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Related Experiment Videos

A randomized trial comparing 5-mg and 10-mg warfarin loading doses

M A Crowther1, J B Ginsberg, C Kearon

  • 1Hamilton Civic Hospitals Research Centre, Ontario, Canada. crowthrm@fhs.csu.mcmaster.ca

Archives of Internal Medicine
|January 19, 1999
PubMed
Summary

A 5-mg warfarin loading dose is as effective as a 10-mg dose for achieving therapeutic international normalized ratio (INR) levels. This finding suggests a lower loading dose may be preferable for warfarin initiation, reducing overanticoagulation risks.

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Area of Science:

  • Pharmacology
  • Clinical Pharmacy
  • Internal Medicine

Background:

  • Warfarin sodium therapy commonly uses loading doses to expedite therapeutic international normalized ratio (INR) elevation.
  • However, loading doses are linked to early overanticoagulation and potential hypercoagulable states, without guaranteed faster achievement of target INR.
  • This study aimed to validate the efficacy of a 5-mg warfarin loading dose compared to a 10-mg dose.

Purpose of the Study:

  • To prospectively compare the effectiveness of 5-mg versus 10-mg warfarin sodium loading doses.
  • To determine if a lower loading dose can achieve a therapeutic INR (2.0-3.0) for two consecutive days.
  • To assess the incidence of overanticoagulation with different warfarin loading doses.

Main Methods:

  • A prospective randomized study involving 53 patients initiating warfarin therapy.

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  • Patients were assigned to receive either a 5-mg or 10-mg initial warfarin dose.
  • INR was monitored daily for 5 days, with the primary endpoint being consecutive therapeutic INR values without exceeding 3.0.

    • Main Results:

    • Significantly more patients in the 5-mg group (66%) achieved the primary endpoint compared to the 10-mg group (24%).
    • The 5-mg group showed a trend toward less overanticoagulation.
    • The relative risk for achieving the primary endpoint was 2.22 (95% CI, 1.30-3.70; P < .003) in favor of the 5-mg dose.

    Conclusions:

    • A 5-mg warfarin loading dose is as effective as a 10-mg dose in achieving therapeutic INR levels by day 4 or 5.
    • The findings suggest that a 5-mg loading dose may be a suitable alternative to the 10-mg dose.
    • Lowering the initial warfarin dose could potentially reduce risks associated with overanticoagulation.