Drug interactions
Mifepristone + Ondansetron
Severity: Moderate
Mifepristone and Ondansetron: 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
Mifepristone inhibits CYP3A4, one of several enzymes metabolizing ondansetron, so ondansetron exposure may rise modestly. Mifepristone itself has QT-prolonging potential at higher doses, which may add to ondansetron's QT effect.
What this interaction means in plain words
Mifepristone and Ondansetron 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.
Mifepristone belongs to Endocrine; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
CYP3A4 inhibition by mifepristone reduces ondansetron clearance, with possible additive QT prolongation.
What to do
Use the lowest effective ondansetron dose and consider an ECG if there are other QT risk factors. Short single-dose use for termination of pregnancy generally needs no adjustment.
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 Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron Major
Other interactions of Mifepristone
- Apixaban + Mifepristone Contraindicated
- Argatroban + Mifepristone Contraindicated
- Cisapride + Mifepristone Contraindicated
- Cortisone + Mifepristone Contraindicated
- Cyclosporin + Mifepristone Contraindicated
- Dabigatran etexilate + Mifepristone Contraindicated
Frequently asked questions
Can I take Mifepristone with Ondansetron?
MediHelp rates the interaction as moderate. Mifepristone and Ondansetron 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. Mifepristone inhibits CYP3A4, one of several enzymes metabolizing ondansetron, so ondansetron exposure may rise modestly. Mifepristone itself has QT-prolonging potential at higher doses, which may add to ondansetron's QT effect.
How serious is the interaction between Mifepristone and Ondansetron?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the lowest effective ondansetron dose and consider an ECG if there are other QT risk factors. Short single-dose use for termination of pregnancy generally needs no adjustment.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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