Abrocitinib and Phenobarbital: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 10, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Phenobarbital
Abrocitinib
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.
These two medicines can work against each other. Phenobarbital speeds up the liver enzymes that break down abrocitinib (Cibinqo), the medicine used for eczema. When abrocitinib is cleared out faster, less of it stays in your body, so it may not control your skin symptoms as well.
It's worth noting this is based on how the drugs are expected to behave (theoretical), not on strong studies. Still, please don't change anything on your own. Let your pharmacist or doctor know you take both. They can watch how well your eczema is controlled and adjust your dose if needed so the treatment keeps working for you.
Effect: Reduced abrocitinib exposure and potential loss of efficacy.
Mechanism: Phenobarbital induces CYP2C9 and CYP2C19; abrocitinib is a CYP2C9/CYP2C19 substrate, so induction increases its clearance and lowers AUC/Cmax of active moiety.
- Direction: Reduced abrocitinib effect (pharmacokinetic).
- Onset: Unspecified; enzyme induction typically develops over days to weeks.
- Evidence: Theoretical.
- Management: If co-use is unavoidable, monitor for reduced disease control and consider individualized abrocitinib dose adjustment. Monitor neonates closely where relevant.
What happens
Reduced abrocitinib exposure and reduced efficacy of abrocitinib
Interaction Deep Dive
Taking PHENobarbital, which induces CYP2C9/CYP2C19, together with abrocitinib, a substrate of CYP2C9/CYP2C19, can lower abrocitinib exposure and potentially diminish its effectiveness. When this combination is unavoidable, monitor neonates carefully and think about raising the abrocitinib dose as appropriate1.
Why it happens (mechanism)
Induction of CYP2C9-mediated metabolism of abrocitinib; induction of CYP2C19-mediated metabolism of abrocitinib
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. The concern is that phenobarbital may make abrocitinib less effective over time.
- Tell your pharmacist and prescriber that you take both drugs.
- Watch for signs your eczema is not as well controlled, and report this.
- Your abrocitinib dose may need to be adjusted and individualized by your care team, and they may monitor your response more closely.
- If a newborn is involved (neonatal exposure), close monitoring is advised.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Abrocitinib and Phenobarbital together?
Phenobarbital can speed up how your body clears abrocitinib, which may make your eczema medicine less effective. Keep taking both as prescribed and ask your care team whether your abrocitinib dose or monitoring needs adjusting. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Abrocitinib and Phenobarbital 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 Abrocitinib and Phenobarbital interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. The concern is that phenobarbital may make abrocitinib less effective over time. Tell your pharmacist and prescriber that you take both drugs. Watch for signs your eczema is not as well controlled, and report this. Your abrocitinib dose may need to be adjusted and individualized by your care team, and they may moni… 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 Abrocitinib or Phenobarbital 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 (1)
- Product Information: SEZABY(TM) intravenous injection, phenobarbital sodium intravenous injection. Sun Pharmaceutical Industries Inc (per manufacturer), Cranbury, NJ, 2022. DailyMed
Keep reading about Phenobarbital
Keep reading about Abrocitinib
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