Anticoagulation: Effect of a Warfarin Adherence Aid on Anticoagulation Control in an Inner-City Anticoagulation Clinic Population

BACKGROUND: Poor adherence to warfarin therapy is a major contributor to subtherapeutic anticoagulation. OBJECTIVE: To determine whether use of a monthly medication organizer, filled at each clinic visit, improves anticoagulation control among warfarin-treated patients. METHODS: Patients who had a history of nonadherence to warfarin and were attending an inner-city anticoagulation clinic were enrolled in this prospective cohort study and provided with a 28-day medication organizer. Patients were instructed to bring their organizers and warfarin tablets to each anticoagulation clinic visit over the following 3 months. At each visit, the international normalized ratio (INR) was measured, warfarin adherence was assessed, and the organizer was filled with the prescribed warfarin regimen until the next scheduled visit. Data on warfarin adherence and INR values during the 3 months prior to enrollment were collected from medical records and compared with postenrollment data. RESULTS: Thirteen patients were enrolled and completed at least one postenrollment clinic visit. Adherence to warfarin therapy improved with use of the medication organizer (mean +/- SD preenrollment 55 +/- 25%, postenrollment 67 +/- 21%; p = 0.06). There was a significant decrease in the proportion of subtherapeutic INR values (60 +/- 25% to 35 +/- 29%; p = 0.04) and a significant improvement in the percent of time spent within the therapeutic INR range (32 +/- 22% to 56 +/- 28%; p = 0.03) after enrollment. CONCLUSIONS: Use of a monthly medication organizer significantly reduced the percent of subtherapeutic INR values and improved the time spent within the therapeutic anticoagulation range among previously nonadherent patients managed in an inner-city anticoagulation clinic.