Anticoagulation (paediatrics)

Prescribing Notes:

• The warfarin dose is adjusted according to the international normalised ratio (INR). The target INR should be clearly identified at initiation of therapy, and measured daily or on alternate days initially, then at longer intervals (depending on response) then up to every 12 weeks.
• Indication and duration of treatment should be clearly recorded at initiation of treatment; the patient-held anticoagulant treatment booklet should be used. See BNFc for details.
• The plasma half-life of warfarin is 35 hours; a steady anticoagulant effect is achieved after about one week. If immediate anticoagulation is required, heparin or LMWH must be given concomitantly.
• There are many clinically important interactions with warfarin; clinicians are strongly advised to consult BNFc before prescribing.
• Vitamin K (phytomenadione) can be given to reverse the effects of warfarin but takes 6-12 hours to become effective. Immediate reversal of the anticoagulant effect of warfarin may be achieved with prothrombin complex concentrate or (if no concentrate available) fresh frozen plasma; see BNFc for details. Specialist haematological advice should be sought.
• Cardiac patients on warfarin should have doses adjusted by cardiology consultants.