Acetylator Phenotypes of Saudi Arabians by a Simplified Caffeine Metabolites Test

The authors examined acetylator phenotypes of 296 Saudi subjects of Arabic origin by measuring the molar concentration ratio of two caffeine metabolites, 5‐acetylamino‐6‐formylamino‐3‐methyluracil (AFMU) and 1‐methylxanthine (1MX), using a simplified version of a previously reported high‐performance liquid chromatographic method. Spot urine samples were collected from the subjects who regularly drink coffee, tea, or other caffeinated beverages. The subjects were originally from different regions of Saudi Arabia but currently live primarily in the capital city of Riyadh. The day‐to‐day reproducibility of the molar concentration ratio of AFMU/1MX was established in 14 randomly selected subjects. These metabolites were stable in urine at 4° and −20°, but AFMU was unstable at room temperature (23°). The frequency distribution data indicate that 72.3% of the subjects are of slow acetylator phenotype.