Evidence for polymorphic oxidation of sparteine in Japanese subjects.

The metabolism of sparteine which exhibits a genetic polymorphism in Caucasians was studied in 84 unrelated Japanese subjects. In contrast to a recent study where debrisoquine was used as a probe and no poor metabolizers could be observed in Japanese involving 100 subjects, two subjects had a urinary metabolic ratio of sparteine greater than 20 and thus were poor metabolizers of sparteine. The incidence of poor metabolizer phenotype of sparteine oxidation of 2% seems to be lower in Japanese as compared with various Caucasian populations where 5 to 10% are poor metabolizers of sparteine. However, this is not conclusive, because the 95% confidence interval of the observed frequency, 0.6 to 8%, covers the range reported in the literature for Caucasians.