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A Better Mousetrap?
PTINR.com Staff
Improving patient adherence remains a significant challenge for chronic medications such as warfarin, which can be easily monitored.
The former Surgeon General Dr. C. Everett Koop said, "medications are only good when you take them." He may have not been behind a new study on warfarin (Coumadin ®) dosing adherence, but efforts continue to try to improve medication efficacy through improved patient compliance.
A study published in the November, 2009 issue of CHEST entitled, "Can We Predict Daily Adherence to Warfarin? Results from the IN-RANGE Study" determined if improvement in warfarin daily adherence could favorably impact time in target range and therefore patient safety. The study was supported by a grant from the National Institute of Health (NIH) and the Agency for Healthcare Research and Quality (AHRQ).
Study authors cited patient adherence to warfarin dosing is poor with one in five doses taken incorrectly – even in the setting of an anticoagulation clinic.1 Poor adherence was a contributing factor to patient risk – "even short periods of sub-therapeutic or supra-therapeutic anticoagulation may expose patients to recurrent thrombosis or dangerous side effects such as intracranial hemorrhage."1
The use of 9 demographic, clinical and psychosocial factors evaluated 114 patients in a prospective study design used an electronic prescription bottle cap to measure daily patient adherence to warfarin dosing. The study identified patients at greatest risk of poor daily compliance included the following characteristics: currently working, disabled and 55 years old or older, taking warfarin for a history of stroke or TIA, and low cognitive functioning.1
One of the studies short-comings was the lack of association between an indication of an opened pillbox and actual ingestion of warfarin. The only guarantee of compliance remains an INR test result within a timeframe relevant to warfarin’s half-life.
Home INR Testing (patient self testing) is supported by Medicare and ensures clinicians’ patients are not only opening their pillbox – they are receiving the benefit of the medication. Compliance and adherence will play an increasing role in patient outcomes as new agents are nearing U.S. approval. Compliance with chronic medications that do require monitoring or cannot be monitored, particularly for asymptomatic medications, remains a significant challenge for healthcare. While new factor Xa and fibrin inhibitors look promising in non-inferior to warfarin designed controlled clinical trials – real world outcomes remain a practical question about their long-term cost-effectiveness.
1 Anthony, M. 2009. Warfarin interactions with substances listed in drug information compendia and in the FDA-approved label for warfarin sodium. Clinical Pharmacology & Therapeutics, 1-5