Polymorphisms in ABCB1 and EPHX1 genes influence drug effectiveness in refractory epilepsy: a retrospective study

Aim: Thirty percent of epileptic patients are refractory to treatment. We investigated the association between the number of seizures in refractory epileptic patients and potential interactions between their antiepileptic medications (AEDs) and single nucleotide polymorphisms in genes ABCB1, CYP2C9 and EPHX1. Methods: Thirty-three adult patients were included and tested for genetic variations using the Neuropharmagen (R) test. Retrospective data on AED therapy and number of seizures during the 12 months before inclusion were extracted from clinical records. Results: Patients displaying potential single nucleotide polymorphisms x AED interactions had a median of 14.5 seizures during the previous 12 months (IQR 5.5-105.0), compared to a median of 7.0 seizures (IQR 4.0-12.0) in patients without these interactions (univariate p = 0.051, adjusted p = 0.034). Conclusion: Refractory patients carrying genetic variations potentially affecting their AED medication experienced a significantly higher number of seizures. Thus, genotyping could help to better control epilepsy in some refractory patients.