Adherence to medication for attention deficit/hyperactivity disorder: does time frame matter?

Objectives  Attention deficit/hyperactivity disorder (ADHD) medication users frequently take ‘drug holidays’ during the summer months. The study objective was to compare ADHD medication adherence for the school year (SY, 270 days) and for the entire year (EY, 365 days) by medication type, medication class and duration of action. Methods  Continuously enrolled Texas Medicaid children (≤18 years) who had two or more prescription claims for an ADHD medication served as the study population. SY (1 September–31 May) and EY (1 January–31 December) prescription claims were extracted from July 2002 to December 2008. Key findings  Overall mean (±SD) adherence for SY (n = 50 842) and EY (n = 62 789) time frames was 62.2% (±26.2%) and 49.8% (±30.3%), respectively. The overall frequency of patients who were adherent (medication possession ratio, ≥80%) was higher during SY (28.3%) than during EY (22.1%). Regarding medication type, mean adherence for immediate-release stimulants (52.8 versus 37.2%), extended-release stimulants (63.7 versus 52.1%), pro-drug stimulants (63.5 versus 47.6%) and non-stimulants (62.9 versus 52.5%) was higher during SY than EY, respectively. Regarding medication class, mean adherence for stimulants (62.1 versus 49.4%) and non-stimulants (62.9 versus 52.5%) was higher during SY than EY. Similarly, regarding duration of action, mean adherence for short-acting agents (52.2 versus 37.2%) and long-acting agents (63.4 versus 52.2%) was higher during SY than EY, respectively. Conclusions  Patients were more adherent during the SY compared to the EY. Due to unique patient medication-taking behaviors, ADHD medication adherence differs depending on the time frame used.