Acetaminophen And Codeine and Rifampin: 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
Rifampin
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.
Rifampin can make your codeine work less well. Codeine is a prodrug, which means your body has to change it into morphine to relieve pain. Rifampin speeds up the liver enzymes that handle codeine, so less of it becomes active morphine. That can mean weaker pain relief. And if your body has gotten used to the codeine, this drop can even trigger uncomfortable withdrawal feelings like sweating, aches, or a racing heart.
The good news: this is manageable. Keep taking both medicines as prescribed, and let your care team know if your pain isn't controlled or you feel off. They can adjust your dose and watch you closely.
Effect: Rifampin (potent CYP3A4 inducer) increases codeine metabolism, shunting it toward norcodeine and reducing CYP2D6-mediated conversion to morphine. Codeine is a prodrug, so reduced morphine formation means decreased analgesic efficacy and possible withdrawal in physically dependent patients.
- Direction: reduced active opioid (morphine) exposure, reduced efficacy
- Onset: unspecified; expect over days of induction
- Evidence: theoretical
- Management: monitor for inadequate analgesia and withdrawal; codeine dose may need to be increased and individualized. If rifampin is discontinued, consider reducing codeine and monitor for sedation/respiratory depression as induction resolves.
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 lowers morphine levels. This can diminish effectiveness or trigger a withdrawal syndrome in patients who have become physically dependent. Should concurrent use be required, patients should be watched closely for reduced efficacy or indications of opioid withdrawal syndrome, and raising the codeine dose can be considered as needed. When a CYP3A4 inducer is being stopped, consider lowering the codeine dose and monitor patients carefully 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 medications as prescribed unless your prescriber tells you otherwise. Your care team can manage this combination.
- Watch for less pain relief or signs of opioid withdrawal (sweating, chills, body aches, restlessness, stomach upset, fast heartbeat).
- Your codeine dose may need to be adjusted and individualized by your care team, and they may monitor you more closely.
- Tell your team if rifampin is ever stopped, since codeine may become stronger again and your dose may need lowering to avoid excess sedation.
Raise any concerns with your pharmacist or prescriber before making changes.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Rifampin together?
Rifampin speeds up codeine breakdown, so less morphine is formed and your pain relief may weaken or withdrawal may start; keep taking both and ask your care team to adjust the dose or monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Rifampin 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 Rifampin interaction managed?
Keep taking both medications as prescribed unless your prescriber tells you otherwise. Your care team can manage this combination. Watch for less pain relief or signs of opioid withdrawal (sweating, chills, body aches, restlessness, stomach upset, fast heartbeat). Your codeine dose may need to be adjusted and individualized by your care team, and they may monitor you more closely. Tell your team i… 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 Rifampin 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 Rifampin
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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