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Anticoagulation Control with Daily Low‐Dose Vitamin K to Reduce Clinically Adverse Outcomes and International Normalized Ratio Variability: A Systematic Review and Meta‐Analysis
Author(s) -
Lam Jason,
Schulman Sam,
Witt Daniel M.,
Vandvik Per Olav,
Qayyum Fareeha,
Holbrook Anne M.
Publication year - 2013
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1002/phar.1302
Subject(s) - medicine , vitamin k antagonist , adverse effect , warfarin , randomized controlled trial , placebo , relative risk , meta analysis , confidence interval , cochrane library , medline , clinical trial , intensive care medicine , atrial fibrillation , alternative medicine , pathology , political science , law
Study Objectives Difficulties managing warfarin therapy have led to speculation that daily supplementation with a low dose of vitamin K might improve anticoagulation control and clinical outcomes. Thus we sought to review the available medical literature systematically examining the effectiveness of low‐dose vitamin K supplementation for the reduction of clinically relevant adverse events due to vitamin K antagonist ( VKA ) use and for stabilization of the international normalized ratio ( INR ). Design We searched the Medline and Embase databases, the C ochrane Library, I nternational P harmaceutical A bstracts, and the U.S. National Institutes of Health clinical trials registry for randomized controlled trials of vitamin K supplementation versus placebo in patients receiving a VKA . We evaluated the outcomes of hemorrhage, thromboembolic events, and percentage of time in therapeutic range ( TTR ) of INR s by using the Grading of Recommendations Assessment, Development and Evaluation system for rating quality of evidence in the abstracted studies. Setting All randomized controlled trials studies published between 1970 and August 2012 which fitted our search strategy. Patients Patients over the age of 18 years on VKA therapy. Results Of the 624 studies we identified and screened, three studies (626 patients) were included in the meta‐analysis. Most of the patients had a satisfactory TTR at baseline. We found low‐quality evidence—downgraded for imprecision and risk of bias (i.e., limitation in study design and/or execution)—of no effect of vitamin K use (100 to 200 μg) on hemorrhagic events (relative risk [ RR ] 3.2, 95% confidence interval [ CI] 0.2–64.2) and thromboembolic events ( RR 2.2, 95% CI 0.1–47.5) and a significant but clinically unimportant effect on TTR with an absolute increase of 3.5% (95% CI 1.1–6.0). Conclusion This meta‐analysis, despite the few studies and overall low quality, suggests no beneficial role of low‐dose (100 to 200 μg) vitamin K supplementation on the reduction of clinically relevant adverse events in patients taking VKA s, despite a small improvement of the TTR . Data were insufficient, however, from patients with unstable INR s.