Lactulose is a synthetic disaccharide sugar that acts as an osmotic laxative and ammonia-detoxifying agent. It passes completely undigested through the upper GI tract into the colon, where indigenous colonic bacteria ferment it into low-molecular-weight organic acids (like lactic and acetic acids). This fermentation process increases osmotic pressure in the bowel, drawing in water to soften stool and stimulate natural peristalsis. Additionally, the resulting acidic environment converts diffusible toxic ammonia into non-absorbable ammonium ions trapping it in the colon for safe excretion.