Drug interactions
L-methylfolate + Phenytoin
Severity: Moderate
L-methylfolate and Phenytoin: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Folate supplementation has been associated with lower phenytoin concentrations and loss of seizure control in some patients. The effect is variable and probably dose related.
What this interaction means in plain words
L-methylfolate and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
L-methylfolate belongs to Miscellaneous; Phenytoin belongs to Central Nervous System.
Why it happens
The mechanism is not firmly established; increased phenytoin metabolism with folate repletion has been proposed.
What to do
Monitor phenytoin levels and seizure frequency after starting or changing L-methylfolate, and adjust the phenytoin dose if needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Other interactions of L-methylfolate
Frequently asked questions
Can I take L-methylfolate with Phenytoin?
MediHelp rates the interaction as moderate. L-methylfolate and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Folate supplementation has been associated with lower phenytoin concentrations and loss of seizure control in some patients. The effect is variable and probably dose related.
How serious is the interaction between L-methylfolate and Phenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor phenytoin levels and seizure frequency after starting or changing L-methylfolate, and adjust the phenytoin dose if needed.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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