Are the risk factors listed in warfarin prescribing information associated with anticoagulation-related bleeding? A systematic literature review
University of Connecticut School of Pharmacy, Storrs, CT, USA.International Journal of Clinical Practice (Impact Factor: 2.57). 07/2011; 65(7):749-63. DOI: 10.1111/j.1742-1241.2011.02694.x
Warfarin significantly reduces thromboembolic risk, but perceptions of associated bleeding risk limit its use. The evidence supporting the association between bleeding and individual patient risks factors is unclear. This systematic review aims to determine the strength of evidence supporting an accentuated bleeding risk when patients with risk factors listed in the warfarin prescribing information are prescribed the drug. A systematic literature search of MEDLINE and Cochrane CENTRAL was conducted to identify studies reporting multivariate relationships between prespecified covariates and the risk of bleeding in patients receiving warfarin. The prespecified covariates were identified based on patient characteristics for bleeding listed in the warfarin package insert. Each covariate was evaluated for its association with specific types of bleeding. The quality of individual evaluations was rated as 'good', 'fair' or 'poor' using methods consistent with those recommended by the Agency for Healthcare Research and Quality (AHRQ). Overall strength of evidence was determined using the Grading of Recommendations Assessment, Development (GRADE) criteria and categorised as 'insufficient', 'very low', 'low', 'moderate' or 'high'. Thirty-four studies, reporting 134 multivariate evaluations of the association between a covariate and bleeding risk were identified. The majority of evaluations had a low strength of evidence for the association between covariates and bleeding and none had a high strength of evidence. Malignancy and renal insufficiency were the only two covariates that had a moderate strength of evidence for their association with major and minor bleeding respectively. The associations between covariates listed in the warfarin prescribing information and increased bleeding risk are not well supported by the medical literature.
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ABSTRACT: Bleeding is the main complication of oral anticoagulants, anti-vitamin K or new drugs such as anti-factor Xa or anti-thrombin agents. Risk factors associated with bleeding during warfarin therapy are discussed. For the new drugs no published data is available yet. Comparative frequencies of major bleeding during anticoagulation in atrial fibrillation and venous thromboembolism are shown. Beyond the intrinsic properties of the classic and new agents, patients characteristics and co-morbidities and an appropriate management of the antithrombotic therapy will be the factors associated with bleeding incidence in real life.
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ABSTRACT: BACKGROUND: Warfarin is effective in preventing thromboembolic events, but concerns exist regarding its use in patients with substance abuse. OBJECTIVE: Identify which patients with substance abuse who receive warfarin are at risk for poor outcomes. DESIGN: Retrospective cohort study. Diagnostic codes, lab values, and other factors were examined to identify risk of adverse outcomes. PATIENTS: Veterans AffaiRs Study to Improve Anticoagulation (VARIA) database of 103,897 patients receiving warfarin across 100 sites. MAIN MEASURES: Outcomes included percent time in therapeutic range (TTR), a measure of anticoagulation control, and major hemorrhagic events by ICD-9 codes. RESULTS: Nonusers had a higher mean TTR (62 %) than those abusing alcohol (53 %), drugs (50 %), or both (44 %, p
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