MajorAntineoplastic, pyrimidine analogue (5-FU)×Antiepileptic, hydantoin derivative (sodium channel blocker)
Updated · Methodology
Mechanism
5-FU inhibits CYP2C9 – phenytoin rises 2-fold. Toxicity with ataxia, nystagmus.
Symptoms
Nystagmus, ataxia, drowsiness after 7-14 days.
Management
Check phenytoin level on day 7. Reduce dose 25-50%.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- AEMPS: Ficha tecnica de Fluorouracilo (5-FU) (2023)– AEMPS CIMA, 2023