Oxcarbazepine and Phenytoin Interaction
Drug interaction information between Oxcarbazepine and Phenytoin.
Oxcarbazepine and Phenytoin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Oxcarbazepine 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
Oxcarbazepine can slow down how your body gets rid of phenytoin, which may cause phenytoin to build up to high levels.
FDA Label Information
7 DRUG INTERACTIONS • Phenytoin: Increased phenytoin levels. Reduced dose of phenytoin may be required ( 7.1 ) • Carbamazepine, Phenytoin, and Phenobarbital: Decreased plasma levels of MHD (the active metabolite). Dose adjustments may be necessary ( 7.1 ) • Oral Contraceptive: Oxcarbazepine may decrease the effectiveness of hormonal contraceptives ( 7.3 ) 7.1 Effect of Oxcarbazepine on Other Drugs Phenytoin levels have been shown to increase with concomitant use of oxcarbazepine at doses greater than 1200 mg/day [see Clinical Pharmacology ( 12.3 )].
Oxcarbazepine Also Interacts With
- Dolutegravir/Lamivudine moderate
- Tranylcypromine moderate
- Rifampin minor
- Phenobarbital minor
- Bictegravir/Emtricitabine/Tenofovir 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 Oxcarbazepine + 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 Oxcarbazepine's 18. In the minor band specifically: Oxcarbazepine has 16 (also Rifampin, Phenobarbital, Bictegravir, Carbamazepine); Phenytoin has 120 (also Atorvastatin, Omeprazole, Simvastatin, Methylphenidate).
What mechanism field is on file for Oxcarbazepine and Phenytoin?
Oxcarbazepine can slow down how your body gets rid of phenytoin, which may cause phenytoin to build up to high levels.
Phenytoin carries more major-labeled pairs than Oxcarbazepine
SPL source-record counts only. This page's band is minor · classes on file: Oxcarbazepine (Anticonvulsant); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Oxcarbazepine's 0. This page itself is in the minor band, not the major band.
0 major · 2 moderate · 16 minor · 18 total
- Other minor peers for Oxcarbazepine
- Rifampin
- Phenobarbital
- Bictegravir
- Carbamazepine
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.