Acetaminophen And Codeine and Morphine: 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
Morphine
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.
Both of these are opioid pain medicines. Your Tylenol with codeine already contains codeine, which is an opioid, and morphine is a stronger opioid. Taking them together stacks their effects. That means more drowsiness, slower breathing, low blood pressure, and in serious cases a dangerous slowdown of breathing that can be life threatening.
There is also a small, mostly theoretical chance of serotonin syndrome, which can cause agitation, shivering, a fast heartbeat, or confusion.
Please don't stop or change either medicine on your own. Your care team can manage this safely by using the lowest doses needed and watching you closely. Talk with your doctor or pharmacist about your combination.
Additive CNS and respiratory depression from two opioids (codeine plus morphine), along with a theoretical additive serotonergic risk.
- Direction: Enhanced sedation, respiratory depression, hypotension, and increased opioid-overdose potential; possible serotonin syndrome.
- Mechanism: Pharmacodynamic additivity (opioid CNS depression; serotonergic effects). Not a CYP-mediated PK interaction.
- Evidence: Theoretical; severity major.
- Management: Reserve concomitant use for when alternatives are inadequate. Use lowest effective dose and shortest duration. Monitor for sedation, respiratory depression, and serotonin syndrome, especially at initiation and dose changes. Consider prescribing naloxone. Discontinue if serotonin syndrome is suspected.
What happens
Increased risk of respiratory and CNS depression and an increased risk of serotonin syndrome
Interaction Deep Dive
Taking morphine together with serotonergic CNS depressants can heighten the likelihood of respiratory depression, deep sedation, hypotension, coma, opioid overdose, and serotonin syndrome. Combined administration of morphine with CNS depressants should be limited to patients for whom other options are insufficient. When such combined use cannot be avoided, employ the lowest dose and briefest duration needed to reach therapeutic objectives, and monitor carefully for sedation, respiratory depression, and any signs or symptoms of serotonin syndrome. The patient should be watched closely, especially when therapy begins and when doses are being adjusted. Should serotonin syndrome be suspected, stop morphine1. Concurrent morphine and CNS depressant use raises the risk of opioid overdose, so prescribing naloxone for emergency management of opioid overdose should be considered 2. When starting a morphine/naltrexone combination, begin at one-third to one-half of the standard morphine/naltrexone dose 3. When starting Morphabond ER(TM), initiate at the lowest feasible dose of 15 mg every 12 hours, and consider a reduced dosage of the concomitant CNS depressant 4.
Why it happens (mechanism)
Additive CNS depression; additive serotonergic effects
How to manage this interaction
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. This combination can be managed with care.
- Your care team will likely use the lowest doses for the shortest time needed, and doses may be adjusted and individualized to you.
- Expect closer monitoring, especially when starting or changing a dose, for heavy drowsiness, slow or shallow breathing, or confusion.
- Ask your prescriber whether having naloxone on hand is right for you.
- Seek urgent help for very slow breathing, extreme sleepiness, or agitation, shivering, and racing heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
Common questions
Can I take Acetaminophen And Codeine and Morphine together?
Combining Tylenol with codeine and morphine stacks two opioids, raising the risk of excessive sedation and dangerously slow breathing, so use only under close medical supervision and never adjust doses yourself. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Morphine 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 Morphine interaction managed?
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. This combination can be managed with care. Your care team will likely use the lowest doses for the shortest time needed, and doses may be adjusted and individualized to you. Expect closer monitoring, especially when starting or changing a dose, for heavy drowsiness, slow or shallow breathing, or confusion. Ask your… 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 Morphine 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 (6)
- Product Information: KADIAN(R) oral extended-release capsules, morphine sulfate oral extended-release capsules. Allergan USA, Inc (per FDA), Irvine, CA, 2016. DailyMed
- Product Information: DURAMORPH intravenous, epidural, intrathecal injection, morphine sulfate intravenous, epidural, intrathecal injection. Hikma Pharmaceuticals USA Inc (Per FDA), Berkeley, NJ, 2023. DailyMed
- Product Information: EMBEDA(R) oral extended-release capsules, morphine sulfate naltrexone HCl oral extended-release capsules. Pfizer Inc. (per FDA), New York, NY, 2016. DailyMed
- Product Information: MORPHABOND(TM) ER oral extended-release tablets, morphine sulfate oral extended-release tablets. Daiichi Sankyo Inc (per FDA), Basking Ridge, NJ, 2018. DailyMed
- Product Information: MS CONTIN(R) oral extended-release tablets, morphine sulfate oral extended-release tablets. Purdue Pharma LP (per FDA), Stamford, CT, 2023. DailyMed
- Product Information: Morphine sulfate oral solution, morphine sulfate oral solution. Hikma Pharmaceuticals USA Inc (per FDA), Berkeley Heights, NJ, 2023. DailyMed
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