Drug interactions
Fluconazole + Ondansetron
Severity: Major
Fluconazole and Ondansetron: major interaction.
Last updated Sources: UK SmPC
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
Both drugs can prolong the QT interval, and fluconazole may also modestly raise ondansetron levels. Together they increase the risk of torsades de pointes, especially with electrolyte disturbances or cardiac disease.
What this interaction means in plain words
Fluconazole and Ondansetron 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.
Fluconazole belongs to Anti Fungals; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive QT prolongation, with CYP3A4 inhibition by fluconazole reducing ondansetron clearance.
What to do
Obtain a baseline ECG, correct potassium and magnesium, and use the lowest effective ondansetron dose. Consider an alternative antiemetic in patients with QT risk factors.
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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References
- Ondansetron 4 mg film-coated tablets - SmPC sections 4.3/4.5 (class statement: antifungals; "antifungals (such as ketoconazole)") — electronic medicines compendium (UK SmPC)
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 Fluconazole
- Dihydroergotamine intranasal + Fluconazole Contraindicated
- Dihydroergotamine + Fluconazole Contraindicated
- Dofetilide + Fluconazole Contraindicated
- Domperidone + Fluconazole Contraindicated
- Dronedarone + Fluconazole Contraindicated
- Erythromycin + Fluconazole Contraindicated
Frequently asked questions
Can I take Fluconazole with Ondansetron?
MediHelp rates the interaction as major. Fluconazole and Ondansetron 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. Both drugs can prolong the QT interval, and fluconazole may also modestly raise ondansetron levels. Together they increase the risk of torsades de pointes, especially with electrolyte disturbances or cardiac disease.
How serious is the interaction between Fluconazole and Ondansetron?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline ECG, correct potassium and magnesium, and use the lowest effective ondansetron dose. Consider an alternative antiemetic in patients with QT risk factors.
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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