title: Effects of allopurinol on theophylline metabolism and clearance.
abstract: The effects of allopurinol on the plasma clearance and metabolism of theophylline in man were investigated under single-dose and multiple-dosing conditions. No change in theophylline clearance was found with the concomitant use of allopurinol but 1-methylxanthine (1MX), a theophylline metabolite not previously described in man, was detected in urine during control and allopurinol treatment phases under both single- and multiple-dosing conditions. 1MX excretion increased at the expense of 1-methyluric acid (1MU) during the allopurinol treatment phase. It is proposed that the secondary biotransformation of 1MX to 1MU is mediated by xanthine oxidase.
mesh_terms: D000328:Adult; D000493:Allopurinol; D004334:Drug Administration Schedule; D006801:Humans; D007700:Kinetics; D008297:Male; D012907:Smoking; D013806:Theophylline / Q000097:blood / Q000378:metabolism* / Q000652:urine; D014970:Xanthines / Q000652:urine
chemical_list: D014970:Xanthines; D000493:Allopurinol; D013806:Theophylline