A prospective randomized study to determine the optimal dose of intravenous vitamin K in reversal of over-warfarinization

Br J Haematol. 2000 Jun;109(3):537-9. doi: 10.1046/j.1365-2141.2000.02001.x.

Abstract

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.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anticoagulants / adverse effects*
  • Anticoagulants / therapeutic use
  • Drug Administration Schedule
  • Drug Overdose
  • Female
  • Humans
  • Infusions, Intravenous
  • International Normalized Ratio
  • Male
  • Middle Aged
  • Partial Thromboplastin Time
  • Prospective Studies
  • Vitamin K / administration & dosage*
  • Warfarin / adverse effects*
  • Warfarin / therapeutic use

Substances

  • Anticoagulants
  • Vitamin K
  • Warfarin