Acetaminophen And Codeine and Hydroxytryptophan: 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
Hydroxytryptophan
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.
Your pain medicine contains codeine, which (along with acetaminophen) can gently raise serotonin, a chemical messenger in your body. 5-HTP (hydroxytryptophan) is a supplement your body turns into serotonin. Taking both together can add up and, in rare cases, push serotonin too high. This is called serotonin syndrome.
Watch for signs like feeling agitated or restless, shivering, sweating, a fast heartbeat, muscle twitching, or a fever. This concern is theoretical, meaning it is based on how the drugs work rather than proven cases. The good news is your care team can manage this by watching you closely, especially when starting or adjusting doses. Please tell your pharmacist or doctor you take both.
Effect: Additive serotonergic activity, increasing the theoretical risk of serotonin syndrome.
Mechanism: Codeine has weak serotonergic properties; 5-HTP is a direct serotonin precursor, increasing central serotonin synthesis. Combined effect is additive (pharmacodynamic), not pharmacokinetic. Acetaminophen is not implicated.
- Direction: Increased serotonergic tone.
- Onset: Unspecified; higher risk at initiation and dose escalation.
- Evidence: Theoretical.
- Management: If co-used, monitor for hyperreflexia, clonus, autonomic instability, hyperthermia, agitation. Discontinue codeine if serotonin syndrome is suspected and treat supportively.
What happens
Increased risk of serotonin syndrome
Interaction Deep Dive
Serotonin syndrome has been reported when opioids like codeine are taken together with serotonergic agents. When such combined use cannot be avoided, monitor the patient closely, especially when starting therapy and when doses are being changed. Should serotonin syndrome be suspected, stop codeine123.
Why it happens (mechanism)
Additive serotonergic effects
How to manage this interaction
If you have been prescribed acetaminophen with codeine and also take the 5-HTP supplement, keep taking both as directed unless your care team tells you otherwise.
- Let your pharmacist and prescriber know you use both so they can watch you more closely, especially when starting or adjusting doses.
- Watch for restlessness, sweating, shivering, muscle twitching, a racing heart, or fever.
- Seek care promptly if these symptoms appear, since codeine may need to be stopped if serotonin syndrome is suspected.
Any dose changes should be individualized by your care team.
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 Hydroxytryptophan together?
Codeine plus the 5-HTP supplement can add up to raise serotonin and, in rare cases, cause serotonin syndrome; keep taking both as prescribed but tell your care team and watch for symptoms like agitation, sweating, tremor, or fever. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Hydroxytryptophan 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 Hydroxytryptophan interaction managed?
If you have been prescribed acetaminophen with codeine and also take the 5-HTP supplement, keep taking both as directed unless your care team tells you otherwise. Let your pharmacist and prescriber know you use both so they can watch you more closely, especially when starting or adjusting doses. Watch for restlessness, sweating, shivering, muscle twitching, a racing heart, or fever. Seek care prom… 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 Hydroxytryptophan 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 (3)
- Product Information: Codeine sulfate oral tablets, codeine sulfate oral tablets. West-Ward Pharmaceuticals Corp (per DailyMed), Eatontown, NJ, 2016. DailyMed
- 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
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