Significant controversy exists concerning how best to reverse excessive anticoagulation (due to warfarin sodium therapy) with phytonadione (vitamin K1) while avoiding overcorrection in patients who need to have anticoagulation therapy maintained.
A retrospective review of phytonadione use in reversing excessive anticoagulation was performed in 3 institutions. The effectiveness of low-dose (≤0.5 mg) intravenous (LDIV), high-dose (1-10 mg) intravenous (HDIV), subcutaneous (1-10 mg) (SC), and oral (2.5 or 5 mg) (PO) phytonadione was evaluated within 48 hours of administration. Anticoagulation correction (international normalized ratio [INR], ≥2.0 and ≤5.0) occurred in 5 of 8 patients in the LDIV, 5 of 9 in the HDIV, 7 of 10 in the SC, and 5 of 6 in the PO groups. Correction was inadequate (INR >5.0) in 2 of 8 patients in the LDIV, 0 of 9 in the HDIV, 3 of 10 in the SC, and 1 of 6 in the PO groups. Overcorrection (INR <2.0) occurred in 1 patient in the LDIV, 4 patients in the HDIV, 0 in the SC, and 0 in the PO groups.
Anticoagulation correction was achieved in most patients in all 4 groups. The HDIV method was most effective in lowering the INR to less than 5.0, but overcorrection occurred more frequently (4 patients in the HDIV vs 1 patient in the LDIV and 0 patients in the SC and PO groups). Failure to achieve an INR of less than 5.0 was a greater problem in the SC group (3 patients in the SC vs 2 patients in the LDIV and 1 patient in the PO groups). The LDIV and PO methods appear to be acceptable alternatives to the HDIV and SC methods currently recommended.