Drug interactions
Ketoconazole + Ondansetron
Severity: Moderate
Ketoconazole 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
Ketoconazole inhibits CYP3A4 and may increase ondansetron exposure, but ondansetron has several clearance routes so the effect is limited. Ketoconazole itself can prolong the QT interval, adding a pharmacodynamic concern.
What this interaction means in plain words
Ketoconazole 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.
Ketoconazole belongs to Anti Fungals; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
CYP3A4 inhibition reduces ondansetron clearance, together with additive QT prolongation.
What to do
No empirical dose change is required; check an ECG and electrolytes in patients with QT risk factors and monitor for arrhythmia symptoms.
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 Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Frequently asked questions
Can I take Ketoconazole with Ondansetron?
MediHelp rates the interaction as moderate. Ketoconazole 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. Ketoconazole inhibits CYP3A4 and may increase ondansetron exposure, but ondansetron has several clearance routes so the effect is limited. Ketoconazole itself can prolong the QT interval, adding a pharmacodynamic concern.
How serious is the interaction between Ketoconazole 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: No empirical dose change is required; check an ECG and electrolytes in patients with QT risk factors and monitor for arrhythmia symptoms.
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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