Phenytoin serum levels can be raised by
co-trimoxazole.
Phenytoin toxicity may
develop in some cases.
The risk of
toxicity is small and is most likely in those with
serum phenytoin levels at the top end of the range. Monitor
phenytoin levels and adjust the dose accordingly. Indicators of
phenytoin toxicity include blurred vision, nystagmus, ataxia or drowsiness.