Diazepam and Phenytoin Interaction
Drug interaction information between Diazepam and Phenytoin.
Diazepam and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Diazepam and Phenytoin. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Diazepam makes it harder for your body to get rid of phenytoin. This can cause the level of phenytoin in your blood to rise.
FDA Label Information
Phenytoin There have also been reports that the metabolic elimination of phenytoin is decreased by diazepam.
Diazepam Also Interacts With
- Clonazepam moderate
- Fluoxetine moderate
- Mirtazapine moderate
- Raloxifene moderate
- Omeprazole minor
Phenytoin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Posaconazole major
- Ranolazine major
- Voriconazole major
- Apixaban moderate
Frequently Asked Questions
What SPL severity band is on file for Diazepam + Phenytoin?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Phenytoin has 147 labeled pairs on file vs Diazepam's 26. In the minor band specifically: Diazepam has 22 (also Omeprazole, Ketoconazole, Fluvoxamine, Cimetidine); Phenytoin has 120 (also Atorvastatin, Omeprazole, Simvastatin, Methylphenidate).
What mechanism field is on file for Diazepam and Phenytoin?
Diazepam makes it harder for your body to get rid of phenytoin. This can cause the level of phenytoin in your blood to rise.
Phenytoin carries more major-labeled pairs than Diazepam
SPL source-record counts only. This page's band is minor · classes on file: Diazepam (Benzodiazepine); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Diazepam's 0. This page itself is in the minor band, not the major band.
0 major · 4 moderate · 22 minor · 26 total
- Other minor peers for Diazepam
- Omeprazole
- Ketoconazole
- Fluvoxamine
- Cimetidine
4 major · 23 moderate · 120 minor · 147 total
- Other minor peers for Phenytoin
- Atorvastatin
- Omeprazole
- Simvastatin
- Methylphenidate
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.