Disulfiram and Phenytoin Interaction
Drug interaction information between Disulfiram and Phenytoin.
Disulfiram and Phenytoin have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Disulfiram 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
Disulfiram interferes with how your body processes phenytoin, which can cause the phenytoin to build up to toxic levels.
FDA Label Information
DISULFIRAM SHOULD BE USED WITH CAUTION IN THOSE PATIENTS RECEIVING PHENYTOIN AND ITS CONGENERS, SINCE THE CONCOMITANT ADMINISTRATION OF THESE TWO DRUGS CAN LEAD TO PHENYTOIN INTOXICATION. PRIOR TO ADMINISTERING DISULFIRAM TO A PATIENT ON PHENYTOIN THERAPY, A BASELINE PHENYTOIN SERUM LEVEL SHOULD BE OBTAINED. SUBSEQUENT TO INITIATION OF DISULFIRAM THERAPY, SERUM LEVELS OF PHENYTOIN SHOULD BE DETERMINED ON DIFFERENT DAYS FOR EVIDENCE OF AN INCREASE OR FOR A CONTINUING RISE IN LEVELS.
Disulfiram Also Interacts With
- Acamprosate minor
- Amitriptyline minor
- Metronidazole minor
- Nabilone minor
- Naltrexone 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 Disulfiram + Phenytoin?
Compiled FDA labeling labels this pair moderate. 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 Disulfiram's 8. In the moderate band specifically: Disulfiram has 1; Phenytoin has 23 (also Apixaban, Aprepitant, Canagliflozin, Carbidopa/Levodopa).
What mechanism field is on file for Disulfiram and Phenytoin?
Disulfiram interferes with how your body processes phenytoin, which can cause the phenytoin to build up to toxic levels.
Phenytoin carries more major-labeled pairs than Disulfiram
SPL source-record counts only. This page's band is moderate · classes on file: Disulfiram (Aldehyde Dehydrogenase Inhibitor); Phenytoin (Anticonvulsant (Hydantoin)).
Phenytoin has 4 major-labeled pairs vs Disulfiram's 0. This page itself is in the moderate band, not the major band.
0 major · 1 moderate · 7 minor · 8 total
Disulfiram has no other moderate-band peer in this dataset besides Phenytoin.
4 major · 23 moderate · 120 minor · 147 total
- Other moderate peers for Phenytoin
- Apixaban
- Aprepitant
- Canagliflozin
- Carbidopa/Levodopa
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.