Drug interactions
Fosphenytoin + Ziprasidone
Severity: Moderate
Fosphenytoin 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
Fosphenytoin is converted to phenytoin, an inducer of CYP3A4, which may lower ziprasidone levels and reduce antipsychotic effect. Carbamazepine, a related inducer, reduced ziprasidone exposure by about a third.
What this interaction means in plain words
Fosphenytoin 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.
Fosphenytoin belongs to Central Nervous System; Ziprasidone belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 by phenytoin increasing ziprasidone clearance.
What to do
Monitor psychiatric response and consider increasing the ziprasidone dose if effect is lost. Reassess the dose if the anticonvulsant 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 Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Ziprasidone?
MediHelp rates the interaction as moderate. Fosphenytoin 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. Fosphenytoin is converted to phenytoin, an inducer of CYP3A4, which may lower ziprasidone levels and reduce antipsychotic effect. Carbamazepine, a related inducer, reduced ziprasidone exposure by about a third.
How serious is the interaction between Fosphenytoin 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 psychiatric response and consider increasing the ziprasidone dose if effect is lost. Reassess the dose if the anticonvulsant 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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