glutathione extracellular is unable to cross the cell membrane as it is Glutathione-Related Enzymes and Proteins: A
Description
S-acetyl glutathione, a newer form with improved oral bioavailability, falls between liposomal and reduced glutathione in constipation risk

J Am Vet Med Assoc 1986

Trnkova, L

Liebner S, Czupalla CJ, Wolburg H