- Design
- Retrospective single-centre cohort using routine therapeutic drug monitoring data
- Population
- 213 patients, 891 serum brivaracetam samples
- Primary outcome
- Serum brivaracetam concentration with vs without cenobamate
- Effect
- +32% at cenobamate 12.5 to 50 mg/day (P=0.001); -21% at 250 to 450 mg/day (P<0.001)
Cenobamate inhibits CYP2C19, which helps metabolise brivaracetam, so an interaction was expected. This retrospective single-centre study analysed routine serum brivaracetam concentrations: 891 samples from 213 patients, comparing those also taking cenobamate (2021 to 2024) with others on brivaracetam alone (2016 to 2017). Generalised estimating equations adjusted for factors such as enzyme-inducing co-medication.
The effect was biphasic. At cenobamate 12.5 to 50 mg a day, brivaracetam concentrations were about 32% higher (P=0.001). At 250 to 450 mg a day, they were about 21% lower (P<0.001). The authors conclude the interaction is dose-dependent and that prospective studies are needed to define its clinical relevance.
The study does not test why the direction changes. It also compares different periods and patient groups, so unmeasured differences may contribute.
- When adding cenobamate to brivaracetam, expect brivaracetam levels to rise at low cenobamate doses.
- At high cenobamate doses (250 to 450 mg a day), expect brivaracetam levels to fall.
- Consider checking brivaracetam concentrations after cenobamate dose changes, where assays are available.
- Review tolerability and seizure control after each cenobamate dose change.
- Do not adjust doses by formula; clinical relevance has not been established.
Why it matters
A single interaction pointing in two directions makes a one-time dose adjustment at the start unreliable.
Don't overread it
A retrospective study of drug concentrations does not show changes in seizure control or adverse effects.
The statistics, in plain English
A 32% rise and a 21% fall refer to average serum concentrations across patients, not to every individual. The comparison group came from an earlier period, so differences other than cenobamate could contribute.
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