Patient Reported Receipt of Medication Instructions for Warfarin is Associated with Reduced Risk of Serious Bleeding Events
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Adverse drug events are an important cause of preventable hospitalizations.
To identify whether patient report of receipt of medication instructions and markers of complex care (multiple physicians, recent hospitalization) predict the risk of serious bleeding for older adults on warfarin.
Prospective cohort study of older adults.
Subjects filled new or refill prescriptions for warfarin at the time of enrollment.
Hospitalizations were identified through a state-wide registry. Discharge summaries of hospitalizations for possible warfarin related bleeding events were reviewed by trained abstractors and clinical experts. Incidence rate ratios (IRR) were estimated based on person-months of exposure using Poisson regression models.
From March 2002 through May 2003, we enrolled a total of 2346 adults on warfarin. Over a two-year follow-up period, there were 126 hospitalizations due to warfarin-related bleeding (4.6 hospitalizations per 100 person-years of exposure). Patients who reported receiving medication instructions from either a physician or nurse plus a pharmacist had a 60% reduced rate of subsequently experiencing a serious bleeding event over the next 2 years (adjusted IRR 0.40, 95% CI 0.24–0.68). Having ≥4 physicians providing medication prescriptions over the last 3 months and filling prescriptions at >1 pharmacy over the last 3 months were independently associated with increased bleeding rates (adjusted IRRs 2.37, 95% CI 1.22–4.57 and 1.61, 95% CI 0.97–2.67, respectively).
The rate of warfarin-related hospitalization for bleeding is substantially lower for patients who report receiving medication instructions from a physician or nurse and a pharmacist.
KEY WORDSanticoagulation patient communication medication safety
This study was supported by grant P01-HS11530 from the Agency for Healthcare Research and Quality. The funding agency had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. Portions of this research were presented, in abstract form, at the 22nd International Conference on Pharmacoepidemiology & Therapeutic Risk Management, Lisbon, Portugal (August, 2006), and the Annual Meeting of the Society of General Internal Medicine, Toronto, CA (April, 2007).
We gratefully acknowledge the support of Tom Snedden and Terry Brown from the PACE program as well as the staff at FIRST Health, which provides administrative support for the PACE program. In addition, we thank the research staff at the University of Pennsylvania directed by Research Coordinator Jennifer Holmes.
Dr. Hennessy has received research funding from Pfizer, Inc and Shire. Dr. Kimmel has received research funding from multiple pharmaceutical manufacturers and has served as a consultant to Bayer, Pfizer, and GlaxoSmithKline, and has received honorarium from AstraZeneca. Dr. Feldman has received research funding from Amgen and Roche. Dr. Strom has received research funding from multiple pharmaceutical manufacturers and has served as a consultant to Bristol Myers Squibb. None of the other authors have any conflicts of interest or financial disclosures to declare and none of the authors has received funding from pharmaceutical manufacturers related to warfarin.
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