Warfarin reversal: Consensus guidelines on behalf of the Australasian Society of Thrombosis and Haemostasis

• For most warfarin indications, the target maintenance international normalised ratio (INR) is 2-3. • Risk factors for bleeding complications with warfarin use include age, history of past bleeding and specific comorbid conditions. • To reverse the effects of warfarin, vitamin K₁ can be given. Immediate reversal is achieved with a prothrombin complex concentrate (PCC) and fresh frozen plasma (FFP). Vitamin K₁ is essential for sustaining the reversal achieved by PCC and FFP. • When oral vitamin K₁ is used for warfarin reversal, the injectable formulation of vitamin K₁ is preferable to tablets because of its flexible dosing; this formulation can be given orally or injected. • To temporarily reverse the effect of warfarin when there is a need to continue warfarin therapy, vitamin K₁ should be given in a dose that will quickly lower the INR to a safe, but not subtherapeutic, range and will not cause resistance once warfarin is reinstated. • Prothrombinex-HT is the only PCC approved in Australia and New Zealand for warfarin reversal. It contains factors II, IX and X, and low levels of factor VII. FFP should be added to Prothrombinex-HT as a source of factor VII when used for warfarin reversal. • Simple dental or dermatological procedures may not require interruption to warfarin therapy. • If necessary, warfarin therapy can be withheld 5 days before elective surgery, when the INR usually falls to below 1.5 and surgery can be conducted safely. • Bridging anticoagulation therapy for patients at high risk for thromboembolism should be undertaken in consultation with the relevant experts.