Adverse response to methylphenidate in combination with valproic acid.

The use of methylphenidate (MPH) in combination with antiepileptic drugs is gaining acceptance for children with epilepsy who have the symptoms of attention-deficit hyperactivity disorder (ADHD). We report two cases of an adverse effect of dyskinesia and bruxism when MPH was given to children maintained on valproic acid. These adverse effects were rapid and severe. Because of the potential for serious and persistent side effects from this combination of medications, caution is warranted in the treatment of ADHD with MPH for children taking valproic acid. Further prospective studies of the use of valproic acid and MPH in combination are required.