Several studies have evaluated the association between individual polymorphisms and response to methylphenidate (MPH) in subjects with attention-deficit/hyperactivity disorder (ADHD). There are few replication studies for each polymorphism of interest and results are sometimes inconsistent in this field. Although data collection from multiple international sites would allow large sample sizes, this approach has been criticized for introducing sampling variability due to differences in ethnicity and methodology between studies. To examine these issues, we aggregated nine pharmacogenetic studies from four different continents and conducted a two stage analysis: a) we evaluated the role of methodological aspects in the variability of ADHD symptom improvement between studies using meta-regression analysis; b) we assessed the role of individual characteristics of the subjects in the variability of ADHD symptoms improvement using multivariate regression analysis in the same data sets. At the study level, from five evaluated factors, only the design of the study (open studies versus randomized controlled trials) was significantly associated with heterogeneity of results (p=.001). At the individual level, age (p<. 001), comorbid oppositional defiant disorder (p<.001), and pre-treatment scores (p<.001) were associated with change of ADHD scores with treatment in the final multivariate model. Our results suggest that joint analyses of pharmacogenetic studies are feasible and promising, since fixed variables, such as the site where the study was conducted, were not related to results. Nevertheless, stratified analyses according to the design of the study must be preferentially conducted and the role of individual factors such as demographic data and comorbid profile as confounders should be assessed.

As yet, stimulants remain the preferred means of treating attention-deficit/hyperactivity disorder (ADHD) pharmacologically. They are indicated when measures based on behavioural therapy or psychoeducation alone are not sufficient. How-ever, the period of effectiveness of immediate release stimulants is often not satisfactory. A variety of retarded forms of methylphenidate have now been developed and approved for the German market. This paper presents an overview of clinical studies on effectiveness, period of effectiveness and the profile of side effects of different forms stimulants available in Germany. In clinical practice, the new retard products represent effective alternatives. There is an advantage in administering this drug in a once-daily single dose. At the same time, the side effects that are caused by an extended period of effectiveness have to be studied in detail. A more precise adaptation to the daily obligations and needs of children and adolescents is needed. Possibly, a combination with unretareded MPH might lead to a better effect/side-effect profile.

Da die Aufmerksamkeitsdefizit-Hyperaktivitäts-Störung (ADHS) nicht nur eine der häufigsten psychiatrischen Störungen im Kindes-und Jugendalter ist, sondern auch bis ins Erwachsenenalter andauern kann, kommt ihrer Diagnose, die sich sehr komplex gestaltet, und Therapie eine wichtige Bedeutung zu. Neben Aufklärung, Beratung und Verhaltenstherapie kommt auch eine medikamentöse Behandlung in Frage, wofür verschiedene Substanzen in unterschiedlichen Darreichungsformen und Dosierungen zur Verfügung stehen.