Drug interactions
Carmustine + Phenytoin
Severity: Moderate
Carmustine and Phenytoin: 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
Reduced phenytoin concentrations have been reported in patients receiving combination chemotherapy that includes nitrosoureas, which may risk breakthrough seizures. Reduced absorption of phenytoin from the gut due to chemotherapy is a proposed contributor.
What this interaction means in plain words
Carmustine and Phenytoin 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.
Carmustine belongs to Oncology; Phenytoin belongs to Central Nervous System.
Why it happens
The mechanism is not established; impaired phenytoin absorption or altered metabolism during chemotherapy has been suggested.
What to do
Monitor phenytoin serum levels and seizure activity during chemotherapy and adjust the dose accordingly.
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 Carmustine
- Carmustine + Pentostatin Contraindicated
- Carmustine + Chlorambucil Major
- Carmustine + Cimetidine Major
- Carmustine + Cyclophosphamide Major
- Carmustine + Dacarbazine Major
- Carmustine + Fingolimod Major
Frequently asked questions
Can I take Carmustine with Phenytoin?
MediHelp rates the interaction as moderate. Carmustine and Phenytoin 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. Reduced phenytoin concentrations have been reported in patients receiving combination chemotherapy that includes nitrosoureas, which may risk breakthrough seizures. Reduced absorption of phenytoin from the gut due to chemotherapy is a proposed contributor.
How serious is the interaction between Carmustine and Phenytoin?
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 serum levels and seizure activity during chemotherapy and adjust the dose accordingly.
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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