Acetaminophen And Codeine and Rolapitant: 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
Rolapitant
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.
Here's what's going on. Codeine is a "prodrug," which means your body has to convert it into morphine before it can relieve pain. That conversion depends on a liver enzyme called CYP2D6. Rolapitant (Varubi), an anti-nausea medicine, can slow that enzyme down.
Because of this, your body may make less morphine from the codeine. That can mean weaker pain relief, and if you take codeine regularly, you might even notice mild withdrawal-type feelings. The good news is this is a theoretical concern, and your care team can manage it by watching how you feel and adjusting your dose if needed. Please talk with your pharmacist or doctor before changing anything.
Mechanism: Codeine is a prodrug requiring CYP2D6-mediated O-demethylation to morphine, its active metabolite. Rolapitant inhibits CYP2D6, so codeine exposure rises while morphine (active metabolite) exposure falls.
Direction/effect: Reduced analgesic efficacy and possible opioid withdrawal in tolerant patients (not increased opioid effect).
- Evidence: Theoretical; onset unspecified.
- Severity: Major.
- Management: If co-use is necessary, monitor for inadequate analgesia and withdrawal; codeine dose may be increased and individualized. On rolapitant discontinuation, morphine formation can rebound, so consider reducing codeine dose and monitor for sedation and respiratory depression.
What happens
Increased codeine exposure and reduced active metabolite (morphine) exposure
Interaction Deep Dive
When codeine is taken together with a CYP2D6 inhibitor, the plasma levels of morphine, which is codeine's active metabolite, may fall, a change that could diminish therapeutic effect and provoke withdrawal symptoms. Should the combination be required, watch patients for signs of withdrawal and think about raising the codeine dose. After the CYP2D6 inhibitor is stopped, consider lowering the codeine dose and observe for indications of respiratory depression and sedation312.
Why it happens (mechanism)
Inhibition of CYP2D6-mediated codeine metabolism
How to manage this interaction
Keep taking both as prescribed unless your care team tells you otherwise. This interaction can usually be managed with monitoring and dose tailoring.
- Watch for weaker pain relief or withdrawal-type symptoms (restlessness, sweating, aches) while taking rolapitant.
- Your codeine dose may need to be adjusted and individualized by your care team if pain control drops off.
- When rolapitant is stopped, morphine levels can rise again, so your team may lower the codeine dose and watch for excess sedation or slowed breathing.
Report any changes in pain control or how sleepy you feel to your pharmacist or prescriber.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Rolapitant together?
Rolapitant can block the enzyme that turns codeine into morphine, so your codeine may work less well; your care team can manage this by monitoring you and adjusting the dose as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Rolapitant 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 Rolapitant interaction managed?
Keep taking both as prescribed unless your care team tells you otherwise. This interaction can usually be managed with monitoring and dose tailoring. Watch for weaker pain relief or withdrawal-type symptoms (restlessness, sweating, aches) while taking rolapitant. Your codeine dose may need to be adjusted and individualized by your care team if pain control drops off. When rolapitant is stopped, mo… 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 Rolapitant 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 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
- Product Information: codeine sulfate oral tablets, codeine sulfate oral tablets. West-Ward Pharmaceuticals Corp. (per FDA), Eatontown, NJ, 2017. DailyMed
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