Limited frequency of the CYP2C19*17 allele and its minor role in a Japanese population.

AIMS We investigated the CYP2C19*17 allelic frequency in Japanese subjects, and evaluated whether CYP2C19*17 is an important determinant of interindividual variability of CYP2C19 activity. METHODS We enrolled 265 subjects to determine their CYP2C19 genotype and plasma metabolic ratio following a single dose of 40 mg omeprazole. RESULTS Seven subjects heterozygous for CYP2C19*17 and no *17/*17 subjects resulted in the CYP2C19*17 frequency being 1.3%. These heterozygotes had moderate metabolic activities when compared with the metabolic ratio of the other subjects. CONCLUSIONS The low frequency of CYP2C19*17 and the absence of *17/*17 indicates that CYP2C19*17 plays a minor role in the Japanese population.