Source: Health Products Regulatory Authority (IE) Revision Year: 2022 Publisher: Mylan IRE Healthcare Limited, Unit 35/36, Grange Parade, Baldoyle Industrial Estate, Dublin 13, Ireland
Pharmacotherapeutic group: Osmotically acting laxatives
ATC code: A06AD11
In the colon, lactulose is broken down by colonic bacteria into low molecular weight organic acids. These acids lead to a lowering of pH in the colonic lumen and via an osmotic effect to an increase of the volume of the colonic contents. These effects stimulate the peristalsis of the colon and normalise the consistency of the stools. The constipation is cleared and the physiological rhythm of the colon is reinstated.
In hepatic encephalopathy (HE), the effect has been attributed to the suppression of proteolytic bacteria by an increase of acidophilic bacteria (e.g. lactobacillus), trapping of ammonia in the ionic form by acidification of the colonic contents, catharsis due to the low pH in the colon as well as an osmotic effect and the alteration of the bacterial nitrogen metabolism by stimulating the bacteria to utilise ammonia for bacterial protein synthesis. Within this context, however, it should be realised that hyperammonemia alone cannot explain the neuropsychiatric manifestations of HE. The ammonia however might serve as a model compound for other nitrogenous substances.
Lactulose is poorly absorbed after oral administration and reaches the colon unchanged where it is metabolised by the bacterial flora. Metabolism is complete at doses up to 40-75 ml; at higher doses, some may be excreted unchanged.
The results of acute, sub-chronic and chronic toxicity studies in various species indicate that the compound has very low toxicity. The effects observed, appear to be more related to the effect of bulk in gastrointestinal tract than to a more specific toxic activity. In reproduction and teratology experiments in rabbits, rats or mice no adverse effects were found.
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