MEDIUM-CHAIN TRIGLYCERIDES FOR PARENTERAL-NUTRITION - KINETIC PROFILEIN HUMANS

Medium-chain triglycerides (MCTs) have been introduced as lipid substr ates in parenteral nutrition because of their rapid and complete oxida tion. Although there are many clinical studies on the use of MCTs in p arenteral nutrition there are only a few studies on their kinetics; mo st of these studies used indirect methods (such as light scattering) t o determine MCT concentrations in plasma. We determined the hydrolysis rate of MCTs to medium-chain fatty acids (MCFAs) and the disposition rate of MCFAs in nine healthy volunteers who received an intravenous b olus of MCTs as 10% MCT + 10% long-chain triglyceride solution. MCTs a nd MCFAs were analyzed by gas-liquid chromatography. One linear compar tment model was used and its parameters were numerically estimated. Th e first-order transformation constant of the hydrolysis step from MCT to MCFA was 0.0964 +/- 0.0152 min(-1) (for 8- and 10-carbon pooled tog ether); the rate constant for tissue MCFA uptake from plasma was 0.072 5 +/- 0.0230 min(-1). The apparent volumes of distribution were about 4.5 L for MCT and 19 L for MCFA in a typical 70-kg subject. The plasma half-life of MCT was 11 min and that of MCFA was 17 min. The limiting step in the clinical use of MCTs seems to be tissue uptake of MCFAs.