PHENYTOIN AND TRIMETHOPRIM
Phenytoin serum levels can be raised by co-trimoxazole (which contains trimetho- prim). Trimethoprim can increase decrease the clearance of phenytoin by 30% and prolong its half-life. Phenytoin toxicity may develop in some cases. Fosphenytoin, a prodrug of phenytoin, may interact similarly.
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.
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.