Glutathione

Glutathione IS a peptide, which is why it belongs in this library rather than sitting awkwardly in it: it is a TRIPEPTIDE of glutamate, cysteine and glycine (gamma-Glu-Cys-Gly), built inside cells rather than synthesised on a peptide bench. The gamma linkage between the glutamate side chain and cysteine is unusual and is what protects it from ordinary peptidases. It is the body's principal intracellular antioxidant and a substrate for glutathione-S-transferase detoxification.

ORAL BIOAVAILABILITY IS POOR, AND THIS IS THE CENTRAL PRACTICAL FACT ABOUT IT. Swallowed glutathione is largely hydrolysed by intestinal and hepatic gamma-glutamyltransferase back into its constituent amino acids before it reaches the circulation, so much of what an oral dose achieves it achieves by supplying cysteine, which is the rate-limiting precursor for the body to make its own. Trials of oral glutathione on circulating glutathione status have been mixed, with some showing no change in blood markers at all; N-acetylcysteine is the better-studied oral way to raise glutathione.

MOST OF THE HUMAN EVIDENCE CONCERNS IV OR INHALED ROUTES, not oral and not subcutaneous. The controlled work includes intravenous glutathione in Parkinson's disease, intravenous and intra-arterial use in oncology supportive care for platinum neuropathy, and nebulized glutathione in cystic fibrosis and other lung disease; an intranasal reduced-glutathione formulation has also been through early-phase Parkinson's trials.

Intravenous doses in that literature typically run 600-2400 mg per infusion. There is no IV route in this dataset, so subq is listed and the IV figures live here instead — they are NOT interchangeable with subcutaneous or oral dosing. The 100 mg to 2 g range above spans all of those routes; 600 mg is a typical single parenteral dose. Frequency is stored as daily because that is how oral and sublingual products are taken; parenteral use in clinics is more often one to three times a week.

Skin-lightening is the most commonly marketed use and the least well supported: the trials are small, short and mostly in one region, and high-dose IV glutathione for cosmetic lightening has drawn safety warnings from national regulators. Plasma glutathione is cleared within minutes, so no meaningful half-life is listed. Reconstitution fields are omitted deliberately: it is supplied as a ready-made solution, a capsule or a sublingual preparation far more often than as a lyophilized vial you make up yourself, and in solution the reduced form oxidises, so any made-up product has a short working life.