Which medications are used to lower blood ammonia in hepatic encephalopathy?

• A. Lactulose and rifaximin
• B. Metformin and insulin
• C. Antacids
• D. Vitamin K

Answer: (A)

Lowering ammonia levels from the gut is central to treating hepatic encephalopathy. Lactulose works by acidifying the colon, which converts ammonia (NH3) to ammonium (NH4+). Ammonium is less readily absorbed, so it stays in the gut and is excreted, and the laxative effect also reduces the time for ammonia production. Rifaximin is a nonabsorbable antibiotic that lowers the amount of ammonia produced by gut bacteria, further reducing systemic ammonia levels. Together, they directly target the mechanism driving encephalopathy and improve mental status; lactulose is typically first-line, with rifaximin added for recurrent or more severe cases.

Metformin and insulin address glucose control, not ammonia. Antacids don’t meaningfully lower ammonia levels, and vitamin K corrects coagulation defects related to liver disease but not ammonia.