[The significance of cysteine and its derivatives in parenteral nutrition].

Data on l-cysteine (CYS) concentrations obtained by automated amino acid analysis are in fact cystine measurements. The necessity of a uniform use of nomenclature is discussed. The importance of a CYS supply during parenteral nutrition (PN) is pointed out by several studies. The presently available CYS derivatives and their potential use as CYS source in PN are discussed.