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. Trial Registration: clinicaltrials.gov Identifier NCT00460720