Comprehensive analysis of the association of SCN1A gene polymorphisms with the retention rate of carbamazepine following monotherapy for new-onset focal seizures in the Chinese Han population

Summary The aim of the present study was to investigate whether single nucleotide polymorphisms (SNPs) in the sodium channel a subunit type 1 (SCN1A) gene affect the retention rate of carbamazepine (CBZ) used to treat seizures in Chinese Han patients with epilepsy. In total, 448 patients were genotyped for SNPs selected in the SCN1A gene. The tag SNPs were selected using Haploview version 4.2 software (http://www.broad.mit.edu/haploview/haploview, accessed 18 Sept 2009). Monotherapy with CBZ was administered to patients with new-onset focal seizures. In the present study, the retention rate of CBZ was defined as the percentage of patients with epilepsy who had continued with CBZ treatment in the preceding 3 months. Potential confounding variables were analysed to evaluate the risk factors for non-retention. When adjusted for potential confounding factors (e.g. age, sex, body mass index, seizure type etc.), the presence of the A allele of SNP rs3812718 predicted non-retention (P = 0.015; odds ratio (OR) = 3.122; 95% confidence interval (CI) = 1.823–4.893). Beyond 12 months of treatment in those that continued with CBZ (retention cohort), analysis of covariance indicated that the maintenance dose (P = 0.025) and serum CBZ levels (P = 0.021) were significantly higher in carriers of the rs3812718 AA genotype than in those with the GG genotype. The results of the present study indicate that the rs3812718 SNP in the SCN1A gene is significantly associated with the retention rate of CBZ monotherapy in Chinese Han patients with focal epilepsy.