Drug interactions
Phenytoin + Thiotepa
Severity: Major
Phenytoin and Thiotepa: major 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 induces CYP3A4 and may change thiotepa metabolism and the balance between parent drug and active metabolite. This may alter efficacy or toxicity.
What this interaction means in plain words
Phenytoin and Thiotepa can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Phenytoin belongs to Central Nervous System; Thiotepa belongs to Oncology.
Why it happens
CYP3A4 induction by phenytoin alters thiotepa metabolism.
What to do
Avoid concurrent use and consider a non-inducing anticonvulsant such as levetiracetam. If unavoidable, monitor closely for adverse reactions and response.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Thiotepa
- Bendamustine + Thiotepa Major
- Chlorambucil + Thiotepa Major
- Clarithromycin + Thiotepa Major
- Cyclophosphamide + Thiotepa Major
- Dacarbazine + Thiotepa Major
- Deferiprone + Thiotepa Major
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
Frequently asked questions
Can I take Phenytoin with Thiotepa?
MediHelp rates the interaction as major. Phenytoin and Thiotepa can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Phenytoin induces CYP3A4 and may change thiotepa metabolism and the balance between parent drug and active metabolite. This may alter efficacy or toxicity.
How serious is the interaction between Phenytoin and Thiotepa?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid concurrent use and consider a non-inducing anticonvulsant such as levetiracetam. If unavoidable, monitor closely for adverse reactions and response.
What other medicines interact with Thiotepa?
MediHelp also lists interactions of Thiotepa with, for example, Bendamustine, Chlorambucil, Clarithromycin. The full list is on the Thiotepa page.
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