National Survey of Adherence, Efficacy, and Side Effects of Methylphenidate in Children With Attention-Deficit/Hyperactivity Disorder in Taiwan

Objectives: To identify the determinants of adherence to immediate-release (IR) methylphenidate in children and adolescents with attention-deficit/hyperactivity disorder (ADHD); to examine the impact of adherence on ADHD-related symptoms; and to compare the efficacy, adherence, and side effects of IR methylphenidate and osmotic release oral system (OROS) methylphenidate.

Method: This national survey, involving 12 hospitals, consisted of 2 phases of assessment. Treatment adherence in 240 (39.5%) of the 607 children aged 5 to 16 years with a clinical diagnosis of DSM-IV ADHD enrolled in the study was poor (defined as missing >= 1 dose of ADHD medication a day and on 2 days or more during school days). Children with poor adherence at phase 1 were able to switch to OROS methylphenidate, while adherents remained on the IR variant. We reassessed 124 poor adherents who switched to OROS methylphenidate. The global ADHD severity, parent-child interaction, classroom behavior, academic performance, and side effects of the child subjects were evaluated by investigators. Parents completed the rating scales about the ADHD-related symptoms. The study began in April 2005 and was completed in February 2006.

Results: Determinants for poor adherence included older age, later onset of ADHD, family history of ADHD, higher paternal education level, and multi-dose administration. Mental retardation and treatment at medical centers were inversely related to poor adherence. Overall, poor adherence was associated with more severe ADHD-related symptoms by comparison to good adherence. Similar side effect profile, superior adherence, and improved efficacy were demonstrated in intra-individual comparison of the OROS and IR methylphenidate forms.

Conclusion: Given that poor adherence to medication may be an important reason for suboptimal outcome in ADHD treatment, physicians should ensure adherence with therapy before adjusting dosage or switching medication.