This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
[{'content': 'The following laxative lowers blood ammonia level in hepatic encephalopathy \nSelect and explain. \nA. Bisacodyl, B. Lactulose, C. Magnesium sulfate, D. Liquid paraffin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lactulose:- It is a semisynthetic disaccharide of fructose and lactose which is neither digested nor absorbed in the small intestine--retains water. Fuher, it is broken down in the colon by bacteria to osmotically more active products. In a dose of 10 g BD taken with plenty of water, it produces soft formed stools in 1-3 days. Flatulence and flatus is common, cramps occur in few. In patients with hepatic encephalopathy, lactulose causes reduction of blood NH3 concentration by 25-50%. The breakdown products of lactulose are acidic--lower the pH of stools. Ammonia produced by bacteria in colon is conveed to ionized NH4 + salts that are not absorbed. Ref:- kd tripathi; pg num:-676', 'role': 'assistant'}]