REVERSAL OF WARFARIN.
The reversal agent used for warfarin is a synthetic preparation of phytomenadione (vitamin K1). The presence of vitamin K is essential for formation of prothrombin, factor 7, factor 9 and factor 10.
• Major bleeding – stop warfarin sodium; give 5 mg phytomenadione (vitamin K1) by intravenous injection; give four-factor prothrombin complex (factors 2, 7, 9 and 10); if prothrombin complex unavailable, fresh-frozen plasma can be given but is less effective.
• INR > 8.0, minor bleeding – stop warfarin sodium; give 1–3 mg phytomenadione (vitamin K1) by slow IV injection; repeat dose of phytomenadione if INR still too high after 24 hours; restart warfarin sodium when INR < 5.0.
phytomenadione (vitamin K1) by mouth using the IV preparation orally; repeat dose of phytomenadione if INR still too high after 24 hours; restart warfarin when INR < 5.0.
• INR 5.0–8.0, minor bleeding – stop warfarin sodium; give
1–3 mg phytomenadione (vitamin K1) by IV injection; restart
warfarin sodium when INR < 5.0.
• INR 5.0–8.0, no bleeding – withhold one or two doses of
warfarin sodium and reduce subsequent maintenance dose.
• Unexpected bleeding at therapeutic levels – always investigate possibility of underlying cause, e.g. unsuspected renal or gastrointestinal tract pathology.
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