Electronic medication-event monitoring revealed that 35% of patients were nonadherent with warfarin therapy (mean adherence 86%), with no significant correlation between INR and adherence.
Cohort (n=23)
Single-blind
No
What are the true warfarin adherence rates measured by electronic monitoring, and do they correlate with INR values in veteran outpatients?
Electronic monitoring of warfarin adherence reveals that nonadherence is common (35%) and often underestimated, yet does not significantly correlate with INR values.
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.
Barb J Mason (1996) conducted a cohort in Patients receiving warfarin therapy (n=23). Electronic medication-event monitoring system (MEMS) device was evaluated on Mean and preclinic warfarin adherence, dosage changes, and INR values. Electronic medication-event monitoring revealed that 35% of patients were nonadherent with warfarin therapy (mean adherence 86%), with no significant correlation between INR and adherence.