Drug interactions
Phenytoin + Pyridoxine
Severity: Moderate
Phenytoin and Pyridoxine: 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
High doses of pyridoxine have been reported to lower serum phenytoin concentrations, potentially reducing seizure control. The effect is mainly seen with large doses.
What this interaction means in plain words
Phenytoin and Pyridoxine 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.
Why it happens
High-dose pyridoxine may increase hepatic metabolism of phenytoin; the mechanism is not fully established.
What to do
Avoid high-dose pyridoxine supplementation, or monitor serum phenytoin levels and seizure frequency if it is required.
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
Frequently asked questions
Can I take Phenytoin with Pyridoxine?
MediHelp rates the interaction as moderate. Phenytoin and Pyridoxine 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. High doses of pyridoxine have been reported to lower serum phenytoin concentrations, potentially reducing seizure control. The effect is mainly seen with large doses.
How serious is the interaction between Phenytoin and Pyridoxine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid high-dose pyridoxine supplementation, or monitor serum phenytoin levels and seizure frequency if it is required.
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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