Ondansetron and Paroxetine interaction

Ondansetron and Paroxetine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.

Major

Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.

What the FDA labels say

From the Ondansetron label · effective 2026-04-16

Major

S e ro t o ni n Syndrome: Serotonin syndrome has been reported with 5-HT 3 receptor antagonists alone but particularly with concomitant use of serotonergic drugs.

Warnings and precautionsby drug classView label on DailyMed
Major

Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of Ondansetron Injection and other serotonergic drugs.

Warnings and precautionsby drug classView label on DailyMed
Major

Patients should be informed of the increased risk of serotonin syndrome, especially if Ondansetron Injection is used concomitantly with other serotonergic drugs [see Drug Interactions (7.5 ), Overdosage (10) ] .

Warnings and precautionsby drug classView label on DailyMed
Major

Serotonergic Drugs Serotonin syndrome (including altered mental status, autonomic instability, and neuromuscular symptoms) has been described following the concomitant use of 5-HT 3 receptor antagonists and other serotonergic drugs, including SSRIs and SNRIs [see Warnings and Precautions (5.3) ] .

Drug interactionsby drug classView label on DailyMed
Minor

Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, fentanyl, lithium, tramadol, and intravenous methylene blue).

Warnings and precautionsby drug classView label on DailyMed

From the Paroxetine (BRISDELLE) label · effective 2025-04-28

Major

Serotonin Syndrome: BRISDELLE can cause serotonin syndrome with increased risk when co-administered with other serotonergic agents, but also when taken alone.

Warnings and precautionsby drug classView label on DailyMed
Major

If concomitant use of BRISDELLE with other serotonergic drugs (besides MAOIs) is clinically warranted, consider the increased risk of serotonin syndrome and carefully observe the patient, particularly during BRISDELLE initiation [see Contraindications ( 4.1 )

Warnings and precautionsby drug classView label on DailyMed
Moderate

The risk is increased with concomitant use of other serotonergic agents (including triptans, tricyclic antidepressants, fentanyl, tramadol, meperidine, methadone, lithium, tryptophan, buspirone, amphetamines, and St.

Warnings and precautionsby drug classView label on DailyMed

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Not medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.