The lack of influence of IVS5-91 G>A polymorphism of the SCN1A gene on efficacy of lamotrigine in patients with focal epilepsy.

Background: IVS5-91G>A (rs3812718) polymorphism of the sodium voltage-gated channel alpha subunit 1 (SCN1A) gene has been associated with inadequate responsiveness to common antiepileptic drugs which act as sodium channel blockers. This study was performed to investigate the effect of IVS5-91G>A (rs3812718) polymorphism on lamotrigine (LTG) efficacy in a cohort of patients with non-lesional focal epilepsy taking LTG as monotherapy. Methods: A total of 100 of patients with non-lesional focal epilepsy on LTG monotherapy was included in this prospective interventional study. After reaching a stable dose of LTG patients were followed-up for 12 consecutive months. LTG responsiveness was defined as a 75% or more reduction in seizure frequency on a stable dose of LTG. Genotyping was performed at the end of the study using standard procedures and data were correlated with clinical data. Results: There were no significant differences in the prevalence of responsiveness to LTG between carriers of different genotypes. Average maintenance LTG doses in the responder group differed by genotype in the order AA>GA>GG, but these differences did not reach statistical significance. Conclusion: Our data suggest lack of association between SCN1A IVS5-91G>A (rs3812718) polymorphism and response to LTG.