Drug interactions
Olaparib + Phenytoin
Severity: Major
Olaparib and Phenytoin: 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 markedly decreases olaparib exposure, potentially reducing efficacy of PARP inhibitor therapy.
What this interaction means in plain words
Olaparib and Phenytoin 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.
Olaparib belongs to Oncology; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing olaparib clearance.
What to do
Avoid coadministration and use a non-inducing anticonvulsant.
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 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 Olaparib
- Amiodarone + Olaparib Major
- Amobarbital + Olaparib Major
- Apalutamide + Olaparib Major
- Aprepitant + Olaparib Major
- Azathioprine + Olaparib Major
- Carbamazepine + Olaparib Major
Frequently asked questions
Can I take Olaparib with Phenytoin?
MediHelp rates the interaction as major. Olaparib and Phenytoin 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 markedly decreases olaparib exposure, potentially reducing efficacy of PARP inhibitor therapy.
How serious is the interaction between Olaparib and Phenytoin?
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 coadministration and use a non-inducing anticonvulsant.
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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