Acetaminophen And Codeine and Lamotrigine: 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
Lamotrigine
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're taking acetaminophen with codeine (a pain reliever) and lamotrigine (Lamictal), which is often used for seizures or mood. The acetaminophen part may cause your body to clear lamotrigine a little faster, which could make lamotrigine slightly weaker over time.
The good news is that this effect is small. In studies, lamotrigine levels dropped only a little, and an occasional dose of acetaminophen is unlikely to matter much. If you're using it regularly, just let your care team know. They can watch how well your lamotrigine is working and adjust things if needed. Please don't change either medicine on your own.
Effect: Acetaminophen may modestly reduce lamotrigine exposure. In a randomized study, coadministration decreased lamotrigine half-life by ~15% and AUC by ~20%, with a ~7% increase in renal clearance.
Mechanism: Increased renal clearance of lamotrigine (the codeine component is not implicated here). Neither agent's active moiety depends on the affected pathway in a way that flips direction.
- Direction: reduced lamotrigine effect (PK, modest magnitude)
- Onset: delayed; Evidence: theoretical/weak
- Management: Monitor clinical response (seizure or mood control). Routine dose increases unnecessary; escalate only if therapeutic failure. Occasional acetaminophen use is clinically insignificant.
What happens
Decreased lamotrigine effectiveness
Interaction Deep Dive
A randomized study looked at how acetaminophen affects the pharmacokinetics of lamotrigine. With simultaneous administration, lamotrigine's area under the plasma concentration-time curve fell by 20% and its half-life fell by 15%. Meanwhile, renal clearance of lamotrigine rose by 7%1.
Why it happens (mechanism)
Increased renal clearance
How to manage this interaction
Keep taking both medications exactly as prescribed. This is a minor, mainly theoretical interaction, and an occasional dose of acetaminophen is unlikely to meaningfully lower your lamotrigine levels.
- If you use acetaminophen regularly (daily or near-daily), mention it to your pharmacist or prescriber.
- Your care team may monitor how well your lamotrigine is controlling your seizures or mood.
- Routine lamotrigine dose increases are usually not needed. If your team sees signs it isn't working as well, the dose can be adjusted and individualized for you.
- Report any breakthrough seizures or mood changes.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Acetaminophen increases the urinary clearance of lamotrigine following single doses of the anticonvulsant. In healthy volunteers, giving a single 300 mg dose of lamotrigine followed by acetaminophen 900 mg 3 times daily produced reductions in AUC and serum half-life of 20% and 15%, respectively, when compared with giving lamotrigine alongside placebo. No changes in peak plasma concentration or time to peak were seen. The proportion of lamotrigine recovered in the urine was likewise greater when it was given with acetaminophen. It was proposed that acetaminophen may increase the elimination of lamotrigine from the circulation 1.
Common questions
Can I take Acetaminophen And Codeine and Lamotrigine together?
Acetaminophen may slightly lower lamotrigine levels, but the effect is small and occasional use is unlikely to matter. Keep taking both as prescribed and tell your care team if you use acetaminophen regularly. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Lamotrigine interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Acetaminophen And Codeine and Lamotrigine interaction managed?
Keep taking both medications exactly as prescribed. This is a minor, mainly theoretical interaction, and an occasional dose of acetaminophen is unlikely to meaningfully lower your lamotrigine levels. If you use acetaminophen regularly (daily or near-daily), mention it to your pharmacist or prescriber. Your care team may monitor how well your lamotrigine is controlling your seizures or mood. Routin… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Acetaminophen And Codeine or Lamotrigine 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 anything you'd monitor while I'm on both?
References (1)
- Depot M, Powell JR, & Messenheimer JA: Kinetic effects of multiple oral doses of acetaminophen on a single oral dose of lamotrigine. Clin Pharmacol Ther 1990; 48:346-355. PubMed
Keep reading about Acetaminophen And Codeine
Keep reading about Lamotrigine
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major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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