The natural αCD and βCD, unlike γCD, cannot be hydrolyzed by human salivary and pancreatic amylases. However, both α- and β-cyclodextrin can be fermented by the intestinal microflora. Cyclodextrins are both large (MW ranging from almost 1000 to over 2000 Daltons) and hydrophilic with a significant number of H-donors and acceptors and, thus, are poorly absorbed from the gastrointestinal tract in their intact form. Hydrophilic cyclodextrins are considered non-toxic at low to moderate oral dosages. Lipophilic cyclodextrin derivatives, such as the methylated cyclodextrins, are to some extent absorbed from the gastrointestinal tract in to the systemic circulation and have been shown to be toxic after parenteral administration. The natural αCD and βCD, unlike γCD, cannot be hydrolyzed by human salivary and pancreatic amylases. However, both αCD and βCD can be fermented by the intestinal microflora. βCD can not be given parenterally due to its low aqueous solubility and adverse effects (e.g. nephrotoxicity). The metabolism of γCD closely resembles that of starch and linear dextrins. Oral administration of 8 g γCD or 8 g maltodextrin to humans did not reveal any differences in gastrointestinal tolerance of these two oligosaccharides. The biological half-life of HPβCD and SBEβCD in humans after intravenous injection is about 1.7 h and its apparent volume of distribution (VD) is 0.2 l/kg. After intravenous injection HPβCD and SBEβCD are almost exclusively eliminated unchanged through the kidneys via glomerular filtration.