Disaccharide, synthetic

Lactulose. 4-O-P -D-Galactopyranosyl-4-D-fmctofuranose [4618-18-2] (Chronolac) (12) may be made from lactose using the method described in Reference 9. It is a synthetic disaccharide that is not hydroly2ed by gastrointestinal enzymes in the small intestine, but is metabolized by colonic bacteria to short-chain organic acids. The increased osmotic pressure of these nonabsorbable organic acids results in an accumulation of fluid in the colon. Lactulose may not be tolerated by patients because of an extremely sweet taste. It frequently produces flatulence and intestinal cramps. 

Figure 10.31 Synthetic route to oxygenated pyrrolizidine alkaloids, and an aza-C-disaccharide as glycosidase inhibitors.

Lactulose is the foundation of pharmacologic therapy to prevent and treat hepatic encephalopathy. It is a non-digestible synthetic disaccharide laxative that is hydrolyzed in the gut to an osmotically-active compound that draws water into the colon and stimulates defecation. Lactulose also lowers colonic pH, which favors the conversion of ammonia (NH3) to ammonium (NHf).48 Ammonium is ionic and cannot cross back into systemic circulation it is eliminated in the feces. Lactulose is usually initiated at 15 to 30 mL two to three times per day and titrated to a therapeutic goal of two to four soft bowel movements daily.20 49 50... 

Figure 13.17.1 The molecular structure of sucrose, a disaccharide of glucose and fructose. Asterisks indicate the hydroxyl groups replaced with chlorine atoms in the synthetic sweetner.

D-Galactosido-D-glucosone and D-glucosido-D-galactosone were prepared by Fischer and Armstrong203 by the action of benzaldehyde on the osazones of synthetic disaccharides. Both osones were hydrolyzed by emulsin. There is some doubt as to the precise structure of the parent sugars.206... 

L The answer is a. (Hardman, p 922) Lactulose is a synthetic disaccharide (galactose-fructose) that is not absorbed. In moderate doses, it acts as a laxative. In higher doses, it is capable of binding ammonia and other toxins that form in the intestine in severe liver deficiency and that are believed to cause the encephalopathy. Loperamide is an antidiarrheal opioid lorazepam is a CNS depressant loxapine is a heterocyclic antipsychotic. 

Like the other synthetic disaccharides, it gives the Raybin reaction, which indicates that the local structure about the glycosidic linkage in the glucosyl-sorboside is the same as that of sucrose. 

Duphalac is a proprietary preparation of lactulose, an osmotic laxative. Lactulose, which is a semi-synthetic disaccharide, is not absorbed from the gastrointestinal tract and produces an osmotic diarrhoea of low faecal pH, which discourages the proliferation of ammonia-producing organisms. 

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