Minor
Suspected
説明
Ranitidine may slightly increase phenytoin bioavailability through modest inhibition of CYP2C9, though the interaction is less significant than with cimetidine.
機序
Ranitidine inhibits CYP2C9 weakly, reducing phenytoin hydroxylation; additionally, raised gastric pH from H2 blockade may alter phenytoin absorption kinetics.
臨床的意義
Case reports describe phenytoin toxicity (nystagmus, ataxia) with ranitidine; the effect is variable and generally smaller than cimetidine's.
対処法
Monitor phenytoin levels and watch for signs of toxicity when starting ranitidine; consider switching to a less interacting agent if needed.