Grapefruit Juice and Acetaminophen And Codeine: 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
Grapefruit Juice
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, which your body turns into morphine to relieve pain. Grapefruit juice can slow down one of the liver enzymes (called CYP3A4) that helps clear codeine. When that pathway is slowed, more codeine and morphine can build up in your blood.
That extra buildup can make the medicine's effects stronger, so you might feel very sleepy or notice your breathing slowing down. This is mostly a theoretical concern, but because it involves an opioid, it is worth taking seriously. Please don't change anything on your own. Talk with your pharmacist or doctor, and they can adjust the dose and watch you more closely if needed.
Effect: Grapefruit juice inhibits CYP3A4, reducing metabolism of codeine and increasing exposure to codeine and its active metabolite morphine.
- Direction: Increased opioid effect (both parent drug and active metabolite accumulate). CYP2D6 remains the primary bioactivation route to morphine; CYP3A4 inhibition shifts more codeine toward that pathway and raises overall exposure.
- Risk: Enhanced/prolonged sedation and potentially fatal respiratory depression, particularly when the inhibitor is added to a stable codeine dose.
- Evidence: Theoretical; onset unspecified.
- Management: If coadministered, consider reduced codeine dose with frequent monitoring for sedation and respiratory depression. On inhibitor discontinuation, monitor for withdrawal and reassess dose.
What happens
Increased codeine and morphine exposure
Interaction Deep Dive
Taking codeine together with a CYP3A4 inhibitor, such as grapefruit juice, can raise the plasma levels of both the parent compound (codeine) and its active metabolite (morphine). This elevation may intensify or extend adverse effects and has the potential to produce fatal respiratory depression, especially if the inhibitor is introduced once a patient has already reached a stable codeine dose. Should combined use be required, a reduction in the codeine dose should be considered, along with frequent monitoring for sedation and respiratory depression. If a concurrent CYP3A4 inhibitor is stopped, consider raising the codeine dose and watch for indications of opioid withdrawal12.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated codeine metabolism 5-Hydroxyindoleacetic acid measurement Uric acid measurement
How to manage this interaction
You can keep taking your medication as prescribed. The key is not to make changes on your own, but to let your care team know about grapefruit juice intake so they can manage it.
- Tell your pharmacist or prescriber if you regularly drink grapefruit juice or eat grapefruit.
- Your team may adjust and individualize your codeine dose and monitor you more closely for sedation and slowed breathing.
- Watch for extreme drowsiness, confusion, or trouble breathing, and seek help right away if these occur.
- If you stop grapefruit after being stable on both, mention it, as your dose may need review to avoid reduced pain control or withdrawal.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Grapefruit Juice and Acetaminophen And Codeine together?
Grapefruit juice can raise codeine and morphine levels, increasing the risk of heavy sedation or slowed breathing. Keep taking your medicine as prescribed and tell your pharmacist or doctor about grapefruit use so they can adjust the dose and monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Grapefruit Juice and Acetaminophen And Codeine 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 Grapefruit Juice and Acetaminophen And Codeine interaction managed?
You can keep taking your medication as prescribed. The key is not to make changes on your own, but to let your care team know about grapefruit juice intake so they can manage it. Tell your pharmacist or prescriber if you regularly drink grapefruit juice or eat grapefruit. Your team may adjust and individualize your codeine dose and monitor you more closely for sedation and slowed breathing. Watch… 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 Grapefruit Juice or Acetaminophen And Codeine 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
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