The major site of ammonia production of the body is the gastrointestinal tract.1-3 Protein substances are broken down by bacterial enzymes to ammonia, which is normally carried by portal blood to the liver for detoxification. In patients with cirrhosis of the liver and portal hypertension portal-systemic shunts may be present, permitting ammoniarich portal blood to bypass the liver and reach the systemic circulation.4 Ammonia intoxication or hepatic encephalopathy may result.
A wide variety of therapeutic measures have been directed toward control of ammonia production. Neomycin has been used to depress the intestinal bacterial flora, thereby preventing ammonia formation.5,6 Another approach has been the use of enzyme inhibitors to limit the breakdown of proteins to ammonia. The two major enzyme systems involved in ammonia formation within the gut are amine-oxidase and urease. Recent experiments have shown that amine-oxidase inhibitors are effective in controlling levels of blood ammonia in