• The Number of Chromosomal Aberrations Per 100 Cells Excluding Gaps at Baseline and at the End of Treatment i.e Day 84 (Week 12) [ Time Frame: baseline and at end of treatment (Week 12) ] [ Designated as safety issue: Yes ]
  The number of chromosomal aberrations per 100 cells excluding gaps at Baseline (n=33, n=32) and at Week 12 (n=33, n=32) was counted in blood samples cultured for 48 hours using a standard protocol. The types of abnormalities included translocations (reciprocal and non-reciprocal), insertions, dicentrics, fragments, inversions, chromatid exchanges (quadriradials and triradials), breaks, and other unusual observations, eg, aneuploidy, tetraploidy or endoreduplication.
  
  
• The Number of Micronuclei Per 1000 Binucleated Cells Endpoints at Baseline and at the End of Treatment i.e Day 84 (Week 12) [ Time Frame: baseline and at end of treatment (Week 12) ] [ Designated as safety issue: Yes ]
  The number of micronuclei per 1000 binucleated cells was measured at Baseline ( n=34 , n=29 ) and at the end of treatment, Week 12 (n =34, n= 29), in blood cultured for 48 hours using a standard protocol.
  
  

• Number of Sister Chromatoid Exchanges Per Cell [ Time Frame: baseline and at end of treatment (Week 12) ] [ Designated as safety issue: Yes ]
  Blood collected at baseline (n=20, n=14) and at the end of treatment, Week 12, (n= 20, n= 14) was cultured for 48 hours using a standard protocol. Giemsa staining and/or fluorescent in situ hybridization (FISH) chromosome painting was done on the cells in metaphase and the number of chromatoid exchanges per cell was recorded by blinded raters.
  
  
• Pharmacokinetic/Pharmacodynamic Relationship of Methylphenidate Blood Levels and Cytogenetic Changes [ Time Frame: End of treatment (Week 12) ] [ Designated as safety issue: No ]
  Since no cytogenetic effects were observed, blood samples were not analyzed for pharmacokinetics/pharmacodynamics.
  
  
• Change From Baseline to End of Treatment (Week 12) on the Conners' ADHD/DSM-IV Scale for Parents (CADS-P) [ Time Frame: Baseline to end of treatment (Week 12) ] [ Designated as safety issue: No ]
  Parents completed the Conners' ADHD/DSM-IV Scale for Parents (CADS-P) consisting of the ADHD Index (12 items) and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)( 18 items). Parents rated their child's behavior of the previous week from a list of common problems. When asked "How much of a problem has this been in the last week?" parents selected 0 = none, not at all, seldom, or very infrequently; 3 = very much true, or it occurs very often or frequently; or 1 or 2 for ratings in between. A score of 50 is considered normal and more than 70 markedly atypical.
  
  
• Change From Baseline to the End of Treatment (Week 12) on the Global Improvement Rating of the Clinical Global Impression Scale (CGI-I) [ Time Frame: From baseline to the end of treatment (Week 12) ] [ Designated as safety issue: No ]
  The Clinical Global Impression scale (CGI-I) is a clinician-rated instrument designed to assess the overall change of illness relative to baseline. The CGI-I consists of 7 ratings as follows: 1 = very much improved, 2 = much improved, 3 = minimally improved, 4 = no change, 5 = minimally worse, 6 = much worse, and 7 = very much worse. CGI-I assessments are relative to the patient's status at the Baseline visit.
  
  
• Change From Baseline to the End of Treatment (Week 12) on the Severity of Illness Rating of the Clinical Global Impression Scale (CGI-S) [ Time Frame: From baseline to the end of treatment (Week 12) ] [ Designated as safety issue: No ]
  The Clinical Global Impression scale (CGI-S) is a clinician-rated instrument designed to assess the severity of illness. The CGI-S rating indicates illness severity at each time-point on a scale as follows: 1 = normal, not at all ill; 2 = borderline mentally ill; 3 = mildly ill; 4 = moderately ill; 5 = markedly ill; 6 = severely ill; and 7 = extremely ill. CGI-S assessments are relative to the patient's status at the Baseline visit.
  
  

This study will determine whether the administration of extended-release methylphenidate in treatment-naïve children with Attention Deficit Hyperactivity Disorder (ADHD) affects the frequency of chromosomal abnormalities.