Lactulose: A Simple Sugar in a Complex Encephalopathy.

Hepatic encephalopathy is a common encephalopathy and one of the very few that are treatable. Lactulose has remained a standard pharmaceutical intervention and is listed as one of the World Health Organization's Essential Medicines. The discovery of lactulose, the acid dialysis proof of concept, and the role of Bircher are not well known. This historical vignette reviews the gradual understanding of the complex liver-brain connection, the effective treatment of hepatic stupor with lactulose, and the immediate relevance of lactulose to the practice of consultative neurocritical care.