Drug interactions
Felbamate + Phenytoin
Severity: Moderate
Felbamate 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
Felbamate increases phenytoin concentrations, which may cause toxicity. Phenytoin in turn lowers felbamate concentrations, potentially reducing its efficacy.
What this interaction means in plain words
Felbamate 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.
Felbamate belongs to Central Nervous System; Phenytoin belongs to Central Nervous System.
Why it happens
Felbamate inhibits CYP2C19/2C9 metabolism of phenytoin, while phenytoin induces felbamate metabolism.
What to do
Monitor phenytoin levels and reduce the phenytoin dose as needed when starting felbamate. Monitor felbamate response and adjust its dose.
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 Felbamate
- Felbamate + Ulipristal Major
- Amisulpride + Felbamate Moderate
- Amitriptyline + Felbamate Moderate
- Apalutamide + Felbamate Moderate
- Asenapine + Felbamate Moderate
- Bosentan + Felbamate Moderate
Frequently asked questions
Can I take Felbamate with Phenytoin?
MediHelp rates the interaction as moderate. Felbamate 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. Felbamate increases phenytoin concentrations, which may cause toxicity. Phenytoin in turn lowers felbamate concentrations, potentially reducing its efficacy.
How serious is the interaction between Felbamate 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 reduce the phenytoin dose as needed when starting felbamate. Monitor felbamate response and adjust its dose.
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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