Phenytoin
Looking up whether you can take something with Phenytoin (Dilantin)? This page provides a focused reference for interaction-related questions.
1 supplements in this library have a recorded interaction with this medication
Dangerous combinations
Supplements recorded as risky with this medication1 listedHighest severity first
- →SupplementsChagaTheoreticalCaution
Theoretical concern that Chaga may increase phenytoin levels and risk of toxicity; clinically significant interaction is not established.
- Trade names
- Phenytoin (Dilantin)
- family
- anticonvulsants
Full write-up
What is it
Phenytoin is a neurological drug in the anticonvulsant family, also known by the brand name Dilantin. It is generally used in connection with seizure control.
This page is a focused educational reference for checking whether other medicines, supplements, or wellness products may interact with Phenytoin. It is not medical advice; anyone considering treatment or managing a medical condition should consult a clinician.
What interacts with it
The most consequential interactions are those that can lower phenytoin exposure and weaken seizure control. Dietary Fiber (Prebiotics) and Psyllium Husk may bind phenytoin in the gut and reduce absorption. St. John's Wort can increase phenytoin metabolism; stopping it may then increase phenytoin exposure. Therapeutic Vitamin B9 (Folate) and high-dose Vitamin B6 (Pyridoxine), particularly around 200 mg/day or more, can also lower concentrations. Changes involving folate may warrant monitoring of phenytoin levels and clinical response with a prescriber or pharmacist.
Several other combinations are uncertain or theoretically concerning because they may alter phenytoin metabolism or exposure. Rhodiola Rosea reduced CYP2C9 activity in a human probe study, which could increase concentrations and neurologic toxicity. Berberine, Cranberry Extract, and Milk Thistle (Silymarin) may also affect phenytoin handling, although clinically important effects are not established or remain uncertain. CBD (Cannabidiol) may have a bidirectional interaction with phenytoin, potentially changing levels of both substances. Evening Primrose Oil has a weakly supported theoretical concern related to seizure threshold.
Long-term phenytoin therapy can affect nutrient status. It may contribute to calcium-related bone effects through increased vitamin D catabolism, reduce absorption or increase loss of Vitamin B1 (Thiamine), and reduce Vitamin B2 (Riboflavin) status. It may also lower Vitamin B7 (Biotin) uptake and circulating status. The biotin concern is a possible nutrient-depletion interaction rather than a contraindication to combining the two. Anyone considering one of these supplements with phenytoin can discuss the combination and any appropriate monitoring with a healthcare professional.