Phenotype-genotype analysis of CYP2C19 in Colombian mestizo individuals

189 subjects were genotyped using the multiplex SNaPshot technique and a subgroup of 44 individuals received 20 mg of omeprazole followed by blood collection at 3 hours to determine the omeprazole hydroxylation index by HPLC.83.6%, 15.3% and 1.1% of the subjects were genotyped as EMs, IMs and PMs, respectively. The frequencies of the CYP2C29*1 and CYP2C19*2 alleles were 91.3% and 8.7% respectively whereas the *3, *4, *5, *6 and *8 alleles were not found. No discrepancies were found between the genotype and phenotype of CYP2C19.The frequency of poor metabolizers (1.1%) in the Colombian mestizos included in this study is similar to that in Bolivian mestizos (1%) but lower than in Mexican-Americans (3.2%), West Mexicans (6%), Caucasians (5%) and African Americans (5.4%). The results of this study will be useful for drug dosage recommendations in Colombian mestizos.The CYP2C19 isoenzyme, a member of the superfamily of xenobiotic enzymes of cytochrome P-450, is responsible for the metabolism of several therapeutically important drugs, such as proton-pump inhibitors (omeprazole, lansoprazole, pantoprazole), antidepressants (citalopram, imipramine), benzodiazepines (diazepam, flunitrazepam), propranolol and proguanil [1-3].The CYP2C19 gene polymorphism divides populations in three phenotypic subgroups: extensive metabolizers (EMs), intermediate metabolizers (IMs), and poor metabolizers (PMs). The enzymatic deficiency is inherited as an autosomal recessive trait [4].The frequencies and types of alleles vary between ethnic groups. Thus, 13 to 23% of Orientals are PMs and the CYP2C19*2 and *3 alleles account for 99% of them in this ethnic group [5], whereas in Caucasians, with a percentage of PMs near to 5% of the population, only the *2 allele is common although other variants have been described [6-9]. In Black population some new mutations (*9, *10, *12) have been reported and the frequency of PMs individuals is 5.4% [10,11]. The clinical consequences of the CYP2C19 gene p