Kinetic analysis of D-xylose absorption in normal subjects and in patients with chronic renal failure.

D-Xylose kinetics were studied in 12 normal subjects and in nine patients with chronic renal failure requiring dialysis (five hemodialysis and four peritoneal dialysis). None of the study subjects had demonstrable gastrointestinal disease. Doses of D-xylose were given intravenously (10 gm) and orally (25 gm) on different nondialysis days in order to determine the distribution and elimination kinetics and the absolute bioavailability of this compound. Our findings were as follows. (1) The nonrenal clearance of D-xylose is markedly reduced in chronic renal failure patients (43.3 vs. 90.9 ml/min, p less than 0.002). (2) D-Xylose is less completely absorbed in patients with chronic renal failure than in normal subjects (48.6% vs. 69.4%, p less than 0.01). (3) The absorption rate of D-xylose is slower in these patients than in normal subjects (0.555 hr-1 vs. 1.03 hr-1, p less than 0.05). (4) The absorption rate is positively correlated with the extent of D-xylose absorption (r = 0.49, p = 0.03). (5) Although peak D-xylose concentrations measured 1 hr after oral administration are well correlated with the extent of D-xylose absorption in normal subjects and in functionally anephric patients (r = 0.59, p less than 0.01), formal kinetic study is required to determine D-xylose bioavailability precisely because of the large variability in peak serum D-xylose concentrations and in the time required to reach these peak concentrations.