Pharmacology: Pharmacodynamics: Lactulose, a synthetic disaccharide which is the active ingredient of NOPHALAC is metabolized in the colon by the sacchrolytic bacteria producing low molecular weight organic acid mainly lactic acid via bacterial degradation. This lowers the pH of the colon contents with stimulation of peristalsis by promoting the retention of water by an osmotic effect.
In portal systemic encephalopathy (PSE) or (pre)coma hepaticum, the effect has been attributed to 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 alteration of the bacterial nitrogen metabolism by stimulating the bacteria to utilize ammonia for bacterial protein synthesis.
Pharmacokinetics: Lactulose is minimally absorbed after oral administration. It reaches the colon unchanged, where it is metabolized by the colonic bacteria flora. Metabolism is completed at 20-50 g or 40-75 ml; at higher dosages, a proportion may be excreted unchanged.