BACKGROUND:Warfarin sodium therapy is usually initiated with a loading dose to reduce the time required to elevate the international normalized ratio (INR). Warfarin loading doses are associated with early overanticoagulation and the development of a potential hypercoagulable state; they also may not hasten achieving an INR value between 2.0 and 3.0. This study was designed to prospectively confirm our observation that a 5-mg warfarin sodium loading dose is as effective as a 10-mg loading dose in achieving a therapeutic INR for 2 consecutive days on days 3 and 4 or 4 and 5 of therapy. METHODS:Fifty-three patients initiating warfarin therapy with a target INR of 2.0 to 3.0 were randomly allocated to receive an initial dose of 5 or 10 mg of warfarin. Subsequent doses were based on dosing algorithms. The INR was measured daily for 5 days. The primary end point of the study was the proportion of patients whose INR values were between 2.0 and 3.0 on 2 consecutive daily determinations on days 3, 4, or 5 of the study and whose INR did not exceed 3.0 at any point during the study. RESULTS: Five (24%) of 21 patients in the 10-mg group and 21 (66%) of 32 patients in the 5-mg group achieved the primary end point (relative risk 2.22, 95% confidence interval 1.30-3.70 [P < .003]). A trend toward less overanticoagulation was seen in the 5-mg warfarin group. CONCLUSION: A 10-mg loading dose of warfarin is unlikely to be more effective than a 5-mg loading dose in achieving an INR of 2.0 to 3.0 by day 4 or 5 of therapy.
RCT Entities:
BACKGROUND:Warfarin sodium therapy is usually initiated with a loading dose to reduce the time required to elevate the international normalized ratio (INR). Warfarin loading doses are associated with early overanticoagulation and the development of a potential hypercoagulable state; they also may not hasten achieving an INR value between 2.0 and 3.0. This study was designed to prospectively confirm our observation that a 5-mg warfarin sodium loading dose is as effective as a 10-mg loading dose in achieving a therapeutic INR for 2 consecutive days on days 3 and 4 or 4 and 5 of therapy. METHODS: Fifty-three patients initiating warfarin therapy with a target INR of 2.0 to 3.0 were randomly allocated to receive an initial dose of 5 or 10 mg of warfarin. Subsequent doses were based on dosing algorithms. The INR was measured daily for 5 days. The primary end point of the study was the proportion of patients whose INR values were between 2.0 and 3.0 on 2 consecutive daily determinations on days 3, 4, or 5 of the study and whose INR did not exceed 3.0 at any point during the study. RESULTS: Five (24%) of 21 patients in the 10-mg group and 21 (66%) of 32 patients in the 5-mg group achieved the primary end point (relative risk 2.22, 95% confidence interval 1.30-3.70 [P < .003]). A trend toward less overanticoagulation was seen in the 5-mg warfarin group. CONCLUSION: A 10-mg loading dose of warfarin is unlikely to be more effective than a 5-mg loading dose in achieving an INR of 2.0 to 3.0 by day 4 or 5 of therapy.
Authors: Nancy L Dawson; Ivan E Porter; Dusko Klipa; William R Bamlet; Mary Ann Hedges; Michael J Maniaci; Jason Persoff; Archana Roy; Alden V Patel Journal: J Thromb Thrombolysis Date: 2012-02 Impact factor: 2.300
Authors: P Lenzini; M Wadelius; S Kimmel; J L Anderson; A L Jorgensen; M Pirmohamed; M D Caldwell; N Limdi; J K Burmester; M B Dowd; P Angchaisuksiri; A R Bass; J Chen; N Eriksson; A Rane; J D Lindh; J F Carlquist; B D Horne; G Grice; P E Milligan; C Eby; J Shin; H Kim; D Kurnik; C M Stein; G McMillin; R C Pendleton; R L Berg; P Deloukas; B F Gage Journal: Clin Pharmacol Ther Date: 2010-04-07 Impact factor: 6.875
Authors: Anne Holbrook; Sam Schulman; Daniel M Witt; Per Olav Vandvik; Jason Fish; Michael J Kovacs; Peter J Svensson; David L Veenstra; Mark Crowther; Gordon H Guyatt Journal: Chest Date: 2012-02 Impact factor: 9.410
Authors: Walter Ageno; Alexander S Gallus; Ann Wittkowsky; Mark Crowther; Elaine M Hylek; Gualtiero Palareti Journal: Chest Date: 2012-02 Impact factor: 9.410