Drug interactions
Omeprazole + Phenytoin
Severity: Moderate
Omeprazole 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
Omeprazole can reduce phenytoin clearance and raise its levels, with possible toxicity such as nystagmus, ataxia and confusion. Phenytoin may also induce omeprazole metabolism and lessen acid suppression.
What this interaction means in plain words
Omeprazole 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.
Omeprazole belongs to Gastrointestinal Tract; Phenytoin belongs to Central Nervous System.
Why it happens
Omeprazole inhibits CYP2C19/CYP2C9 metabolism of phenytoin, while phenytoin induces CYP enzymes that clear omeprazole.
What to do
Monitor serum phenytoin concentrations and clinical signs of toxicity when starting or stopping omeprazole, adjusting phenytoin as needed. Check for adequate acid suppression.
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 Omeprazole
- Mavacamten + Omeprazole Contraindicated
- Omeprazole + Rilpivirine Contraindicated
- Acalabrutinib + Omeprazole Major
- Atazanavir + Omeprazole Major
- Citalopram + Omeprazole Major
- Clopidogrel + Omeprazole 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 Omeprazole with Phenytoin?
MediHelp rates the interaction as moderate. Omeprazole 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. Omeprazole can reduce phenytoin clearance and raise its levels, with possible toxicity such as nystagmus, ataxia and confusion. Phenytoin may also induce omeprazole metabolism and lessen acid suppression.
How serious is the interaction between Omeprazole 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 serum phenytoin concentrations and clinical signs of toxicity when starting or stopping omeprazole, adjusting phenytoin as needed. Check for adequate acid suppression.
What other medicines interact with Omeprazole?
MediHelp also lists interactions of Omeprazole with, for example, Mavacamten, Rilpivirine, Acalabrutinib. The full list is on the Omeprazole page.
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