Better efficacy for the osmotic release oral system methylphenidate among poor adherents to immediate‐release methylphenidate in the three ADHD subtypes

<jats:p><jats:bold>Aims: </jats:bold> To determine factors for switching to osmotic release oral system methylphenidate (OROS‐MPH) among poor adherents to immediate‐release methylphenidate (IR‐MPH); and to compare the efficacy of OROS‐MPH on the three attention‐deficit/hyperactivity disorder (ADHD) subtypes in a multi‐site prospective observational study in Taiwan.</jats:p><jats:p><jats:bold>Methods: </jats:bold> The sample included 240 children with ADHD, aged 6–16 years, who were poor adherents to IR‐MPH, 137 of whom were switched to OROS‐MPH. The child psychiatrists diagnosed the Diagnostic Statistical Manual of Mental Disorders (4th edition) ADHD subtypes and assessed the medical history, adherence, side‐effects, global ADHD severity, and family/school effectiveness. Parents reported their child's behavioral symptoms.</jats:p><jats:p><jats:bold>Results: </jats:bold> The determinants for an OROS‐MPH switch were higher dosage, shorter treatment and thrice‐daily administration of IR‐MPH, and more severe inattention symptoms. Hyperactivity and oppositional symptoms were greater in the ADHD combined and hyperactive‐impulsive subtypes than the inattentive subtype. Switching to OROS‐MPH significantly improved behavioral symptoms and family/school measures, and this was most evident in the ADHD‐combined group, followed by the ADHD‐inattentive group. Inattention influenced not only academic performance, but also overall classroom behaviors and the parent–child relationship, with the latter two also influenced by oppositional symptoms.</jats:p><jats:p><jats:bold>Conclusions: </jats:bold> This study suggests better efficacy for the OROS‐MPH among poor adherents to IR‐MPH; however, its effectiveness varied across the three ADHD subtypes (ClinicalTrials.gov number NCT00460720).</jats:p>