A prospective randomized study to determine the optimal dose of intravenous vitamin K in reversal of over-warfarinization.
The optimal management of asymptomatic overanticoagulated patients remains unknown. We measured international normalized ratio (INR), activated partial thromboplastin time (APTT) and prothrombin fragment 1 + 2 (F1 + 2) over 7 d in 24 asymptomatic or mildly haemorrhagic patients on warfarin with prolonged INR of > 7.0 who were randomized to receive 0.5 mg, 1 mg or 2 mg intravenous vitamin K. Of six severely overanticoagulated patients (INR > 9.5 with APTT ratio > 2), five failed to achieve an INR < or = 4.0 on day 1, irrespective of vitamin K dose given. In the remaining 18 cases, an optimal response (INR 2-4 at day 1) was observed in 67% of those receiving 0.5 mg vitamin K, but only in 33% of those receiving 1 or 2 mg, the majority of whom developed an INR < 2.0. Our results support an optimal dose of 0.5 mg i.v. vitamin K for most overanticoagulated patients, with possibly a repeat dose in the small group of severely overanticoagulated patients.
Hung
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A
Department of Haematology, Southern General Hospital, Glasgow, UK.
Singh
S
S
Tait
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RC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D004334:Drug Administration Schedule; D062787:Drug Overdose; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011446:Prospective Studies; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin