Short-term side effects of stimulant medication are increased in preschool children with attention-deficit/hyperactivity disorder: a double-blind placebo-controlled study.

Preschool children with attention-deficit/hyperactivity disorder (ADHD) (27 boys, 5 girls, mean age 4 years 10 months) participated in a double-blind placebo-controlled crossover drug study to assess the side effects of methylphenidate. Children received twice daily, for at least 1 week each, placebo, 0.3 mg/kg methylphenidate, and 0.5 mg/kg methylphenidate. Side effects were monitored by a parent rating scale designed for medication studies. In general, methylphenidate was tolerated relatively well, with no children withdrawing because of adverse effects. Of 17 childhood behaviors usually associated with side effects, 8 behaviors showed significant changes, generally at the higher dose of methylphenidate. Interestingly, 3 of the side effects were associated with improved behavior. The number of side effects appeared higher than what is usually reported in a population of school-age children, but few parents reported them as being severe. Severe side effects were reported in less than 10% of the sample, with approximately as many reports of severe effects on placebo as on low and high doses of the medication. The results indicate that methylphenidate has a relatively low toxicity in preschool children (over the first 7-10 days), that some behavioral changes that might be viewed as side effects of methylphenidate are actually normal behaviors or ADHD behaviors in preschool children (e.g., sociability), that these "side-effect" behaviors are more common in preschool than school-age children, that some "side effects" of methylphenidate are associated with improvements in behavior, and that preschool and school-age children may have different side effects of methylphenidate (e.g., mood changes and anxiety).