Abstract
Objective:
To identify warfarin medication-taking patterns and the relationship between adherence and international normalized ratio (INR).
Design:
Two-month, single-blind, observational cohort.
Setting:
Veterans Affairs Medical Center ambulatory care clinics.
Patients:
Twenty-three veteran outpatients followed in a nurse-managed anticoagulation clinic were enrolled by consecutive sample. Patients were excluded if they used a medication reminder device, were scheduled to have warfarin discontinued within the next 2 months, or had been receiving warfarin less than 1 month. Twenty patients were evaluable.
Intervention:
All study patients received warfarin in a vial with an electronic medication-event monitoring system (MEMS) device. Patients were not told that adherence was being monitored.
Main Outcome Measure:
Mean and preclinic warfarin adherence, dosage changes, and INR values were tabulated.
Results:
Thirty-five percent of the patients were nonadherent with warfarin therapy. Mean and preclinic warfarin adherence rates were 86% and 90%, respectively. Medication-taking behavior was underestimated in 75% of patients. Dosage changes were more common in nonadherent patients. There was not a significant correlation between INR and adherence.
Conclusions:
MEMS adherence data could have changed pharmacologic management in select patients.
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