Drug interactions
Ondansetron + Paroxetine
Severity: Moderate
Ondansetron and Paroxetine: 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
Ondansetron is a 5-HT3 antagonist that has been linked in reports to serotonin syndrome when given with serotonergic antidepressants such as paroxetine. The risk is considered low but the syndrome may involve agitation, tremor, hyperreflexia, hyperthermia and autonomic instability.
What this interaction means in plain words
Ondansetron and Paroxetine 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.
Ondansetron belongs to Gastrointestinal Tract; Paroxetine belongs to Central Nervous System.
Why it happens
Possible additive serotonergic effects; the pharmacodynamic mechanism for 5-HT3 antagonists is not firmly established.
What to do
Counsel patients and monitor for signs of serotonin toxicity after starting or increasing ondansetron. Stop ondansetron and treat supportively if symptoms appear.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Ondansetron and Paroxetine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
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 Paroxetine
- Isocarboxazid + Paroxetine Contraindicated
- Methylene blue + Paroxetine Contraindicated
- Paroxetine + Phenelzine Contraindicated
- Paroxetine + Pimozide Contraindicated
- Paroxetine + Procarbazine Contraindicated
- Paroxetine + Selegiline Contraindicated
Frequently asked questions
Can I take Ondansetron with Paroxetine?
MediHelp rates the interaction as moderate. Ondansetron and Paroxetine 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. Ondansetron is a 5-HT3 antagonist that has been linked in reports to serotonin syndrome when given with serotonergic antidepressants such as paroxetine. The risk is considered low but the syndrome may involve agitation, tremor, hyperreflexia, hyperthermia and autonomic instability.
How serious is the interaction between Ondansetron and Paroxetine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Counsel patients and monitor for signs of serotonin toxicity after starting or increasing ondansetron. Stop ondansetron and treat supportively if symptoms appear.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
