Acetaminophen And Codeine and Oxcarbazepine: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 1, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acetaminophen And Codeine
Oxcarbazepine
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 change it into the active painkiller (morphine) before it works. Oxcarbazepine (Trileptal, Oxtellar) can speed up one of the liver pathways that handles codeine. In theory, that can lower how much of the active pain relief you actually get.
If you take both, your codeine may work less than expected. And if your body is used to the codeine, you could feel mild withdrawal-type symptoms. This is based on theory, not strong studies, so please don't change anything on your own. Your care team can manage it easily by adjusting your dose and keeping an eye on how well your pain is controlled.
Mechanism: Oxcarbazepine is a CYP3A4 inducer. Codeine is a prodrug; CYP3A4 induction shifts metabolism toward inactive norcodeine and reduces substrate available for CYP2D6-mediated conversion to morphine, lowering active opioid exposure.
- Direction: reduced codeine/morphine exposure, reduced analgesia, possible withdrawal in physically dependent patients.
- Evidence: theoretical; magnitude not quantified.
- Onset: unspecified (induction is typically gradual over days to weeks).
- Management: monitor for loss of efficacy and withdrawal signs; codeine dose may need to be adjusted and individualized. If oxcarbazepine is stopped, anticipate rising opioid effect and monitor for sedation/respiratory depression, with codeine dose reduction as appropriate.
What happens
Reduced codeine and morphine exposure, reduced opioid efficacy and precipitation of opioid withdrawal
Interaction Deep Dive
When codeine is taken together with CYP3A4 inducers, codeine concentrations can fall while norcodeine concentrations rise, and CYP2D6-mediated metabolism decreases, which in turn lowers morphine levels. This can lessen therapeutic effect or trigger a withdrawal syndrome in patients who have become physically dependent. Should combined use be necessary, watch patients carefully for reduced efficacy or indications of opioid withdrawal syndrome, and raise the codeine dose if required. When a CYP3A4 inducer is being stopped, consider lowering the codeine dose and monitor patients closely for signs of respiratory depression or sedation12.
Why it happens (mechanism)
Induction of CYP3A4-mediated codeine metabolism
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction can usually be managed with a few simple steps.
- Your care team may monitor how well your pain is controlled and watch for signs your codeine is working less than expected.
- Watch for opioid withdrawal-type symptoms (restlessness, sweating, chills, muscle aches, stomach upset) and report them.
- Your codeine dose may need to be adjusted and individualized by your team.
- If oxcarbazepine is ever stopped, tell your team, since your codeine may then feel stronger and the dose may need lowering.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Oxcarbazepine together?
Oxcarbazepine may speed up codeine's breakdown and lower its pain relief, possibly causing withdrawal if you depend on it. Keep taking both as prescribed and tell your care team if your pain control worsens so they can adjust and monitor. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Oxcarbazepine 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 Oxcarbazepine interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction can usually be managed with a few simple steps. Your care team may monitor how well your pain is controlled and watch for signs your codeine is working less than expected. Watch for opioid withdrawal-type symptoms (restlessness, sweating, chills, muscle aches, stomach upset) and report them. Your… 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 Oxcarbazepine 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 (2)
- 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 Oxcarbazepine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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