Version July 2025
| Drugs that increase the metabolism of phenytoin and decrease total and unbound plasma concentrations include: |
| Folic acid |
| Dexamethasone |
| Phenobarbital |
| Diazepam |
| Rifampin |
| Methadone |
| Nitrofurantoin |
| Estrogens |
| Drugs that decrease phenytoin metabolism and increase plasma concentrations include: |
| Valproic acid |
| Carbamazepine |
| Warfarin |
| Isoniazid |
| Cimetidine, ranitidine |
| Omeprazole |
| Ibuprofen |
| Metronidazole |
| Chloramphenicol |
| Fluconazole |
| Fluoxetine |
| Risperidone |
| Amiodarone |
| Allopurinol |
