Ammonia absorption in colon

Ammonia absorption in the colon refers to the movement of ammonia from the lumen of the colon across the epithelial barrier into the systemic circulation[5][3]. This process depends on the form of ammonia present; nonionic NH₃ can diffuse passively, while NH₄⁺ (ammonium ion) is less readily absorbed[5][3][4]. Colonic acidification, such as that induced by lactulose therapy, promotes formation of NH₄⁺, limiting ammonia absorption and lowering plasma ammonia—an effect exploited therapeutically to reduce complications of liver disease, notably hepatic encephalopathy[1][4]. This entity is best categorized as a physiological process with important pathophysiological and therapeutic implications, rather than a molecular target. Thus, it does not conform to the typical structure of druggable targets such as receptors, enzymes, or transporters.

Other names

Ammonia uptake in colonColonic ammonia absorption

Lactulose acidifies the colonic contents, trapping ammonia as non-absorbable ammonium ion (NH₄⁺), thereby reducing ammonia absorption[1][4]. Rifaximin alters colonic microbiota, decreasing ammoniagenesis.