Drug interactions
Phenytoin + Risperidone
Severity: Moderate
Phenytoin and Risperidone: 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 enzyme inducer and can lower plasma levels of risperidone and its active metabolite. This may reduce antipsychotic efficacy and lead to relapse of psychotic symptoms.
What this interaction means in plain words
Phenytoin and Risperidone 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; Risperidone belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 (and likely P-glycoprotein) by phenytoin increases the clearance of risperidone and 9-hydroxyrisperidone.
What to do
Monitor clinical response and increase the risperidone dose if needed. Reduce the dose again 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 Risperidone
- Ibutilide + Risperidone Contraindicated
- Risperidone + Vandetanib Contraindicated
- Adagrasib + Risperidone Major
- Amiodarone + Risperidone Major
- Amisulpride + Risperidone Major
- Amoxapine + Risperidone 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 Phenytoin with Risperidone?
MediHelp rates the interaction as moderate. Phenytoin and Risperidone 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 enzyme inducer and can lower plasma levels of risperidone and its active metabolite. This may reduce antipsychotic efficacy and lead to relapse of psychotic symptoms.
How serious is the interaction between Phenytoin and Risperidone?
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 clinical response and increase the risperidone dose if needed. Reduce the dose again if phenytoin is stopped.
What other medicines interact with Risperidone?
MediHelp also lists interactions of Risperidone with, for example, Ibutilide, Vandetanib, Adagrasib. The full list is on the Risperidone page.
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