Raised
serum phenytoin levels and
phenytoin toxicity have been seen in 3 patients also given methylphenidate, but it is an uncommon reaction and two studies suggest that most patients do not experience an interaction.
This interaction is unlikely to be generally significant, but bear it in mind in case of an unexpected response to treatment. Indicators of
phenytoin toxicity include blurred vision, nystagmus, ataxia or drowsiness.