Mechanism of action
It is a disaccharide formed from one molecule each of the simple sugars (monosaccharides) fructose and galactose. Lactulose is not normally present in raw milk, but is a product of heat processes: the greater the heat, the greater amount of this substance (from 3.5 mg/L in low-temperature pasteurized milk to 744 mg/L in in-container sterilized milk). It is produced commercially by isomerization of lactose.Lactulose is not absorbed in the small intestine nor broken down by human enzymes, thus stays in the digestive bolus through most of its course, causing retention of water through osmosis leading to softer, easier-to-pass stool. It has a secondary laxative effect in the colon, where it is fermented by the gut flora, producing metabolites which have osmotic powers and peristalsis-stimulating effects (such as acetate), but also methane associated with flatulence.Lactulose is metabolized in the colon by bacterial flora into short-chain fatty acids, including lactic acid and acetic acid. These partially dissociate, acidifying the colonic contents (increasing the H+ concentration in the gut). This favors the formation of the nonabsorbable NH+4 from NH3, trapping NH3 in the colon and effectively reducing plasma NH3 concentrations. Lactulose is therefore effective in treating hepatic encephalopathy. Specifically, it is effective as secondary prevention of hepatic encephalopathy in people with cirrhosis. Moreover, research showed improved cognitive functions and health-related quality of life in people with cirrhosis with minimal hepatic encephalopathy treated with lactulose. Society and culture
Name
Lactulose  is its international nonproprietary name (INN). It is sold under various brand names.
Availability
Lactulose is available as a generic medication. It is available without prescription in most countries, but a prescription is required in the United States and Austria. Food additive
In some countries where lactulose may be obtained without a prescription, lactulose is commonly used as a food additive to improve taste and promote intestinal transit. Veterinary use
Lactulose is used in veterinary medicine. References
External links

"Lactulose". Drug Information Portal. U.S. National Library of Medicine.