Serum
phenytoin levels can be markedly increased by azapropazone, and
toxicity can develop rapidly. A similar interaction has been seen with phenylbutazone, and it seems likely that oxyphenbutazone will interact similarly. Fosphenytoin, a prodrug of
phenytoin, may interact similarly with these
NSAIDs.
It has been suggested that the concurrent use of
phenytoin and these
NSAIDs should be avoided.