Abstract: AIM: To determine the effect of CYP2C19 gene polymorphism on plasma concentration at steady state (C_ss) of valproic acid (VPA) in patients with epilepsy.METHODS: CYP2C19 variants (*2 and * 3) in 99 patients were detected using PCR-RFLP method, and 88 of them were further studied to determine the relationship between CYP2C19 polymorphism and plasma concentration of VPA.RESULTS:Studying on the *2 and *3, we found that there were five genotypes of CYP2C19 gene in these subjects, and that their frequencies were: 37. 4% for 681GG-636GG, 42. 4% for 681GA-636GG, 6. 1% for 681GG-636GA, 9. 1% for 681AA-636GG and 5. 1% for 681GA-636GA. The ratio of VPA plasma concentration to dosage was significantly higher in poor metabolizer (681AA-636GG) than in extensive metabolizer (681GG-636GG).CONCLUSION: The data suggest that CYP2C19 polymorphism significantly impacts the metabolism of VPA. The pharmacogenomics is important to rationalize the medication of VPA.

Key words: pharmacogenomics, CYP2C19, valproic acid, epilepsia, PCR-RFLP