Figure 1: Caffeine biotransformation pathway. Caffeine metabolism is largely dependent on the cytochromes P450 in the adult. However, these enzymes are not fully developed in the infant and young child. CYP1A2 indicates cytochrome P4501A2; CYP2A6, cytochrome P4502A6; XO, xanthine oxidase; NAT-2, N-acetyltransferase 2; 1X, methylxanthine; 7X, 7-methylxanthine; 17X, 1,7-dimethylxanthine, 1U, 1-methyluric acid; AMFU, 5-acetylamino-6- formylamino-3-methyluracil; 17U; 1,7- dimethyluric acid; 7U, 7-methyluric acid; AAMU, 5-acetylamino-6-amino-3-methyluracil.