Clonazepam and Phenytoin Interaction
Drug interaction information between Clonazepam and Phenytoin.
Clonazepam and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Clonazepam 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
Phenytoin makes your body clear clonazepam faster, and clonazepam can also change the amount of phenytoin in your system.
FDA Label Information
Clonazepam has the potential to influence concentrations of phenytoin. Monitoring of phenytoin concentration is recommended when clonazepam is co-administrated with phenytoin. Cytochrome P450 inducers, such as phenytoin, carbamazepine, lamotrigine, and phenobarbital induce clonazepam metabolism, causing an approximately 38% decrease in plasma clonazepam levels.
Clonazepam Also Interacts With
- Sertraline major
- Fluoxetine major
- Felbamate major
- Diazepam moderate
- Lamotrigine 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 Clonazepam + 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 Clonazepam's 14. In the minor band specifically: Clonazepam has 10 (also Lamotrigine, Fluconazole, Carbamazepine, Ranitidine); Phenytoin has 120 (also Atorvastatin, Omeprazole, Simvastatin, Methylphenidate).
What mechanism field is on file for Clonazepam and Phenytoin?
Phenytoin makes your body clear clonazepam faster, and clonazepam can also change the amount of phenytoin in your system.
Phenytoin carries more major-labeled pairs than Clonazepam
SPL source-record counts only. This page's band is minor · classes on file: Clonazepam (Benzodiazepine); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Clonazepam's 3. This page itself is in the minor band, not the major band.
3 major · 1 moderate · 10 minor · 14 total
- Other minor peers for Clonazepam
- Lamotrigine
- Fluconazole
- Carbamazepine
- Ranitidine
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.