Objective: To compare the continuity of methylphenidate hydrochloride (MPH) therapy among youth Medicaid beneficiaries treated for attention-deficit/hyperactivity disorder with immediate-release (IR) or extended-release (ER) MPH formulations. Method An analysis was conducted of statewide California Medicaid claims (2000-2003) focusing on children and adolescents, ages 6 to 17 years, who started ER-MPH or IR-MPH treatment for attention-deficit/hyperactivity disorder. The study cohorts were limited to youth who had not filled a prescription for MPHs, amphetamines, pemoline, or atomoxetine for 6 months preceding the index prescription and remained eligible for Medicaid benefits for the following 12 months. The study groups were compared with respect to background demographic traits and clinical characteristics. Mean and median duration of MPH treatment episodes were defined to terminate if a gap of 30 or more days occurred from the end of the last prescription supply to the start of the next prescription. Survival time ratios were used to assess treatment duration controlling for group differences in background characteristics.
Results: As compared with patients initiating IR-MPH treatment, patients initiating ER-MPH treatment had a significantly longer mean estimated duration of treatment (ER-MPH, 140.3 days [95% confidence interval (CI), 136.3-144.4 days] vs IR-MPH, 103.4 days [95% CI, 101.3-103.4 days]). Similar results were found in analyses stratified by patient age, race/ethnicity, and sex. Controlling for group differences in age, sex, race/ethnicity, coprescribed psychotropic medications, other treated mental disorders, case management, managed care participation, and seasonal effects, ER-MPH treatment initiation was associated with an average 37% longer duration of treatment than IR-MPH treatment (survival time ratio, 1.37 [95% CI, 1.32-1.42]). Among patients treated with ER-MPH, treatment initiation with an osmotic release oral system MPH (Concerta) was associated with significantly longer mean duration (147.2 days [95% CI, 142.6-151.7 days]) than treatment initiation with Metadate CD (controlled delivery) (113.0 days [95% CI, 100.9-125.1 days]) or Ritalin LA (long acting) (101.1 days [95% CI, 91.2-111.0 days]), respectively.
Conclusions: Extended-release MPH formulations were associated with greater continuity of MPH treatment than IR formulations in the study population. Initial selection of an ER formulation may help to prolong continuity of MPH therapy among youth Medicaid beneficiaries with attention-deficit/hyperactivity disorder.