The age-dependence of intestinal absorption using d-xylose as an example.
In 40 infants the serum concentrations of D-xylose were measured from capillary blood samples up to 300 min after an oral dosage of 0.5 g of D-xylose per kg body weight. The parameters of the absorption kinetics, which are calculated by a digital computer program, showed an age-dependent behavior. Infants up to the age of 2 months have lower maximal serum concentrations compared to older ones because of a larger volume of distribution. The rate constant of invasion k1, which serves as a measure for the rate of intestinal absorption and the rate constant of elimination k2 were significantly lower in infants up to the age of 2 months compared to older ones. The quotient of k1:k2 was independent of age. The time it took to reach maximal serum concentration was significantly longer in young infants. By adding metoclopramide simultanously to the oral D-xylose doses it could be demonstrated that the slower motility of the gastrointestinal tract in newborns and young infants is not exclusively responsible for the slower rate of absorption of D-xylose. Comparing the absorption rates in 26 infants after different D-xylose dosages a saturation kinetics may be supposed.
D000367:Age Factors; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007408:Intestinal Absorption / Q000187:drug effects; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D013997:Time Factors; D014994:Xylose / Q000097:blood / Q000378:metabolism*
D014994:Xylose; D008787:Metoclopramide