Felbamate and Phenobarbital Interaction
Drug interaction information between Felbamate and Phenobarbital.
Felbamate and Phenobarbital have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Felbamate and Phenobarbital. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Felbamate causes the level of phenobarbital in your blood to rise.
What To Do
Your doctor may need to lower your phenobarbital dose and monitor your blood levels closely.
FDA Label Information
CBZ epoxide ↓ ↑ ↓ Phenobarbital ↑ ↓ Specific Effects of Felbamate on Other Antiepileptic Drugs Phenytoin Felbamate causes an increase in steady-state phenytoin plasma concentrations. Phenobarbital Coadministration of felbamate with phenobarbital causes an increase in phenobarbital plasma concentrations. In 12 otherwise healthy male volunteers ingesting phenobarbital, the steady-state trough (C min ) phenobarbital concentration was 14.2 micrograms/mL.
Felbamate Also Interacts With
- Clonazepam major
- Erythromycin minor
- Carbamazepine minor
- Drospirenone/Ethinyl Estradiol minor
- Estradiol minor
Phenobarbital Also Interacts With
- Nirmatrelvir/Ritonavir major
- Ranolazine major
- Voriconazole major
- Canagliflozin moderate
- Cenobamate moderate
Frequently Asked Questions
Can I take Felbamate and Phenobarbital together?
This is a minor interaction. Your doctor may need to lower your phenobarbital dose and monitor your blood levels closely.
How serious is the interaction between Felbamate and Phenobarbital?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Felbamate and Phenobarbital interact?
Felbamate causes the level of phenobarbital in your blood to rise.
Understanding the Felbamate and Phenobarbital Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Felbamate belongs to the Anticonvulsant class and Phenobarbital belongs to the Anticonvulsant (Barbiturate) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Felbamate causes the level of phenobarbital in your blood to rise. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Felbamate has 16 total documented interactions on file in this dataset, and Phenobarbital has 59. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor may need to lower your phenobarbital dose and monitor your blood levels closely. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Felbamate or Phenobarbital based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.