• adherence;
  • attention-deficit/hyperactivity disorder (ADHD);
  • efficacy;
  • osmotic release oral system methylphenidate (OROS-MPH);
  • subtype

Aims:  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.

Methods:  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.

Results:  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.

Conclusions:  This study suggests better efficacy for the OROS-MPH among poor adherents to IR-MPH; however, its effectiveness varied across the three ADHD subtypes ( number NCT00460720).