The systemic availability of oral glutathione.

When the plasma glutathione concentration is low, such as in patients with HIV infection, alcoholics, and patients with cirrhosis, increasing the availability of circulating glutathione by oral administration might be of therapeutic benefit. To assess the feasibility of supplementing oral glutathione we have determined the systemic availability of glutathione in 7 healthy volunteers. The basal concentrations of glutathione, cysteine, and glutamate in plasma were 6.2, 8.3, and 54 mumol.l-1 respectively. During the 270 min after the administration of glutathione in a dose of 0.15 mmol.kg-1 the concentrations of glutathione, cysteine, and glutamate in plasma did not increase significantly, suggesting that the systemic availability of glutathione is negligible in man. Because of hydrolysis of glutathione by intestinal and hepatic gamma-glutamyltransferase, dietary glutathione is not a major determinant of circulating glutathione, and it is not possible to increase circulating glutathione to a clinically beneficial extent by the oral administration of a single dose of 3 g of glutathione.