Drug interactions
Phenytoin + Vincristine
Severity: Moderate
Phenytoin and Vincristine: 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 levels may fall during vincristine-containing chemotherapy, risking breakthrough seizures. Phenytoin also induces vincristine metabolism and may reduce its efficacy.
What this interaction means in plain words
Phenytoin and Vincristine 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; Vincristine belongs to Oncology.
Why it happens
Chemotherapy may reduce phenytoin absorption, and phenytoin induces CYP3A4, increasing vincristine clearance.
What to do
Check phenytoin levels regularly during chemotherapy and adjust the dose. Prefer a non-enzyme-inducing antiseizure drug.
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 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
Other interactions of Vincristine
- Adenovirus types 4 and 7 live + Vincristine Contraindicated
- Apalutamide + Vincristine Major
- Atazanavir + Vincristine Major
- Ceritinib + Vincristine Major
- Chloramphenicol + Vincristine Major
- Clarithromycin + Vincristine Major
Frequently asked questions
Can I take Phenytoin with Vincristine?
MediHelp rates the interaction as moderate. Phenytoin and Vincristine 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 levels may fall during vincristine-containing chemotherapy, risking breakthrough seizures. Phenytoin also induces vincristine metabolism and may reduce its efficacy.
How serious is the interaction between Phenytoin and Vincristine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check phenytoin levels regularly during chemotherapy and adjust the dose. Prefer a non-enzyme-inducing antiseizure drug.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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