Background: Methylphenidate (MPH)-related adverse events are well characterized. Their predictors and their relationship with therapeutic effects are less well understood. Here we examine these issues in relation to two long-acting formulations.
Method: Comparison of Methylphenidates in the Analog Classroom Setting (COMACS) was made in a large (n = 184) placebo-controlled trial comparing Equasym XL/Metadate CD, Concerta, and placebo (PLA) using a Laboratory School protocol. Therapeutic effects were measured using direct observation, scores on a simple math productivity task and parent ratings. Parents also completed the Barkley Stimulant Side Effect Rating Scale (BSSERS).
Results: The BSSERS had six factors: Emotionality, sleep/appetite, disengaged, dizzy, uninterested, and aches. Treatment effects were seen only for emotionality (which improved) and sleep and appetite (which worsened). Adverse events were not predictable from personal and clinical characteristics of patients. Sleep/appetite adverse events were not associated with therapeutic effects. Improvements in attention-deficit/hyperactivity disorder (ADHD) and emotionality were correlated.
Discussion: The results support a narrow conceptualization of MPH adverse events with problems restricted to appetite and sleep. These effects were not predictable on the basis of available information and may be due to an underlying mechanism rather distinct from those determining therapeutic effects.