Variability in caffeine metabolism

Abstract
Urinary metabolites excreted after oral caffeine were quantified in a healthy sample (n = 68) by HPLC [high performance liquid chromatography] analyses. The profile of metabolites, assessed by examining particular metabolite ratios, differed widely among subjects. Ratios denoting cytochrome P-450-dependent activities were interethnically variable between Oriental and Caucasian groups, whereas those indicative of xanthine oxidase activity exhibited neither significant interindividual variation nor an ethnic difference. A ratio providing an index of polymorphic N-acetyltransferase activity holds promise as a simple marker for acetylator status in man.