What question did this study set out to answer?

To evaluate and compare the impact of 5-mg and 10-mg loading doses of warfarin on laboratory markers of anticoagulant effect.

January 15, 1997Annals of Internal Medicine

Comparison of 5-mg and 10-mg Loading Doses in Initiation of Warfarin Therapy

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Why the study?

Does a 10-mg loading dose of warfarin compared to a 5-mg loading dose increase excess anticoagulation in patients requiring warfarin therapy?

Population

49 patients seen over a 5-month period with a target international normalized ratio of 2.0 to 3.0 at a…

Comparison

10 mg initial loading dose of warfarin, with… vs 5 mg initial loading dose of warfarin, with…

Design

RCT, Randomly assigned

Follow-up

5 days

Authors

LHLinda HarrisonUniversity of Findlay

Discussion

Member takes

Implication

Supports 5-mg over 10-mg warfarin loading to limit excess anticoagulation; challenges higher initial doses in routine initiation.

Key Points

To evaluate and compare the impact of 5-mg and 10-mg loading doses of warfarin on laboratory markers of anticoagulant effect.
Randomized clinical trial conducted over 5 months at a tertiary care teaching hospital involving 49 patients with a target international normalized ratio (INR) of 2.0 to 3.0.
Patients were randomized to receive an initial dose of 5 mg (n=24) or 10 mg (n=25) of warfarin, with subsequent adjustments made via dosing nomograms.
Daily measurements of INR, protein C, and coagulation factors II, VII, IX, and X were tracked across a 5-day period.
At 36 hours, INR > 2.0 occurred in 44% (11/25; 95% CI, 34% to 54%) of the 10-mg group versus 8% (2/24; 95% CI, 3% to 14%) of the 5-mg group (P = 0.005), corresponding to factor VII levels of 27% (95% CI, 18% to 36%) versus 54% (95% CI, 43% to 65%; P < 0.001) and factor II levels of 74% (95% CI, 67% to 81%) versus 82% (95% CI, 73% to 93%; P > 0.2).
At 60 hours, 36% (9/25; 95% CI, 17% to 54%) of the 10-mg group exceeded an INR of 3.0 compared to 0% in the 5-mg group, with 4 patients versus 1 patient requiring vitamin K for excessive anticoagulation.
At 84 hours, therapeutic target INRs (2.0 to 3.0) were achieved in 79% (19/24; 95% CI, 62% to 95%) of the 5-mg group compared to 63% (15/24; 95% CI, 43% to 81%) of the 10-mg group.

Structured PICO

Does a 10-mg loading dose of warfarin compared to a 5-mg loading dose increase excess anticoagulation in patients requiring warfarin therapy?

Population

49 patients seen over a 5-month period with a target international normalized ratio (INR) of 2.0 to 3.0 at a tertiary care teaching hospital.

Intervention

10 mg initial loading dose of warfarin, with subsequent doses administered on the basis of dosing nomograms.

Comparator

5 mg initial loading dose of warfarin, with subsequent doses administered on the basis of dosing nomograms.

Outcome

Laboratory markers of warfarin's anticoagulant effect (INRs and levels of factors II, VII, IX, and X and protein C) measured daily for 5 days.surrogate

A 5-mg loading dose of warfarin produces less excess anticoagulation and avoids precipitous decreases in protein C compared to a 10-mg loading dose.

Cite This Study

Linda Harrison (1997) studied this question.

synapsesocial.com/papers/6a7d1ecfb62e30e3311cc5aa https://doi.org/10.7326/0003-4819-126-2-199701150-00006

Topics

Anticoagulation in AF

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Comparison of 5-mg and 10-mg Loading Doses in Initiation of Warfarin Therapy

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Topics

Comparison of 5-mg and 10-mg Loading Doses in Initiation of Warfarin Therapy

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

Topics

Also Consider