RESUMEN
An association between a polymorphism of the SCN1 gene, a therapeutical target of lamotrigine, and an effective dose (a blood plasma concentration) of the drug in patients with epilepsy has been studied. Fifty patients with different forms of epilepsy have been genotyped for the SCN1 IVS5N+5 G>A polymorphism using polymerase chain reaction. The distribution of allelic variants was as follows: 23 patients had the mutant homozygous genotype (V/V), 20 - the heterozygous genotype Wt/V and 7 were homozygous for the wild allele (Wt/Wt). Mean lamotrigine doses were 85,7+/-7,4 mg/day for carriers of the Wt/Wt genotype, 113,75+/-7,13 mg/day for the Wt/V genotype and 142,4+/-15,43 mg/day for the V/V genotype. Peak plasma concentrations corresponded to effective doses were 0,6+/-0,065 mg/ml for Wt/Wt, 0,96+/-0,1 mg/ml for V/V and 0,72+/-0,1 mg/ml for Wt/V. The hypothesis on the association between the SCN1 IVS5N+5 G>A polymorphism and the effective dose (concentration) of lamotrigine was confirmed. The significantly higher frequency of the SCN1A mutation in the group of patients with epilepsy compared to the control group of Caucasians (45,5 and 21,3%, respectively) implies that this polymorphism may contribute to the pathogenesis of epilepsy.