Drug interactions
Cyclophosphamide + Phenobarbital
Severity: Moderate
Cyclophosphamide and Phenobarbital: 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
Phenobarbital induces CYP2B6, CYP2C and CYP3A4 and can increase conversion of cyclophosphamide to its active metabolites. This may raise the risk of myelosuppression and urotoxicity, with uncertain impact on efficacy.
What this interaction means in plain words
Cyclophosphamide and Phenobarbital 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.
Why it happens
Enzyme induction by phenobarbital increases cyclophosphamide bioactivation.
What to do
Monitor blood counts and for toxicity such as hemorrhagic cystitis. Prefer a non-inducing antiseizure drug where possible.
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 Cyclophosphamide
Frequently asked questions
Can I take Cyclophosphamide with Phenobarbital?
MediHelp rates the interaction as moderate. Cyclophosphamide and Phenobarbital 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. Phenobarbital induces CYP2B6, CYP2C and CYP3A4 and can increase conversion of cyclophosphamide to its active metabolites. This may raise the risk of myelosuppression and urotoxicity, with uncertain impact on efficacy.
How serious is the interaction between Cyclophosphamide and Phenobarbital?
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 blood counts and for toxicity such as hemorrhagic cystitis. Prefer a non-inducing antiseizure drug where possible.
What other medicines interact with Cyclophosphamide?
MediHelp also lists interactions of Cyclophosphamide with, for example, Adenovirus types 4 and 7 live, Belatacept, Bendamustine. The full list is on the Cyclophosphamide page.
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