Weber F L, Fresard K M
Gastroenterology. 1981 May;80(5 pt 1):994-8.
In previous studies with cirrhotic subjects administration of oral lactulose caused a reduction in the urea production rate associated with an increase in fecal nitrogen excretion. The change in urea production rate in response to lactulose therapy was an indirect measure of a reduction in total gut ammonia production. In this study, the effect of magnesium sulfate administration was compared with lactulose therapy in 5 cirrhotic subjects to determine whether the effects of lactulose on nitrogen metabolism might be attributed to a nonspecific, cathartic effect. Both magnesium sulfate (5-15 g/day) and lactulose (40-80 g/day) caused significant and comparable increases in stool weight, solids, and total nitrogen. Only lactulose caused a reduction in fecal pH. Magnesium sulfate had no significant effect on the urea production rate or urinary nitrogen excretion, whereas lactulose caused a 25% reduction in the urea production rate and an 18% reduction in urinary nitrogen excretion. The latter was accounted for by a fall in urinary urea. Nitrogen balance was more negative during magnesium sulfate than during control or lactulose periods since magnesium sulfate increased fecal nitrogen without altering urinary nitrogen excretion. These data demonstrated that the effects of lactulose on nitrogen excretion and urea metabolism were not duplicated by equivalent cathartic doses of magnesium sulfate.
在先前针对肝硬化患者的研究中，口服乳果糖会使尿素生成率降低，同时粪便氮排泄增加。乳果糖治疗引起的尿素生成率变化是肠道总氨生成减少的间接指标。在本研究中，对5名肝硬化患者比较了硫酸镁给药与乳果糖治疗的效果，以确定乳果糖对氮代谢的影响是否可能归因于非特异性的导泻作用。硫酸镁（5 - 15克/天）和乳果糖（40 - 80克/天）均显著且同等程度地增加了粪便重量、固体成分和总氮量。只有乳果糖使粪便pH值降低。硫酸镁对尿素生成率或尿氮排泄无显著影响，而乳果糖使尿素生成率降低25%，尿氮排泄降低18%。后者是由于尿尿素减少所致。由于硫酸镁增加了粪便氮而未改变尿氮排泄，因此在硫酸镁治疗期间氮平衡比对照期或乳果糖治疗期更负。这些数据表明，等效导泻剂量的硫酸镁无法复制乳果糖对氮排泄和尿素代谢的影响。
