Acetaminophen And Codeine and Paritaprevir: 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
Paritaprevir
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.
One of your medicines contains codeine, which your body turns into morphine to relieve pain. Paritaprevir can slow down the enzyme that helps clear codeine and morphine, so more of these can build up in your body.
When that happens, you might feel extra sleepy or drowsy, and in serious cases your breathing could slow down too much. This is worth taking seriously, but it is very manageable. Your care team can watch you more closely and adjust your codeine dose so you stay comfortable and safe. Please talk with your pharmacist or doctor before making any changes, and let them know right away if you feel unusually sleepy or short of breath.
Effect: Increased codeine and morphine exposure via inhibition of CYP3A4-mediated codeine metabolism by paritaprevir.
Direction: Codeine is normally partly N-demethylated by CYP3A4 to norcodeine, with CYP2D6 producing the active morphine. CYP3A4 inhibition shunts more codeine toward morphine and raises overall opioid exposure, increasing sedation and potentially fatal respiratory depression, especially when the inhibitor is added to a stable codeine dose.
Evidence: Theoretical; severity rated major. Onset unspecified.
- Monitor for respiratory depression and sedation.
- Consider codeine dose reduction until stable effects observed.
- On inhibitor discontinuation, monitor for opioid withdrawal and consider dose increase.
What happens
Increased codeine and morphine exposure
Interaction Deep Dive
Taking codeine together with CYP3A4 inhibitors has produced elevated levels of both codeine and morphine, an effect that may intensify or extend adverse reactions and can lead to respiratory depression that is potentially fatal, especially in cases where the inhibitor is introduced once a stable codeine dose has already been established. When such combined use cannot be avoided, patients should be watched closely for sedation and respiratory depression, and reducing the codeine dose should be considered until stable drug effects are seen. Conversely, when a CYP3A4 inhibitor is being stopped, monitor patients for indications of opioid withdrawal and consider raising the codeine dose until stable drug effects have been observed12.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated codeine metabolism
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination can be managed with the right attention.
- Your team may monitor you more closely for excess drowsiness, heavy sedation, or slowed breathing.
- Your codeine dose may be adjusted and individualized by your prescriber until your response is stable.
- If paritaprevir is later stopped, your team may watch for signs of opioid withdrawal and adjust again.
Contact your pharmacist or doctor promptly if you feel unusually sleepy, confused, or short of breath, and before making any dose changes yourself.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Paritaprevir together?
Paritaprevir can raise codeine and morphine levels and increase the risk of dangerous sedation or slowed breathing, so your care team may adjust your codeine dose and monitor you more closely. Report any unusual drowsiness or breathing trouble right away. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Paritaprevir 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 Paritaprevir interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination can be managed with the right attention. Your team may monitor you more closely for excess drowsiness, heavy sedation, or slowed breathing. Your codeine dose may be adjusted and individualized by your prescriber until your response is stable. If paritaprevir is later stopped, your team may… 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 Paritaprevir 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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