CNS Drugs

, Volume 25, Issue 2, pp 157–169

Efficacy of Methylphenidate for Adults with Attention-Deficit Hyperactivity Disorder

A Meta-Regression Analysis
  • Xavier Castells
  • Josep Antoni Ramos-Quiroga
  • David Rigau
  • Rosa Bosch
  • Mariana Nogueira
  • Xavier Vidal
  • Miguel Casas
Original Research Article

DOI: 10.2165/11539440-000000000-00000

Cite this article as:
Castells, X., Ramos-Quiroga, J.A., Rigau, D. et al. CNS Drugs (2011) 25: 157. doi:10.2165/11539440-000000000-00000

Abstract

Background: The efficacy of methylphenidate for adults with attention-deficit hyperactivity disorder (ADHD) shows wide between-study variability, which yields heterogeneous results in meta-analysis. The reasons for this variability have not been comprehensively investigated.

Objectives: To determine the influence of treatment-related covariates of methylphenidate for adults with ADHD by means of meta-analysis. Clinical and methodological moderators and clinical trial reporting quality were also collected to control for their potential confounding effect.

Methods: We searched for randomized, placebo-controlled clinical trials investigating the efficacy of methylphenidate for adults with ADHD. The study outcome was the efficacy of methylphenidate for reducing ADHD symptom severity. Treatment-related covariates included dose, type of drug-release formulation (formulations with a continuous drug release vs those with a non-continuous drug release), dose regimen (fixed vs flexible) and treatment length. Clinical (presence of co-morbid substance use disorders [SUD]) and methodological (design and rater) covariates were also collected, in addition to clinical trial reporting quality. The standardized mean difference (SMD) was calculated for each study. The analysis of the influence of methylphenidate effect modifiers was performed by means of random-effects meta-regression.

Results: Eighteen studies were included. Dose, type of formulation and SUD appeared to modify the efficacy of methylphenidate in the bivariate analysis. These variables were included in a multivariate meta-regression, which showed that methylphenidate, at an average dose of 57.4 mg/day, delivered by means of non-continuous-release formulations, had a moderate effect on ADHD symptoms compared with placebo (SMD 0.57–0.58). A dose-response relationship was found, indicating that efficacy could be increased by SMD 0.11–0.12 for every 10 mg increment of methylphenidate. Continuous-release formulations and co-morbid SUD appeared to reduce the efficacy of methylphenidate. Nevertheless, the effect of treatment formulation may have been confounded by co-morbid SUD, since all studies using this continuous-release formulation were conducted in dual ADHD-SUD patients. No residual heterogeneity was found.

Conclusions: This study shows that methylphenidate improves ADHD symptoms in adults in a dose-dependent fashion. The efficacy of methylphenidate appears to be reduced in patients with co-morbid SUD. It is unclear whether methylphenidate efficacy is influenced by the type of formulation, because the effect of this covariate is confounded by that of co-morbid SUD.

Supplementary material

40263_2012_25020157_MOESM1_ESM.pdf (48 kb)
Supplementary material, approximately 49 KB.

Copyright information

© Adis Data Information BV 2011

Authors and Affiliations

  • Xavier Castells
    • 1
    • 2
  • Josep Antoni Ramos-Quiroga
    • 1
    • 3
  • David Rigau
    • 4
  • Rosa Bosch
    • 1
  • Mariana Nogueira
    • 1
  • Xavier Vidal
    • 5
  • Miguel Casas
    • 1
    • 3
  1. 1.Psychiatry DepartmentHospital Universitari Vall d’HebronBarcelonaSpain
  2. 2.Unit of Clinical Pharmacology, Department of Medical Sciences, School of MedicineUniversitat de GironaGironaSpain
  3. 3.Psychiatry DepartmentUniversitat Autònoma de BarcelonaBarcelonaSpain
  4. 4.Iberoamerican Cochrane CenterBarcelonaSpain
  5. 5.Department of Pharmacology, Therapeutics and ToxicologyUniversitat Autònoma de BarcelonaBarcelonaSpain