Drug interactions
Cyclophosphamide + Primidone
Severity: Moderate
Cyclophosphamide and Primidone: 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
Primidone is metabolized to phenobarbital, an enzyme inducer, which can increase conversion of cyclophosphamide to active metabolites. This may increase toxicity such as myelosuppression and urotoxicity.
What this interaction means in plain words
Cyclophosphamide and Primidone 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.
Cyclophosphamide belongs to Oncology; Primidone belongs to Central Nervous System.
Why it happens
Enzyme induction (CYP2B6, CYP3A4) by primidone and its metabolite 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
Other interactions of Primidone
- Lorlatinib + Primidone Contraindicated
- Lurasidone + Primidone Contraindicated
- Primidone + Ranolazine Contraindicated
- Primidone + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
- Primidone + Voriconazole Contraindicated
- Abiraterone + Primidone Major
Frequently asked questions
Can I take Cyclophosphamide with Primidone?
MediHelp rates the interaction as moderate. Cyclophosphamide and Primidone 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. Primidone is metabolized to phenobarbital, an enzyme inducer, which can increase conversion of cyclophosphamide to active metabolites. This may increase toxicity such as myelosuppression and urotoxicity.
How serious is the interaction between Cyclophosphamide and Primidone?
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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