Pharmacokinetic and Pharmacodynamic Properties of l-Ornithine l-Aspartate (LOLA) in Hepatic Encephalopathy

l-Ornithine l-aspartate (LOLA), a stable salt of l-ornithine and l-aspartate, readily dissociates into its constituent amino acids that are readily absorbed by active transport, distributed, and metabolized. l-ornithine serves as an intermediary in the urea cycle in periportal hepatocytes in the liver and as an activator of carbamoyl phosphate synthetase, and, like l-aspartate, by transamination to glutamate via glutamine synthetase in perivenous hepatocytes as well as by skeletal muscle and brain. By way of these metabolic pathways, both amino acids participate in reactions whereby the ammonia molecule is incorporated into urea and glutamine and it is the nature, cellular, and biological location of these pathways that underpins the application of LOLA as an effective ammonia-lowering strategy widely used for the management and treatment of hepatic encephalopathy. These metabolic pathways were elucidated based upon studies in experimental animals and were confirmed by studies in patients with severe liver diseases. More recent studies suggest that LOLA may have additional direct hepatoprotective properties. Moreover, its use may result in improvements in skeletal muscle function in cirrhosis.