frequencies of two cyp2c19 defective alleles (cyp2c19*2, and *3) among iranian population in mazandaran province

background: cytochrome p450 2c19 (cyp2c19) is a polymorphically expressed enzyme that shows marked interindividual and interethnic variation. cyp2c19*2 and cyp2c19*3 are the most frequently identified defective alleles in orientals and caucasian poor metabolizers (pm). the aim of this study was to investigate the frequencies of cyp2c19*1, cyp2c19*2 and cyp2c19*3 alleles and cyp2c19 genotypes in the mazandarani ethnic group among iranian population.  materials and methods: the study was conducted in 103 unrelated healthy volunteers. dna was extracted from leucocytes and analyzed by the pcr-rflp protocol. the pcr product was digested with restriction enzymes (smai and bamh1) and then separated electrophoretically using polyacrylamide gel.. results: of the alleles tested, cyp2c19*1, and cyp2c19*2, but not cyp2c19*3, were detected. the frequencies for cyp2c19 alleles *1, *2, and *3 were 91%, 9.0%, and 0.0%, respectively. the frequencies of cyp2c19 genotypes *1/*1, *1/*2, *1/*3, *2/*2, *2/*3 and *3/*3 were 84%, 14%, 0.0%, 2.0%, and 0.0%, respectively. conclusion: the result of the present study showed that the two inactive alleles of cyp2c19 accounted for 9.0% of cyp2c19 alleles in our sample versus 8.8 - 40.1% reported in other populations. the frequencies of the studied alleles resulted significant differences between our sample and african and eastern asian populations.