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.
In contrast, Jennifer Cohn of Doctors Without Borders and the organization Doctors of the World criticized the price of sofosbuvir as reflecting "corporate greed" and ignoring the needs of people in developing countries.In Algeria, as of 2011 about 70,000 people were infected with hepatitis C. As of August 2015, Gilead had licensed its partners in India to sell sofosbuvir in Algeria. It had been criticized for not making the drug available in middle-income countries including Algeria prior to that. Controversies
The price has generated considerable controversy. In 2017, the range of costs per treatment varied from about $84,000 to about $50. Patent challenges
In February 2015, it was reported that Doctors of the World had submitted an objection to Gileads patent at the European Patent Office, claiming that the structure of sofosbuvir is based on already known molecules. In particular, Doctors of the World argued that the Protide technology powering sofosbuvir was previously invented by the Chris McGuigan team at Cardiff University in the UK, and that the Gilead drug is not therefore inventive. The group filed challenges in other developing countries as well. These challenges were unsuccessful and the court recognized the innovative step in pro-drug design and application to the specific example of sofosbuvir. Medical tourism
Due to the high cost of sofosbuvir in the U.S., as of 2016 increasing numbers of Americans with hepatitis C were traveling to India to purchase the drug.