Drug interactions
Doxorubicin + Fosphenytoin
Severity: Moderate
Doxorubicin and Fosphenytoin: 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, a CYP3A4 and P-gp inducer that may lower doxorubicin exposure and reduce antitumor effect. Cytotoxic chemotherapy can also lower phenytoin concentrations, risking loss of seizure control.
What this interaction means in plain words
Doxorubicin and Fosphenytoin 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.
Doxorubicin belongs to Oncology; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and drug transporters, while chemotherapy-related effects (reduced absorption, altered protein binding/metabolism) may change phenytoin levels.
What to do
Monitor phenytoin concentrations (free levels if albumin is low) and seizure control during chemotherapy and adjust the dose. Consider a non-enzyme-inducing anticonvulsant such as levetiracetam where feasible.
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 Doxorubicin
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 Doxorubicin with Fosphenytoin?
MediHelp rates the interaction as moderate. Doxorubicin and Fosphenytoin 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, a CYP3A4 and P-gp inducer that may lower doxorubicin exposure and reduce antitumor effect. Cytotoxic chemotherapy can also lower phenytoin concentrations, risking loss of seizure control.
How serious is the interaction between Doxorubicin and Fosphenytoin?
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 phenytoin concentrations (free levels if albumin is low) and seizure control during chemotherapy and adjust the dose. Consider a non-enzyme-inducing anticonvulsant such as levetiracetam where feasible.
What other medicines interact with Doxorubicin?
MediHelp also lists interactions of Doxorubicin with, for example, Adenovirus types 4 and 7 live, Belatacept, Cobicistat. The full list is on the Doxorubicin page.
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