Key result
Warfarin 3 mg shows no difference versus 5 mg in achieving therapeutic INR for VTE.
Why the study?
Asian populations require lower warfarin maintenance doses, but the optimal initiating dose for venous thromboembolism in Asians is unknown.
Does a 3 mg versus 5 mg warfarin initiating dose improve the achievement of therapeutic INR within 8 days in newly diagnosed VTE patients?
RCT (n=56)
randomized
Does a 3 mg versus 5 mg warfarin initiating dose improve the achievement of therapeutic INR within 8 days in newly diagnosed VTE patients?
Absolute Event Rate: 60.7% vs 78.6%
p-value: p=0.146
A 3 mg warfarin starting dose showed similar efficacy to a 5 mg dose for achieving therapeutic INR by day 8, though the 5 mg dose achieved target INR faster (by day 5) in VTE patients.
3 mg warfarin initiation achieves therapeutic INR by day 8 similarly to 5 mg; confirms comparable efficacy of lower starting doses in VTE.
Objectives The fact that a lower warfarin maintenance dose is required by Asian populations is well-known. Currently, the American College of Chest Physicians recommends commencing warfarin at a dose between 5 and 10 mg for venous thromboembolism (VTE). However, the optimal initiating dose in Asians is unknown. This study aimed to evaluate the efficacy of a 3 mg versus a 5 mg of warfarin initiating dose and a corresponding nomogram in patients with VTE.Methods Eligible patients were randomized to receive 3 mg or 5 mg per day warfarin for the first 2 days of treatment. The subsequent dose was adjusted according to the warfarin nomogram. The primary outcome was the number of patients who achieved an INR 2.0–3.0 within 8 days.Results Fifty-six patients were enrolled. There was no significant difference in baseline characteristics between the groups. Seventeen (60.7%) patients in the 3-mg group and 22 (78.6%) patients in the 5-mg group achieved a therapeutic INR within 8 days (p = 0.146). However, there were significantly more patients in the 5-mg group who achieved the target INR on day 5 (53.6% vs 25.0%, p = 0.029). Furthermore, VKORC1-1639G > A was associated with an increased likelihood to achieve the target INR within 5 days (OR 3.81, 95%CI 1.19–12.16, p = 0.021).Conclusions The efficacy of a 3 mg warfarin starting dose with subsequent dose adjustment was similar to that of 5 mg on day 8 after warfarin initiation. However, a 5 mg initiating dose resulted in more patients who achieved therapeutic INR on day 5.
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Suwanawiboon et al. (2022) conducted an RCT in venous thromboembolism (n=56). warfarin vs. 5 mg per day for the first 2 days was evaluated on number of patients who achieved an INR 2.0-3.0 within 8 days (p=0.146). Initiating warfarin at 3 mg versus 5 mg in VTE patients resulted in no significant difference in achieving a therapeutic INR within 8 days (60.7% vs 78.6%, p=0.146).
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