Drug interactions
Phenytoin + Ziprasidone
Severity: Moderate
Phenytoin and Ziprasidone: 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 is an inducer of CYP3A4 and may lower ziprasidone concentrations, potentially reducing antipsychotic effect. The related inducer carbamazepine reduces ziprasidone exposure by roughly a third, so a similar though uncertain effect may occur.
What this interaction means in plain words
Phenytoin and Ziprasidone 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 belongs to Central Nervous System; Ziprasidone belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 by phenytoin accelerates ziprasidone metabolism.
What to do
Monitor for reduced antipsychotic response and consider increasing the ziprasidone dose if needed. Reassess the dose if phenytoin is stopped.
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 Ziprasidone
- Amiodarone + Ziprasidone Contraindicated
- Amitriptyline + Ziprasidone Contraindicated
- Arsenic trioxide + Ziprasidone Contraindicated
- Bedaquiline + Ziprasidone Contraindicated
- Chloroquine + Ziprasidone Contraindicated
- Citalopram + Ziprasidone Contraindicated
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 Ziprasidone?
MediHelp rates the interaction as moderate. Phenytoin and Ziprasidone 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 is an inducer of CYP3A4 and may lower ziprasidone concentrations, potentially reducing antipsychotic effect. The related inducer carbamazepine reduces ziprasidone exposure by roughly a third, so a similar though uncertain effect may occur.
How serious is the interaction between Phenytoin and Ziprasidone?
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 antipsychotic response and consider increasing the ziprasidone dose if needed. Reassess the dose if phenytoin is stopped.
What other medicines interact with Ziprasidone?
MediHelp also lists interactions of Ziprasidone with, for example, Amiodarone, Amitriptyline, Arsenic trioxide. The full list is on the Ziprasidone page.
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