The role of the liver in the clearance of l-dope from plasma.

The role of the liver in the plasma clearance of l-dopa in the rat was examined. Some published studies which ascribe an important role to the liver in l-dopa clearance are discussed and critically evaluated. Contrary evidence suggesting that the liver is not a significant site of l-dopa clearance in vivo is presented. The plasma concentration of l-dopa during intravenous infusion of the drug was not significantly reduced after a single passage through the liver. All of the data discussed are consistent with the conclusion that the liver plays a minor role in l-dopa clearance in vivo. It is suggested that the small intestine is the major site of metabolism of orally administered l-dopa.