Acetaminophen And Codeine and Maribavir: 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
Maribavir
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, and your body has to change codeine into its active pain-relieving form (mostly morphine). Maribavir can slow down one of the enzymes that helps break codeine down, so more codeine and morphine may build up in your body than usual.
If that happens, you could feel more of codeine's effects, like heavy drowsiness or slowed, shallow breathing. This is based mainly on theory rather than lots of real-world cases, but it is worth taking seriously because breathing problems can be dangerous. Do not stop either medicine on your own. Your care team can manage this safely by watching you closely and adjusting your codeine dose if needed.
Effect: Maribavir inhibits CYP3A4, which contributes to codeine metabolism, potentially increasing codeine and morphine exposure and enhancing/prolonging opioid effects, including sedation and respiratory depression.
- Mechanism: CYP3A4 inhibition reduces oxidative clearance of codeine, raising parent and active metabolite (morphine) concentrations.
- Direction: Increased opioid effect.
- Onset: Unspecified; risk is highest when the inhibitor is added to a stable codeine regimen.
- Evidence: Theoretical; severity rated major.
- Management: Monitor for respiratory depression and sedation; consider reducing codeine dose until stable effects are seen. If maribavir is stopped, monitor for withdrawal and consider increasing codeine.
What happens
Increased codeine and morphine exposure
Interaction Deep Dive
Taking codeine together with CYP3A4 inhibitors has led to elevated levels of both codeine and morphine, an effect that may intensify or extend adverse reactions and carries the potential for fatal respiratory depression, especially in cases where the inhibitor is introduced after the patient has already reached a stable codeine dose. When the combination cannot be avoided, patients should be watched closely for sedation and respiratory depression, and reducing the codeine dose should be considered until steady drug effects are seen. Should a CYP3A4 inhibitor be withdrawn, watch 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 as prescribed unless your prescriber tells you otherwise. This interaction can usually be managed with a few steps.
- Your team may watch you more closely for extra sleepiness or slow, shallow breathing, especially soon after maribavir is started.
- Your codeine dose may be adjusted and individualized by your care team until your response is stable.
- If maribavir is later stopped, your team may watch for opioid withdrawal and adjust codeine again.
Call your pharmacist or prescriber right away if you notice unusual drowsiness, confusion, or trouble breathing.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Maribavir together?
Maribavir may raise codeine and morphine levels by slowing codeine's breakdown, which can increase drowsiness and dangerous breathing problems; keep taking both as prescribed and let your care team monitor you and adjust the codeine dose as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Maribavir 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 Maribavir interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction can usually be managed with a few steps. Your team may watch you more closely for extra sleepiness or slow, shallow breathing, especially soon after maribavir is started. Your codeine dose may be adjusted and individualized by your care team until your response is stable. If maribavir is later sto… 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 Maribavir 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 Maribavir
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