Anti-platelets/ Anti-coagulants

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Anti-platelets/ Anti-coagulants
2012-01-25 15:57:07
SAHD pharmacology common drugs

Top 50 drugs
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  1. What are the indications for aspirin?
    Mild to moderate pain: Headaches and transient musculoskeletal pain. Pyrexia and anti-platelet action.
  2. What is the mode of action of aspirin?
    Irreversible inactivation of the COX-1 enzyme required for prostaglandin and thromboxane synthesis. Blocking Thromboxane A2 prevent platelet aggregation.
  3. What are the contraindications for prescribing aspirin?
    • Children <16 years.
    • Peptic ulceration (past and active)
    • Haemophilia

    • NSAID sensitivity
    • Avoid in hepatic and renal impairment.
    • Avoid towards end of pregnancy or whilst breastfeeding.
  4. What are the side effects of aspirin?
    • GI irritation.
    • Increased bleeding time.
    • Bronchospasm
    • Skin reactions
  5. What is the dose and potential routes of administration of aspirin?
    Oral: 300-900mg every 4-6 hours (max 4g)

    Rectal: 450-900mg every 4 hours (max 3.6g)

    • For long-term anti-platelet action:
    • 75mg OD
  6. How can we reduce side effects of aspirin?
    Take after food or enteric coated capsules (slower delivery)
  7. Does Aspirin interact with other drugs?
    Use with other NSAIDs can increase side effects.

    Increased risk of bleeding if given with anticoagulants, antidepressants, clopidogrel, steroids, iloprost
  8. What is Clopidogrel given for?
    Anti-platelet activation:

    Preventing atherothrombotic event in arterial disease, post-MI or stroke, or during active ACS event.
  9. What is the mode of action of Clopidogrel
    Irreversibly inhibits binding of ADP to a receptor on platelets, inhibiting activation and up-regulation of GP IIb/IIIa receptors which prevents platelet aggregation
  10. What are the contra-indications to prescribing Clopidogrel?
    Active bleeding

    Caution in hepatic and renal impairment, or at risk of bleeding

    Avoid in Pregnancy/ breastfeeding
  11. What are the side effects of Clopidogrel?
    GI discomfort, Bleeding and rare neutropenia

    Due to MOA it can take several days for anti-platelet effects to wear off.
  12. What dose should be prescribed of Clopidogrel?
    • Oral preparations
    • Prevention: 75mg OD

    ACS: 300mg then 75mg daily (600mg loading dose in STEMI)
  13. What is Enoxaparin?
  14. Why is LMWH preferred to unfractionated heparins?
    Same efficacy and longer action, but reduced risk of heparin-induced thrombocytopenia
  15. What is enoxaparin used for?
    • Venous Thromboprophylaxis
    • DVT and PE treatment
  16. What is the mode of action of enoxaparin?
    Accelerates action of anti-thrombin III, increasing the inactivation of Factor Xa (prevents conversion of prothrombin to thrombin)
  17. How would you treat an enoxaparin overdose?
    Protamine (50mg max)
  18. What is the dose of enoxaparin?
    In VTE prophylaxis: 1.5mg/kg OD sub-cut for 5/7

    For NSTEMI/UA: 1mg/kg BD

    For STEMI: none if patient is for PCI
  19. What is HITTS?
    Heparin-induced thrombocytopenia and thrombosis syndrome
  20. Is it ok to give heparin if there is a previous episode of HITTS?
  21. What other LMWHs are available?
    Tinzaparin, Dalteparin
  22. What is the mode of action of warfarin?
    Inhibits Vitamin K reductase, preventing activation of Factors 10, 9, 7, 2 and therefore blood coagulation
  23. What is warfarin indicated for?
    DVT, PE, AF and prosthetic valves if at risk of embolisation
  24. What are the contraindications for prescribing Warfarin?
    • Pregnancy
    • Bleeders
    • Active Ulcers
  25. How is it administered?
    • Takes >3 days for therapeutic effect.
    • LMWH cover should be given until this is reached as it may leave the patient in a pro-thrombotic state.
  26. What are the side effects of warfarin?
    Bleeding, N+V, Diarrhoea, Jaundice, liver dysfunction, pancreatitis, pyrexia, alopecia, 'purple toes'
  27. How could you assess a patient for risk of VTE and whether warfarin would be needed?
    CHADS VASC score
  28. What target INR would a patient on warfarin have?
  29. What baseline tests need to be done for a patient before starting warfarin?
    • FBC
    • LFT
    • INR
  30. What should a patient's platelets be above before warfarin could be prescribed?
  31. How can a patient be started on Warfarin?
    1) Rapid in-patient

    2) Rapid out-patient

    3) Slow out-patient
  32. Does warfarin interact with other drugs?
    Many! See BNF