What the label lists and what reports show
Palonosetron side effects
Palonosetron's FDA label: “Most common adverse reactions in chemotherapy-induced nausea and vomiting in adults (≥5%) are: headache and constipation ( 6.1 ) postoperative nausea and vomiting (≥ 2%) are: QT prolongation, bradycardia, headache, and constipation” FAERS holds 5,254 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is diarrhoea (367 reports).
- Generic listed
- A presentation discontinued
Check it at the source: the palonosetron FDA label on DailyMed (effective April 29, 2025, Avyxa Pharma, LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of POSFREA?POSFREA may cause serious side effects, including: ● Serious allergic reactions, such as anaphylaxis. Get emergency medical help right away if you get any of the following symptoms. ○ hives ○ swollen face ○ breathing trouble ○ chest pain ● Serotonin Syndrome. A possible life threatening problem called serotonin syndrome can happen with medicines called 5-HT 3 receptor antagonists, including POSFREA, especially when used with medicines used to treat depression and migraine headaches called serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs) and certain other medicines. […]
Source: FDA drug label, Avyxa Pharma, LLC, effective April 29, 2025 (SPL set 13a201ba-c86d-48c5-a0e1-a3e0b4e6a2a7), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions in chemotherapy-induced nausea and vomiting in adults (≥5%) are: headache and constipation ( 6.1 ) postoperative nausea and vomiting (≥ 2%) are: QT prolongation, bradycardia, headache, and constipation
Table 2: Common Adverse Reactions* in Adults with Receiving MEC (Studies 1 and 2) or HEC (Study 3)
| Adverse Reaction | Palonosetron 0.25 mg intravenously (N=633) | Ondansetron 32 mg intravenously (N=410) | Dolasetron 100 mg intravenously (N=194) |
|---|---|---|---|
| Headache | 9% | 8% | 16% |
| Constipation | 5% | 2% | 6% |
| Diarrhea | 1% | 2% | 2% |
| Dizziness | 1% | 2% | 2% |
| Fatigue | < 1% | 1% | 2% |
| Abdominal Pain | < 1% | < 1% | 2% |
| Insomnia | < 1% | 1% | 2% |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedSerious or otherwise clinically significant adverse reactions reported in other sections of labeling: Hypersensitivity Reactions [see Warnings and Precautions (5.1) ] Serotonin Syndrome [see Warnings and Precautions (5.2) ] Most common adverse reactions in chemotherapy-induced nausea and vomiting in adults (≥5%) are: headache and constipation ( 6.1 ) postoperative nausea and vomiting (≥ 2%) are: QT prolongation, bradycardia, headache, and constipation ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Avyxa Pharma, LLC at 1-888-520-0954 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatc h. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of POSFREA has been established from adequate and well-controlled studies of another intravenous formulation of palonosetron [see Clinical Studies (14) ]. Below is a display of the adverse reactions of palonosetron in these adequate and well-controlled studies. …
Source: FDA drug label, Avyxa Pharma, LLC, effective April 29, 2025 (SPL set 13a201ba-c86d-48c5-a0e1-a3e0b4e6a2a7), via openFDA; the full label on DailyMed
What do FAERS reports show?
5,254 reports list palonosetron among the medicines taken, each a report of something that happened, not proof the medicine caused it; 897 are coded as a death and 2,710 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 7 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Palonosetron: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions