Acetaminophen And Codeine and Palonosetron: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jun 30, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acetaminophen And Codeine
Palonosetron
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Your pain medicine contains codeine, and palonosetron is an anti-nausea drug often given around chemotherapy or surgery. Both can gently raise a brain chemical called serotonin. When two serotonin-affecting drugs are combined, there is a small, mostly theoretical chance of a reaction called serotonin syndrome.
Signs to watch for include feeling agitated or restless, a fast heartbeat, sweating, shivering, muscle twitching or stiffness, or a fever. This is uncommon, and your care team can manage it. Keep taking both exactly as prescribed, and let your doctor or pharmacist know right away if you feel any of these symptoms, especially soon after starting or changing a dose.
Effect: Additive serotonergic activity from codeine (an opioid with weak serotonergic properties) combined with palonosetron (a 5-HT3 receptor antagonist) may increase the risk of serotonin syndrome.
- Mechanism: Pharmacodynamic, additive serotonergic effects (not a CYP or transporter interaction).
- Direction/magnitude: Additive PD risk; magnitude not quantified.
- Onset: Unspecified; highest concern at initiation and dose changes.
- Evidence: Theoretical.
- Management: Monitor for hyperthermia, autonomic instability, neuromuscular hyperactivity (clonus, rigidity), and altered mental status. Discontinue codeine if serotonin syndrome is suspected.
What happens
Increased risk of serotonin syndrome
Interaction Deep Dive
Serotonin syndrome has occurred when opioids like codeine are taken together with serotonergic agents. When such combined use cannot be avoided, monitor the patient closely, especially when therapy is being started or doses are being modified. Should serotonin syndrome be suspected, stop codeine123.
Why it happens (mechanism)
Additive serotonergic effects
How to manage this interaction
This combination can usually be used safely with attention. Here is how it is typically handled:
- Keep taking both as prescribed unless your care team tells you otherwise.
- Your team may watch you more closely, especially when starting either drug or adjusting a dose.
- Report symptoms promptly: agitation, confusion, fast heartbeat, sweating, shivering, muscle twitching or stiffness, or fever.
If serotonin syndrome is suspected, your prescriber may stop the codeine. Ask your pharmacist or doctor about any concerns and about which symptoms to watch for.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
Common questions
Can I take Acetaminophen And Codeine and Palonosetron together?
Combining codeine with palonosetron carries a small, theoretical risk of serotonin syndrome; keep taking both as prescribed but watch for agitation, fast heartbeat, sweating, shivering, or muscle twitching, and get help right away if they appear. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Palonosetron interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Acetaminophen And Codeine and Palonosetron interaction managed?
This combination can usually be used safely with attention. Here is how it is typically handled: Keep taking both as prescribed unless your care team tells you otherwise. Your team may watch you more closely, especially when starting either drug or adjusting a dose. Report symptoms promptly: agitation, confusion, fast heartbeat, sweating, shivering, muscle twitching or stiffness, or fever. If sero… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Acetaminophen And Codeine or Palonosetron need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (3)
- Product Information: Codeine sulfate oral tablets, codeine sulfate oral tablets. West-Ward Pharmaceuticals Corp (per DailyMed), Eatontown, NJ, 2016. DailyMed
- Product Information: Codeine sulfate oral solution, codeine sulfate oral solution. Hikma Pharmaceuticals USA Inc(per FDA), Berkeley Heights, NJ, 2023. DailyMed
- Product Information: Codeine sulfate oral tablets, codeine sulfate oral tablets. Hikma Pharmaceuticals USA Inc. (per FDA), Berkeley Heights, NJ, 2023. DailyMed
Keep reading about Acetaminophen And Codeine
Keep reading about Palonosetron
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