DIFFERENCE OF THE PLASMA-CONCENTRATION AND URINARY-EXCRETION OF ALLOPURINOL, OXYPURINOL, AND PURINE-BASES BETWEEN DIETARY-INTAKE AND FASTING

To investigate how much the metabolism of allopurinol, oxypurinol, and purine bases during dietary intake (total calorie 2,083 kcal, total p rotein 107.5 g, total lipid 74.1 g, total carbohydrate 228.3 g, total purine 180.5 mg) differs from that during fast, allopurinol (300 mg) w as administered to 5 normal subjects after a 6-hour fast and then brea kfast was taken. Four and 10 hours after the administration of allopur inol lunch and dinner were taken, respectively. Two weeks later the sa me protocol was performed, except for the intake of only water instead of diet. The fractional clearances and urinary excretions of oxypurin ol, uric acid, and the clearance of creatinine were increased by dieta ry intake, compared with the respective ones resulting from fasting. A t the same time the plasma concentrations of hypoxanthine, xanthine, a nd oxypurinol were decreased in dietary intake, compared with the resp ective ones in fasting, while the urinary excretion of neither allopur inol, hypoxanthine, nor xanthine was affected. These results suggest t hat the administration of allopurinol at bed time (during the nocturna l fast) may be more effective than that after breakfast in order to de crease the plasma concentration of uric acid.