Benzphetamine and Acetaminophen And Codeine: 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
Benzphetamine
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.
You've been prescribed acetaminophen with codeine (a pain reliever) along with benzphetamine (a weight-loss medicine). Both can raise a brain chemical called serotonin. When two medicines do this together, there's a small chance of something called serotonin syndrome. Warning signs can include feeling agitated or shaky, a fast heartbeat, sweating, muscle twitching, or confusion.
This concern is based on theory, not on lots of real cases, so please don't worry. Keep taking both exactly as prescribed. Your care team can watch you more closely, especially when you first start or change a dose. If any of those symptoms show up, reach out to your doctor or pharmacist right away.
Effect: Additive serotonergic activity may increase the risk of serotonin syndrome. Codeine has weak serotonergic properties, and benzphetamine (a sympathomimetic amphetamine derivative) can increase monoamine release.
- Direction: Additive PD interaction, not PK. Combined serotonergic burden increases risk.
- Onset: Unspecified; highest risk at initiation and dose escalation.
- Evidence: Theoretical.
- Management: If co-administered, monitor for autonomic instability, neuromuscular signs (clonus, hyperreflexia, rigidity), and mental status changes. Discontinue codeine if serotonin syndrome is suspected. Dose may be individualized by the care team.
What happens
Increased risk of serotonin syndrome
Interaction Deep Dive
Concomitant use of opioids, such as codeine, with serotonergic drugs has resulted in serotonin syndrome. If concomitant use is needed, carefully observe the patient, particularly during treatment initiation and dose adjustments. Discontinue codeine if serotonin syndrome is suspected123.
Why it happens (mechanism)
Additive serotonergic effects
How to manage this interaction
Here's how a care team usually handles this combination:
- Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may monitor you more closely, especially when you start either drug or change a dose.
- Doses can be adjusted and individualized by your care team if needed.
- If serotonin syndrome is suspected, your prescriber may stop the codeine.
Tell your pharmacist or doctor promptly if you notice agitation, confusion, a racing heart, heavy sweating, tremor, or muscle twitching.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
Common questions
Can I take Benzphetamine and Acetaminophen And Codeine together?
Taking acetaminophen with codeine alongside benzphetamine may add up to raise serotonin, so watch for agitation, fast heartbeat, sweating, or muscle twitching and report them promptly. Keep taking both as prescribed and let your care team monitor and adjust as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Benzphetamine 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 Benzphetamine and Acetaminophen And Codeine interaction managed?
Here's how a care team usually handles this combination: Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise. Your team may monitor you more closely, especially when you start either drug or change a dose. Doses can be adjusted and individualized by your care team if needed. If serotonin syndrome is suspected, your prescriber may stop the codeine. Tell your pharmaci… 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 Benzphetamine 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 (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
Keep reading about Acetaminophen And Codeine
Keep reading about Benzphetamine
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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