Which statement is true about lactulose therapy for hepatic encephalopathy?

• A. It decreases ammonia absorption by increasing stool excretion.
• B. It increases ammonia production.
• C. It increases bilirubin excretion.
• D. It decreases gut pH to cause constipation.

Answer: (A)

Lactulose helps treat hepatic encephalopathy by lowering the gut ammonia load. It’s a nonabsorbable sugar that the colon’s bacteria ferment into acids, which lowers the colonic pH. This acidic environment converts absorbed ammonia (NH3) into ammonium (NH4+), a form that is less readily absorbed. At the same time, lactulose acts as a laxative, increasing stool frequency and promoting the elimination of ammonia in the stool. So, reducing ammonia absorption by increasing stool excretion is the best description of its action. It does not raise ammonia production, does not boost bilirubin excretion, and while it lowers gut pH, it does not cause constipation—in fact, it typically causes diarrhea.