Effective lowering of circulating ammonia is the mainstay strategy in the prevention and treatment of hepatic encephalopathy in cirrhosis and there is increasing interest in agents with the metabolic potential for the active removal of ammonia by the liver and skeletal muscle by agents including l-ornithine l-aspartate, branched-chain amino acids, as well as the re-purposing of benzoate and phenylacetate currently employed for the control of hyperammonaemia in congenital urea-cycle enzymopathies. Based upon results of multiple systematic reviews with meta-analyses, l-ornithine l-aspartate demonstrably lowers circulating ammonia in patients with cirrhosis with concomitantly improved mental status. Distinct mechanisms responsible include optimisation of hepatic metabolic pathways for ammonia removal as well as direct hepatoprotective effects involving the release of glutathione and of nitric oxide with beneficial effects on hepatic microcirculation. l-ornithine l-aspartate also prevents cirrhosis-related sarcopenia, leading to increased capacity for ammonia removal by skeletal muscle. Branched-chain amino acids continue to be prescribed as nutritional supplements with the potential to result in improvements in liver function. Sodium benzoate, glycerol phenylbutyrate and an analogous compound l-ornithine phenylacetate were also evaluated. Glycerol phenylbutyrate was the only agent with a beneficial effect on both hyperammonaemia and hepatic encephalopathy. None were superior to lactulose for the lowering of blood ammonia.

有效降低循环氨是在预防和治疗肝性脑病的肝硬化为主的策略并没有与由肝脏和骨骼肌通过代理活动除氨代谢潜在因素越来越多的关注，包括升鸟氨酸升-天冬氨酸、支链氨基酸，以及重新利用目前用于控制先天性尿素循环酶病中的高氨血症的苯甲酸盐和苯乙酸盐。根据多项系统评价和荟萃分析的结果，l-鸟氨酸l-天冬氨酸可明显降低伴随精神状态改善的肝硬化患者的循环氨。负责的不同机制包括优化肝脏代谢途径以去除氨以及直接保肝作用，包括释放谷胱甘肽和一氧化氮，对肝脏微循环产生有益影响。l -鸟氨酸l -天冬氨酸还可以预防肝硬化相关的肌肉减少症，从而增加骨骼肌去除氨的能力。支链氨基酸继续被用作营养补充剂，具有改善肝功能的潜力。苯甲酸钠、甘油苯基丁酸酯和类似化合物l还评估了-鸟氨酸苯乙酸盐。甘油苯基丁酸酯是唯一对高氨血症和肝性脑病均具有有益作用的药物。在降低血氨方面，没有一种优于乳果糖。