Drug interactions
Citalopram + Ondansetron
Severity: Major
Citalopram and Ondansetron: major interaction.
Last updated Sources: US FDA label
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 prolong the QT interval, and citalopram does so in a dose-dependent way, increasing arrhythmia risk when combined. Both also have serotonergic activity, so serotonin syndrome is a theoretical additional concern.
What this interaction means in plain words
Citalopram 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.
Citalopram belongs to Central Nervous System; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive QT prolongation, plus possible additive serotonergic effects (5-HT3 antagonism with serotonin reuptake inhibition).
What to do
Avoid the combination when possible; if used, keep citalopram at or below labeled dose limits and monitor the ECG and electrolytes. Watch for agitation, tremor, hyperreflexia and fever.
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
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 Citalopram
- Cisapride + Citalopram Contraindicated
- Citalopram + Dronedarone Contraindicated
- Citalopram + Escitalopram Contraindicated
- Citalopram + Isocarboxazid Contraindicated
- Citalopram + Methylene blue Contraindicated
- Citalopram + Phenelzine Contraindicated
Frequently asked questions
Can I take Citalopram with Ondansetron?
MediHelp rates the interaction as major. Citalopram 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 prolong the QT interval, and citalopram does so in a dose-dependent way, increasing arrhythmia risk when combined. Both also have serotonergic activity, so serotonin syndrome is a theoretical additional concern.
How serious is the interaction between Citalopram 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: Avoid the combination when possible; if used, keep citalopram at or below labeled dose limits and monitor the ECG and electrolytes. Watch for agitation, tremor, hyperreflexia and fever.
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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