TAILIEUCHUNG - Color Atlas of Pharmacology (Part 16): Laxatives and Purgatives

Laxatives and Purgatives colon bacteria to the active free aglycones. Diphenolmethane derivatives (p. 177) were developed from phenolphthalein, an accidentally discovered laxative, use of which had been noted to result in rare but severe allergic reactions. Bisacodyl and sodium picosulfate are converted by gut bacteria into the active colonirritant principle. Given by the enteral route, bisacodyl is subject to hydrolysis of acetyl residues, absorption, conjugation in liver to glucuronic acid (or also to sulfate, p. 38), and biliary secretion into the duodenum. Oral administration is followed after approx. 6 to 8 h by discharge of soft formed stool. When given. | 174 Laxatives and Purgatives Small Bowel Irritant Purgative Ricinoleic Acid Castor oil comes from Ricinus communis castor plants Fig sprig panicle seed it is obtained from the first coldpressing of the seed shown in natural size . Oral administration of 10-30 mL of castor oil is followed within to 3 h by discharge of a watery stool. Ricinoleic acid but not the oil itself is active. It arises as a result of the regular processes involved in fat digestion the duodenal mucosa releases the enterohormone cholecystokinin pancreozymin into the blood. The hormone elicits contraction of the gallbladder and discharge of bile acids via the bile duct as well as release of lipase from the pancreas intestinal peristalsis is also stimulated . Because of its massive effect castor oil is hardly suitable for the treatment of ordinary constipation. It can be employed after oral ingestion of a toxin in order to hasten elimination and to reduce absorption of toxin from the gut. Castor oil is not indicated after the ingestion of lipophilic toxins likely to depend on bile acids for their absorption. Large Bowel Irritant Purgatives p. 177 ff Anthraquinone derivatives p. 176 are of plant origin. They occur in the leaves folia sennae or fruits fructus sennae of the senna plant the bark of Rhamnus frangulae and Rh. purshiana cortex frangulae cascara sagrada the roots of rhubarb rhizoma rhei or the leaf extract from Aloe species p. 176 . The structural features of anthraquinone derivatives are illustrated by the prototype structure depicted on p. 177. Among other substituents the anthraquinone nucleus contains hydroxyl groups one of which is bound to a sugar glucose rhamnose . Following ingestion of galenical preparations or of the anthraquinone glycosides discharge of soft stool occurs after a latency of 6 to 8 h. The anthraquinone glycosides themselves are inactive but are converted by colon bacteria to the active free aglycones. Diphenolmethane derivatives p. 177 were developed

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