warfarin (INR ranges and length of treatment in var. conditions)
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  • INR 2-2.5

    • prophylactic treatment for DVT (short-term)

  • INR 2-3

    • prophylactic treatment for hip surgery and surgery for femur fractures (short to medium term)
    • treatment of venous thromboembolism - deep vein thrombosis (DVT) or pulmonary embolism (PE) (1)
      • anticoagulation for 1 month is inadequate treatment after an episode of VTE
      • at least 6 weeks anticoagulation is recommended after calf vein thrombosis and at least 3 months after proximal DVT or PE
      • for patients with temporary risk factors and a low risk of recurrence 3 months of treatment may be sufficient
      • for patients with idiopathic VTE or permanent risk factors at least 6 months anticoagulation is recommended
      • target INR of 2·5 is recommended for long-term oral anticoagulant (VKA) therapy for secondary prevention of VTE
      • target INR of 2·5 is recommended for patients with DVT or PE associated with antiphospholipid syndrome
        • target of 3·5 is also recommended for patients who suffer recurrence of VTE whilst on warfarin with an INR between 2·0 and 3·0
    • cardioversion (1)
      • target INR of 2·5 is recommended for 3 weeks before and 4 weeks after cardioversion
        • to minimise cardioversion cancellations due to low INRs on the day of the procedure a higher target INR, e.g. 3·0, can be used prior to the procedure
    • peripheral arterial thrombosis and grafts
      • antiplatelet drugs remain first line intervention for secondary antithrombotic prophylaxis. If long-term anticoagulation is given to patients at high risk of femoral vein graft failure a target INR of 2·5 is recommended (1)
    • coronary artery thrombosis
      • if oral anticoagulant therapy is prescribed a target INR of 2·5 is recommended (1)
    • systemic embolism after MI
    • mitral stenosis with embolism (long term)
    • atrial fibrillation (long-term) - it may be safer to aim for an INR of 2 in those aged over 75 years (3)
      • risk of stroke is 3 times greater in patients with atrial fibrillation with mitral stenosis than in those without valve disease - based on its apparent effectiveness in non-randomized studies and its effect in non-rheumatic atrial fibrillation, warfarin is usually given to maintain an INR of 2.5 (5)

  • INR 3.0 or more

    • treatment of recurrent DVT, PE (long term)
      • target of 3·5 is also recommended for patients who suffer recurrence of VTE whilst on warfarin with an INR between 2·0 and 3·0
    • prosthetic heart valves (long-term)
      • for patients in whom valve type and location are known specific target INRs are recommended (1)
        • bileaflet valve (aortic) 2·5
        • tilting disk valve (aortic) 3·0
        • bileaflet valve (mitral) 3·0
        • tilting disk (mitral) 3·0
        • caged ball or caged disk (aortic or mitral) 3·5
      • otherwise a target INR of 3·0 is recommended for valves in the aortic position and 3·5 in the mitral position (1)

Notes (1):

  • bioprosthetic valves:

    • long-term warfarin not required in absence of atrial fibrillation
    • oral anticoagulants are not required for valves in the aortic position in patients in sinus rhythm, although many centres anticoagulate patients for 3?6 months after any tissue valve implant
      • patients with bioprostheses in the mitral position should receive oral anticoagulants to achieve an INR of 2.5 for the first 3 months. After 3 months, patients with atrial fibrillation should receive lifelong therapy to achieve an INR of 2.5
      • patients with bioprosthetic valves with a history of systemic embolism and those with intracardiac thrombus should also be anticoagulated to achieve an INR of 2.5
      • patients who do not require oral anticoagulants after the first 3 months may be considered for antiplatelet therapy, e.g. aspirin

  • INR values and risk of haemorrhage versus risk of thromboembolism in treatment of DVT/PE
    • risks of haemorrhage and thromboemboli are minimized at international normalized ratios of 2-3. Ratios that are moderately higher than this therapeutic range appear safe and more effective than subtherapeutic ratios (6)

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