In cirrhosis with hepatic encephalopathy, which therapy is used to reduce ammonia levels?

• A. Rifaximin
• B. Lactulose
• C. Metronidazole
• D. Neomycin

Answer: (B)

Lactulose lowers ammonia levels by changing what happens in the gut. In cirrhosis, ammonia from gut bacteria can accumulate and contribute to hepatic encephalopathy. Lactulose is a nonabsorbable sugar that gets fermented in the colon to acids, which acidify the colonic lumen. This shift converts ammonia (NH3) into ammonium (NH4+), a form that is not readily absorbed, so more ammonia is trapped in the gut and excreted in stool. In addition, its osmotic laxative effect speeds intestinal transit, reducing the time available for ammonia production and absorption. This combination directly reduces blood ammonia and improves encephalopathy. Rifaximin can be added to further reduce ammonia-producing bacteria, but lactulose is the primary therapy.