Drug interactions
Lansoprazole + Phenytoin
Severity: Moderate
Lansoprazole 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
Phenytoin induces CYP2C19 and CYP3A4 and may lower lansoprazole levels. In addition, PPIs may raise phenytoin concentrations through CYP2C19 inhibition, which is relevant for a narrow therapeutic index drug.
What this interaction means in plain words
Lansoprazole 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.
Lansoprazole belongs to Gastrointestinal Tract; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP2C19 and CYP3A4 metabolism of lansoprazole.
What to do
Monitor for reduced acid suppression and increase the lansoprazole dose if needed. Check phenytoin levels when starting or stopping the PPI.
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 Lansoprazole
- Lansoprazole + Mavacamten Contraindicated
- Lansoprazole + Rilpivirine Contraindicated
- Acalabrutinib + Lansoprazole Major
- Atazanavir + Lansoprazole Major
- Dacomitinib + Lansoprazole Major
- Dasatinib + Lansoprazole Major
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 Lansoprazole with Phenytoin?
MediHelp rates the interaction as moderate. Lansoprazole 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. Phenytoin induces CYP2C19 and CYP3A4 and may lower lansoprazole levels. In addition, PPIs may raise phenytoin concentrations through CYP2C19 inhibition, which is relevant for a narrow therapeutic index drug.
How serious is the interaction between Lansoprazole 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 for reduced acid suppression and increase the lansoprazole dose if needed. Check phenytoin levels when starting or stopping the PPI.
What other medicines interact with Lansoprazole?
MediHelp also lists interactions of Lansoprazole with, for example, Mavacamten, Rilpivirine, Acalabrutinib. The full list is on the Lansoprazole page.
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