Primidone and Naloxegol: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Primidone
Naloxegol
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.
What happens
Reduced naloxegol exposure and reduced efficacy of naloxegol
Interaction Deep Dive
Concomitant use of PHENobarbital (a CYP3A inducer) with naloxegol (a CYP3A substrate) may decrease naloxegol exposure, which may reduce the efficacy of naloxegol. If concomitant use cannot be avoided, closely monitor neonates and consider increasing the naloxegol dosage accordingly2.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of naloxegol
Literature reports
1 report — tap to read
a) Coadministration of once-daily oral rifampin 600 mg (a CYP3A inducer) and naloxegol 25 mg significantly decreased the naloxegol Cmax and AUC compared with naloxegol monotherapy 1.
Common questions
Can I take Primidone and Naloxegol together?
Reduced naloxegol exposure and reduced efficacy of naloxegol Always confirm with your pharmacist or prescriber before making any change.
How serious is the Primidone and Naloxegol 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 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 Primidone or Naloxegol 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: MOVANTIK(TM) oral tablets, naloxegol oral tablets. AstraZeneca (per manufacturer), Wilmington, DE, 2014. DailyMed
- Product Information: SEZABY(TM) intravenous injection, phenobarbital sodium intravenous injection. Sun Pharmaceutical Industries Inc (per manufacturer), Cranbury, NJ, 2022. DailyMed
Keep reading about Primidone
Keep reading about Naloxegol
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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