Seasonal Patterns of Medications for Treating Attention-Deficit/Hyperactivity Disorder: Comparison of Methylphenidate and Atomoxetine

Abstract

Purpose: Medication is a first-line effective treatment for attention-deficit/hyperactivity disorder (ADHD). Currently, immediate-release methylphenidate (IR-MPH), the osmotic, controlled-release formulation of methylphenidate (OROS-MPH), and atomoxetine (ATX) are the only 3 medications approved in Taiwan for the treatment of ADHD. Short-term discontinuation of ADHD treatment is often seen among patients undergoing drug therapy. The goal of this study was to evaluate potential seasonal patterns in ADHD prescriptions and compare the seasonal changes of IR-MPH, OROS-MPH, and ATX use.

Methods: Taiwan's National Health Insurance database was used to gather information on patients diagnosed with ADHD (N = 145,269) from January 2000 to December 2011. The monthly data regarding person-days and receipt of treatment with IR-MPH, OROS-MPH, and ATX were analyzed. Time series analyses and autoregressive integrated moving average models were used to examine the seasonal patterns in person-days receiving ADHD pharmacotherapy. A general linear model with a post hoc test was used to determine the differences in monthly consumption of ADHD medications.

Findings: This study comprised 145,269 patients (mean age: 7.7 years; 78.6% were boys) diagnosed with ADHD. The prescriptions of IR-MPH (seasonal autoregressive: estimate [SE], 0.92 [0.04], t = 22.87, P < 0.001) and OROS-MPH (estimate [SE], 0.84 [0.09], t = 9.41, P < 0.001) both showed significant seasonal patterns, but ATX prescriptions did not (estimate [SE], 0.50 [0.55]; t = 0.90; P = 0.373). IR-MPH and OROS-MPH prescriptions shared similar seasonal trends. The mean person-days of consumption in July were lower than in other months, with the exception of February and August. Meanwhile, for ATX, the person-days of consumption in February were the lowest. The mean person-days in February were significantly lower than in March and May but did not differ from those in other months.

Implications: The seasonal patterns of IR-MPH and OROS-MPH use coincide with school holidays. These findings suggest that discontinuing a drug during the holiday period may be popular for people undergoing ADHD pharmacotherapy, especially with regard to methylphenidate prescriptions. However, additional research is necessary to determine whether temporary discontinuation of drug therapy is related to patient outcomes.

Keywords: ADHD; drug adherence; epidemiology; pharmacotherapy; stimulant.