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