RT Journal Article SR Electronic T1 Theobromine metabolism in man. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 672 OP 675 VO 10 IS 6 A1 J O Miners A1 J Attwood A1 D J Birkett YR 1982 UL http://dmd.aspetjournals.org/content/10/6/672.abstract AB The effects of allopurinol on the plasma clearance and metabolism of theobromine have been investigated under multiple-dosing conditions. Allopurinol had no effect on the clearance of theobromine, indicating that the elimination of this compound is dependent on enzyme systems other than xanthine oxidase, presumably the hepatic mixed-function oxidases. The excretion of 3-methylxanthine, 6-amino-5-(N-methylformylamino)-1-methyluracil, and unchanged theobromine were similarly unaffected by the allopurinol treatment. Although allopurinol abolished the formation of 7-methyluric acid (7MU) and increased the excretion of 7-methylxanthine (7MX), the metabolic clearance to (7MX + 7MU) was not significantly different with and without allopurinol. It is proposed that the secondary biotransformation of 7MX to 7MU is mediated by xanthine oxidase.