Treatment outcomes with methylphenidate formulations among patients with ADHD: retrospective claims analysis of a managed care population

Abstract

Describe treatment patterns, resource use, and predictors of methylphenidate (MPH) switch among children (6-12 years), adolescents (13-17 years), and adults (≥ 18 years) with attention-deficit/hyperactivity disorder (ADHD). This retrospective U.S. managed care database study used medical, pharmacy, and enrollment data to examine treatment patterns among patients with ≥ 1 ADHD diagnosis code (ICD-9 314.00-314.9), MPH pharmacy claims during 01/01/2004-09/30/2006, and no ADHD pharmacy claims in prior 6 months. Patients were followed for 1 year for dosage change, switch (change to non-MPH treatment), augmentation, persistence (number days on index medication) and adherence (days supplied/days persistent). End points were assessed by age group and MPH formulation. Cox proportional hazards modeling was conducted to determine predictors of MPH switch. Among 23,860 MPH users, 51.4% had a dosing change, 14% switched to a non-MPH agent, and 4% augmented MPH therapy. Among those prescribed long-acting (LA) MPH (N = 14,681), switching rates were 14% for children, 13% for adolescents, and 16% for adults. Augmentation rates for LA MPH were <5%. Overall, 53% of patients were adherent with mean persistence of 219 days. For the subgroup of patients prescribed LA MPH (n = 14,681), adherence ranged from 49% (adolescents) to 59% (children); persistence varied between 183 days (adults) to 256 days (children). During the 1-year follow-up, office/clinic visits were the major driver of health care resource use in MPH patients (mean 9.7 visits/patient). Patients with psychiatric comorbidity utilized significantly greater services. Predictors of MPH switch included psychiatric comorbidity (hazards ratio [HR] 1.37; 95% confidence interval [CI] = 1.26-1.48; p < 0.0001) and specialty prescribers (HR 1.19, 95% CI = 1.04-1.35; p = 0.011). Potential limitations of this study include use of claims data for definition of drug usage; inclusion of medications approved for use in ADHD; assessment of switching that may not have captured short-term augmentation; absence of economic, clinical and other variables from the claims dataset that may have influenced treatment selection, and outcomes. The 6-month baseline period to determine newly treated patients may not guarantee exclusion of all previously treated patients who restart therapy after an extended period. Children exhibited the highest persistence of MPH users. ADHD patients on MPH therapy with a psychiatric comorbidity may require additional follow-up to help improve adherence and reduce health care resource use.