Electronic measurement of compliance with mercaptopurine in pediatric patients with acute lymphoblastic leukemia

Twenty-four pediatric patients with acute lymphoblastic leukemia (ALL) on maintenance therapy were evaluated for their compliance with taking their prescribed doses of oral mercaptopurine (6-MP). Procedure and Results. We utilized the Medication Event Monitoring System (MEMS; Aprex Corporation, Fremont, CA) for the study. Compliance was defined as the number of days doses were taken as a percentage of the total number of days doses were prescribed during the study period. The mean age of the patients was 7.3 years (range 2.6-17.2 (years). Patients were evaluated for a mean of 44 days (range 15-94 days). Thirty-three percent of patients (8) took less than 90% and 17% (4) took less than 80% of their prescribed pills. Eight patients were also evaluated for a difference in compli-ance between morning and evening administration. For the comparison of compliance between a morning vs. an evening schedule a trend toward improved compliance in the evening was found. Five patients had an increase and one patient a decrease in compliance with an evening schedule (differences ranged from 0.2% to 51.3%), with two patients having 100% compliance on both schedules. Conclusions. Our data raise concern that a significant proportion of pediatric patients are non-compliant with pill taking and demonstrate that the timing of administration of 6-MP in children with ALL may be crucial in some patients and supports the hypothesis that evening administration of 6-MP is associated with a lower risk of relapse.