Dantrolene and Acetaminophen And Codeine: 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
Dantrolene
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.
You've been prescribed acetaminophen with codeine (a pain medicine that contains an opioid) along with dantrolene (a muscle relaxer). Both of these can slow your breathing on their own. When taken together, that effect can add up, so your breathing could become slower or shallower than you'd expect from either one alone.
This concern is based mostly on how these medicines work, not on a lot of real-world reports, but it's still worth taking seriously. Keep taking both exactly as prescribed and don't change anything on your own. Watch for unusual sleepiness, slow breathing, or trouble waking up, and let your care team know. They can manage this safely by adjusting doses and keeping a closer eye on you.
Effect: Additive CNS and respiratory depression when codeine (opioid analgesic) is combined with the skeletal muscle relaxant dantrolene, with a theoretical enhancement of neuromuscular depressant effects.
- Mechanism: Enhanced neuromuscular blocking/depressant action plus additive opioid-mediated respiratory depression (PD interaction, not PK).
- Direction: Increased degree of respiratory depression.
- Evidence: Theoretical; onset unspecified. Severity rated major given the clinical stakes.
- Management: Monitor for greater-than-expected respiratory depression and sedation. Dose of codeine and/or dantrolene may need individualized reduction. Consider prescribing naloxone for emergency opioid overdose treatment.
What happens
Increased risk of respiratory depression
Interaction Deep Dive
Concomitant use of codeine with skeletal muscle relaxants such as dantrolene may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression. Monitor patients for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of codeine and/or the muscle relaxant as necessary. Due to the risk of respiratory depression with concomitant use of skeletal muscle relaxants and opioids, consider prescribing naloxone for the emergency treatment of opioid overdose12.
Why it happens (mechanism)
Enhanced neuromuscular blocking action of dantrolene
How to manage this interaction
Your care team can manage this combination safely. Here's what typically happens and what you can do:
- Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may adjust and individualize the dose of the codeine and/or the dantrolene, and may monitor you more closely for slowed breathing or heavy sedation.
- Your prescriber may also offer naloxone to have on hand for emergencies.
- Watch for very slow or shallow breathing, extreme drowsiness, or difficulty waking. Avoid alcohol and other sedatives.
Raise any breathing or sleepiness concerns with your pharmacist or prescriber right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Dantrolene and Acetaminophen And Codeine together?
Combining acetaminophen/codeine with dantrolene can add up to slow your breathing, so watch for excess drowsiness or slow breathing and let your care team adjust doses and monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dantrolene and Acetaminophen And Codeine 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 Dantrolene and Acetaminophen And Codeine interaction managed?
Your care team can manage this combination safely. Here's what typically happens and what you can do: Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise. Your team may adjust and individualize the dose of the codeine and/or the dantrolene, and may monitor you more closely for slowed breathing or heavy sedation. Your prescriber may also offer naloxone to have on han… 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 Dantrolene or Acetaminophen And Codeine 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 Dantrolene
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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