Acetaminophen And Codeine and Ritlecitinib: 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
Ritlecitinib
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. Ritlecitinib (Litfulo) can slow down one of the liver enzymes that breaks codeine down. That means more codeine and morphine can build up in your body than usual.
Because of this, you could feel more drowsy or, in serious cases, your breathing could slow down too much. This matters most if the Litfulo is added after you have been taking codeine for a while. The good news is your care team can manage this by watching you closely and adjusting your codeine dose if needed. Please don't stop either medicine on your own, just talk with your doctor or pharmacist.
Effect: Ritlecitinib (a CYP3A4 inhibitor) may reduce CYP3A4-mediated codeine clearance, increasing codeine and its active metabolite morphine exposure.
- Direction: Increased opioid exposure and effect (risk of sedation and potentially fatal respiratory depression).
- Evidence: Theoretical; magnitude not quantified.
- Onset: Unspecified; risk greatest when inhibitor is added to a stable codeine regimen.
- Management: Monitor for respiratory depression and sedation; consider codeine dose reduction until stable effects are seen. If ritlecitinib is discontinued, monitor for opioid withdrawal and consider increasing codeine dose.
Note: Codeine is a prodrug, but analgesia depends on CYP2D6 activation to morphine; CYP3A4 inhibition here reduces clearance and raises overall opioid levels.
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, which may intensify or extend adverse effects and can produce respiratory depression that is potentially fatal, especially in cases where the inhibitor is introduced after a patient has reached a stable codeine dose. When these agents must be given together, watch patients carefully for sedation and respiratory depression, and think about lowering the codeine dose until the drug's effects have stabilized. Conversely, when a CYP3A4 inhibitor is being withdrawn, observe patients for indications of opioid withdrawal, and consider raising the codeine dose until stable drug effects are seen12.
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. Here is what your team may do:
- Watch you more closely for excess drowsiness or slowed breathing, especially right after starting Litfulo.
- Adjust and individualize your codeine dose (often lowering it) until they see how you respond.
- If Litfulo is later stopped, watch for signs your codeine effect is fading and adjust the dose as needed.
Tell your pharmacist or doctor right away if you feel unusually sleepy, confused, or short of breath. Bring up any new medicines so they can plan ahead.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Ritlecitinib together?
Ritlecitinib can raise codeine and morphine levels, increasing the risk of heavy sedation and slowed breathing. Keep taking both as prescribed, watch for drowsiness or breathing trouble, and let your care team adjust and monitor your codeine dose. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Ritlecitinib 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 Ritlecitinib interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Here is what your team may do: Watch you more closely for excess drowsiness or slowed breathing, especially right after starting Litfulo. Adjust and individualize your codeine dose (often lowering it) until they see how you respond. If Litfulo is later stopped, watch for signs your codeine effect is fading… 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 Ritlecitinib 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 Ritlecitinib
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