Felbamate and Clobazam: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Clobazam
Felbamate
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
Increased serum clobazam and metabolite concentrations
Interaction Deep Dive
There exists a significant increase in clobazam concentrations in patients who receive felbamate, leading to an accumulation of a pharmacologically active clobazam metabolite. The clobazam main metabolite, N-desmethyl-clobazam, has anticonvulsant properties which are nearly comparable to those of the parent drug and may contribute to the therapeutic and adverse effects more than clobazam in chronically treated epileptic patients. The effect of felbamate on clobazam and its metabolite should be kept in mind when signs of toxicity appear in patients receiving antiepileptic polytherapy1.
Why it happens (mechanism)
Inhibition of cytochrome P450 2C19-mediated clobazam metabolism
Literature reports
1 report — tap to read
a) A prospective study was conducted with 66 epileptic children and adults who were receiving chronic clobazam therapy. Group A (n=22) received clobazam monotherapy or clobazam plus an antiepileptic drug (AED) without cytochrome P450 (CYP450) inducing activity, such as valproic acid and/or lamotrigine. Group B (n=28) received clobazam plus AED inducer polytherapy (carbamazepine, phenobarbital, or phenytoin), and/or valproic acid or lamotrigine. Group C (n=16) received clobazam plus felbamate along with an AED inducer, valproic acid, and/or lamotrigine. The metabolite-to-parent drug ratio shifted from 2.8 in group A to 13 and 29 in groups B and C, respectively. The higher clobazam metabolite concentration seen in patients receiving felbamate may be caused by an impairment in the metabolic clearance of clobazam, possibly through inhibition of cytochrome P450 2C19 enzymes 1.
Common questions
Can I take Felbamate and Clobazam together?
Increased serum clobazam and metabolite concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Felbamate and Clobazam interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Felbamate or Clobazam 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)
- Contin M, Riva R, Albani F, et al: Effect of felbamate on clobazam and its metabolite kinetics in patients with epilepsy. Ther Drug Monit 1999; 21:604-608. PubMed
Keep reading about Clobazam
Keep reading about Felbamate
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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