A case report describes
phenytoin toxicity in a boy given
allopurinol. Another study
found raised
phenytoin levels in 2 of 18 patients given allopurino.
The
clinical importance of this interaction is probably small, but bear it in mind in case of an unexpected response to treatment. Indicators of
phenytoin toxicity include blurred vision, nystagmus, ataxia or drowsiness.