Lactulose, the active ingredient, is a synthetic disaccharide that is metabolized in the colon by saccharolytic bacteria. This process produces organic acids, primarily lactic acid, which lowers the pH of the colon contents, promoting water retention via an osmotic effect and increasing peristalsis.
Lactulose is minimally absorbed, and its principal therapeutic action is in the colon.
Osmolax is a hyperosmolar laxative that works by drawing water into the bowel, causing distention through fluid accumulation, which softens the stool and accelerates bowel movement. It is a non-absorbable disaccharide that does not get absorbed into the bloodstream.