Which laxative works by retaining water in the intestinal lumen through osmotic action and is safe for use in hepatic encephalopathy?

• A Bisacodyl
• B Lactulose ✓
• C Liquid paraffin
• D Senna

Explanation

Lactulose is a synthetic disaccharide not absorbed from the GI tract; colonic bacteria ferment it to organic acids (lactic, acetic, formic), which lower colonic pH and create an osmotic load retaining water and softening stools. In hepatic encephalopathy, the acidic environment converts ammonia (NH3) to ammonium ion (NH4+) which is non-absorbable, and the cathartic effect reduces intestinal transit time for ammonia generation — thereby lowering serum ammonia levels.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.