Poorly absorbed solutes that remain in the intestinal lumen and so create an osmotic gradient into the intestinal lumen, increasing water influx, e.g. magnesium sulphate (Epsom salts) and hydroxide. Unabsorbed carbohydrates such as lactulose and sugar alcohols are substrates for bacterial fermentation and also act as osmotic laxatives. See also disaccharide intolerance.
Subjects: Medicine and Health.