyperkalaemia
  • Osteoporosis
  • Clotting disorders
  • Renal impairment
  • Other anti-thrombotic drugs
  • ACEi/ARB
  • Amiloride / Spironolactone
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3
Q

List the following for: Low molecular weight heparins (LMWH)

  • Use
  • Example drugs
  • Drug class
  • Mechanism of action
  • Adverse effects
  • Warnings / contraindications
  • Important drug reactions
A

Anti-Coagulant

  • Prevent venous thromboembolism – DVT or PE or perioperative prophylaxis
  • During pregnancy
  • Acute coronary syndromes

Dalteparin
Enoxaparin
Fondaparinux – longer t ½

Heparin

Typically smaller polysaccharide chains – more predictable

  • Bind to antithrombin-3 and increase its activity (by causing a conformational change)
  • Antithombin-3 then binds to factor 10a – inhibiting factor 10a
  • Doesn’t inactivate thrombin
  • Bruising and bleeding
  • Heparin-induced thrombocytopenia
  • Hyperkalaemia
  • Osteoporosis
  • Clotting disorders
  • Renal impairment
  • Other anti-thrombotic drugs
  • ACEi/ARB
  • Amiloride / Spironolactone
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4
Q

List the following for: Vitamin K antagonists

  • Use
  • Example drugs
  • Drug class
  • Mechanism of action
  • Adverse effects
  • Warnings / contraindications
  • Important drug reactions
A

Anti-Coagulant

  • Prevent venous thromboembolism – DVT or PE or superficial vein thrombosis
  • AF or cardioversion
  • Heart valve replacement

Warfarin

Vitamin K Antagonists

  • Inhibit activation of vitamin K dependent clotting factors
  • Inhibits conversion of vitamin K to active reduced form (competitive inhibition of VKOR = vitamin K epoxide -> vitamin K)
  • Prevents synthesis of clotting factors which require vitamin K:
    factors 2, 7, 9 and 10
    But delay in onset of action and CYP2C9 polymorphism
  • BLEEDING – epistaxis and spontaneous retroperitoneal bleeding
  • Teratogenic in 1st trimester, haemorrhage risk in 3rd trimester
  • Affected by diet (vitamin K rich foods)

LOTS – most increase Warfarin action, but some decrease Warfarin action

  • Reduce hepatic metabolism – Amiodarone, Clopidogrel, intoxicating alcohol
  • Reduce vitamin K - Cephalosporin
  • Displace Warfarin from albumin – NSAIDs
  • Accelerate Warfarin metabolism – Barbiturates, Phenytoin, Rifampicin, St Johns Wort
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5
Q

List the following for: DOACs (direct oral anti-coagulants)

  • Use
  • Example drugs
  • Drug class
  • Mechanism of action
  • Adverse effects
  • Warnings / contraindications
  • Important drug reactions
A

Anti-Coagulant

Apixaban
Edoxaban
Rivaroxaban
Dabigatran - direct thrombin inhibitor

DOAC (direct oral anticoagulant)

Direct factor Xa:
- Inhibits both free factor Xa and factor Xa bound with antithrombin-3 (doesn’t affect thrombin)
Direct thrombin - Dabigatran:
- Selective direct competitive inhibition of thrombin, circulating and thrombus bound

  • Bleeding – esp. in GI bleed risk groups
  • Dabigatran – not for low creatinine clearance (poor renal function)
  • Avoid in pregnancy and breastfeeding

CYP inhibitors and inducers

  • Increase plasma DOAC – Carbamazepine, Phenytoin and Barbiturates
  • Decrease plasma DOAC - Macrolides
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6
Q

List the antidotes for the following drugs:

  • Heparins
  • Warfarin
  • DOACs
A

Heparins:
Protamine Sulphate
Forms inactive complex with heparin (disassociates heparin from antithrombin-3)
More of an effect with UF than LMWH

Warfarin:
Vitamin K1

DOACs:

  • Andexanet (VERY expensive)
  • Idarucizumab
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