There is some
in vitro evidence to indicate that
modafinil may possibly inhibit the
metabolism of
phenytoin. Fosphenytoin, a prodrug of
phenytoin, may interact similarly.
It may be prudent to monitor the effects of
phenytoin in the presence of
modafinil, taking levels if any evidence of
toxicity occurs (e.g. blurred vision, nystagmus, ataxia or drowsiness).