Acetaminophen And Codeine and Fenoldopam: 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
Fenoldopam
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.
If you take a product that has acetaminophen with codeine for pain along with fenoldopam (a blood pressure medicine usually given in the hospital), the acetaminophen part can cause a little more fenoldopam to build up in your blood. That is because both drugs use the same body pathway to be broken down, and they end up competing for it.
The good news is this is a minor, mostly theoretical concern, and no clear problems were seen with short-term use. Because fenoldopam lowers blood pressure, your care team would simply keep an eye on things like your blood pressure and heart rate. This is very manageable, so keep taking both as prescribed and let your team know how you feel.
Effect: Increased fenoldopam exposure via competition for inorganic sulfate needed for sulfation of both agents (acetaminophen is the contributor here; neither is a relevant prodrug for this pathway).
- Direction/magnitude: Cmax up ~30% (acute) to ~70% (chronic); AUC up ~50% (acute) to ~66% (chronic), with reduced metabolite levels.
- Onset: Delayed. Evidence: Theoretical. Severity: Minor; no adverse effects noted acutely.
- Management: Monitor for fenoldopam-related effects (hypotension, reflex tachycardia). Dose may be individualized by the care team if needed.
What happens
Increased fenoldopam concentration
Interaction Deep Dive
Concomitant oral administration of acetaminophen 1 g every eight hours and fenoldopam 100 mg has been associated with increases in peak serum fenoldopam concentrations of 30% (acutely) to 70% (chronically), increases in AUCs of fenoldopam of 50% (acutely) to 66% (chronically), and reductions in levels and AUCs of its metabolites. With acute use, no clinical adverse effects were noted1.
Why it happens (mechanism)
Competition for inorganic sulfate substrate needed for sulfation of both drugs
How to manage this interaction
This is a minor, theoretical interaction, so it is usually managed with simple monitoring rather than avoiding either drug.
- Keep taking both medications exactly as prescribed unless your care team tells you otherwise.
- Because fenoldopam lowers blood pressure, your team may check your blood pressure and heart rate more closely and watch for symptoms like dizziness or a fast heartbeat.
- Your fenoldopam dose may be adjusted and individualized by your care team if needed.
Ask your pharmacist or doctor if you have questions or notice new symptoms.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Fenoldopam together?
Acetaminophen can modestly raise fenoldopam levels by competing for the same sulfate pathway, but this is a minor, theoretical concern that your care team can handle with routine blood pressure and heart rate monitoring. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Fenoldopam interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Acetaminophen And Codeine and Fenoldopam interaction managed?
This is a minor, theoretical interaction, so it is usually managed with simple monitoring rather than avoiding either drug. Keep taking both medications exactly as prescribed unless your care team tells you otherwise. Because fenoldopam lowers blood pressure, your team may check your blood pressure and heart rate more closely and watch for symptoms like dizziness or a fast heartbeat. Your fenoldop… 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 Fenoldopam 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 anything you'd monitor while I'm on both?
References (1)
- Ziemniak JA, Allison N, Boppana VK, et al: The effect of acetaminophen on the disposition of fenoldopam: competition for sulfation. Clin Pharmacol Ther 1987; 41:275-281. PubMed
Keep reading about Acetaminophen And Codeine
Keep reading about Fenoldopam
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