ADHD medication use, adherence, persistence and cost among Texas Medicaid children.

OBJECTIVES: (1) Describe ADHD medication use, adherence and persistence. (2) Determine factors (e.g., medication type, demographics, concomitant medication use) associated with ADHD medication adherence and persistence. (3) Compare ADHD medication costs.
METHODS: Continuously enrolled Texas Medicaid children (3-18 years) with ≥ 2 ADHD prescription claims (July 2002-December 2008) were included. Prescription claims were grouped by medication type (i.e., immediate-release, extended-release, prodrug, non-stimulant); medication class (i.e., stimulant, non-stimulant); and duration of action (i.e., long-acting, short-acting). Adherence, using medication possession ratio, was measured continuously and dichotomously (80% cut-off). Persistence was days of continuous therapy without a 30-day gap and medication costs were reimbursement amount paid to dispensing pharmacies.
RESULTS: The study sample (n = 62,789) was primarily 6-12 years (61.7%) and male (69.2%). The majority of the subjects were prescribed extended-release agents (70.3%), stimulant agents (86.4%), and long-acting agents (84.5%). Adherence and persistence (adherence mean ± SD; adherence dichotomous; persistence mean ± SD) varied among medication type and was highest for non-stimulants (52.5 ± 30.9; 25.8%; 153.3 ± 124.3), followed by extended-release stimulants (52.1 ± 30.2; 24.1%; 143.7 ± 120.8), prodrug stimulants (47.6 ± 30.9; 21.1%; 113.3 ± 100.5) and immediate-release stimulants (37.2 ± 27.1; 9.8%; 95.4 ± 92.6). Logistic regression showed immediate-release stimulant users were 67% less adherent than non-stimulant users (p < 0.0001) and linear regression showed immediate-release, extended-release and long-acting users (p < 0.0001) were significantly less persistent than non-stimulant users. Females, increase in total number of medications, and comorbid medications were associated with better adherence and persistence. Non-stimulant agents ($4.04 ± $2.15) had the highest mean medication cost per patient per day and immediate-release stimulants had the lowest ($1.24 ± $0.97).
CONCLUSIONS: ADHD medication adherence and persistence was suboptimal. Although there was no difference in adherence between long-acting stimulant and non-stimulant users, non-stimulant users were more persistent compared to stimulant users. This study was limited due to the use of retrospective prescription claims data, which cannot capture actual patient use patterns, ICD-9 diagnoses, family history and support, or side effect profiles. Because ADHD can be effectively treated with pharmacotherapy, providers should be proactive in identifying patients with poor adherence and intervene to address barriers to medication adherence and persistence.