Effect of OROS methylphenidate on encopresis in children with attention-deficit/hyperactivity disorder

Although encopresis shows a high rate of comorbidity in patients with attention-deficit/hyperactivity disorder (ADHD), the etiologic origin of this relationship and the effect of ADHD drugs on encopresis are unclear. In this chart review, we explored the effect of OROS long-acting methylphenidate (MPH) treatment on encopresis in children with ADHD. We also evaluated the relationship between the clinical variables of ADHD and encopresis.

The sample consisted of 21 children and adolescents (20 boys and 1 girl) with encopresis and coexisting ADHD 7-15 years of age. Their clinical characteristics and baseline (visit 1) and end of the second months' (visit 2) Conners' Parent Rating Scale (CPRS) subscores were recorded. Retrospective clinician determinations were made using the Clinical Global Impressions-Severity subscale (CGI-S) for encopresis severity and the Clinical Global Impressions-Improvement subscale (CGI-I) for encopresis response.

According to the CGI-I, 14 subjects (71.4 %) showed much or very much improvement in their encopresis at the second visit. All of the CPRS scores showed a significant reduction during the second visit. No association was found between the CGI-I score and the changes in any of the CPRS scores. Baseline oppositional defiant disorder (ODD) and conduct disorder (CD) scores were correlated with the CGI-S score; however, no association was found between core ADHD symptom severity and the CGI-S score. With regard to the encopresis outcome, the baseline CD score was negatively correlated with the CGI-I score, and the baseline ODD score was prone to show a negative correlation with the CGI-I score.

These results suggest that coexisting behavioral problems may be a vulnerability factor based on the severity of encopresis, and that MPH treatment may have a positive effect on encopresis in children and adolescents with ADHD.