中医中药药理学外文版 (40).pdf

Chapter 22 Drugs for Digestive Disorders【Learning points】1.Drugs against peptic ulcer 1.1 Antacids Magnesium hydroxide,magnesium trisilicate,aluminum hydroxide,calcium carbonate,and sodium bicarbonate neutralize the gastric acidity in stomach and relieve the erosion of gastric and duodenal mucosa.However,they cant inhibit the secretion of gastric acid.1.2 Gastric acid secretion inhibitors Anti-cholinergic drugs,atropine and selective M1 antagonists,can reduce gastric acid secretion and relieve gastrointestinal spasm.Their adverse effects are mild.H2 receptor blockers such as cimetidine,ranitidine,famotidine,etc.,are available for peptic ulcer.They reduces the nocturnal gastric acid secretion.Among them,cemitidine shows CNS adverse effects.Omeprazole,lansoprazole,pandorazole and rabeprazole,H+-K+-ATPase inhibitors,reduce gastric acid secretion.They benefits reflux esophagitis,peptic ulcer,upper gastrointestinal bleeding,and helicobacter pylori infection.The adverse reactions were peripheral neuritis,serum transaminase increase and bilirubin.Gastrin receptor blockers,such as glutamine,reduces gastric acid secretion via blockade of gastrin receptors and promotes gastric emptying via blockade of cholecystokinin receptors.1.3 Mucosal protectants Prostaglandin E and its derivatives:misoprostol and enprostil can inhibit gastric acid secretion and also reduce pepsin secretion,while they increase the mucus and bicarbonate secrection.It has special effects on peptic ulcer and gastric bleeding caused by non-steroidal anti-inflammatory drugs such as aspirin.Sucralfate promotes gastric mucus and bicarbonate secretion.It promote ulcer healing.Sucralfate inhibits helicobacter pylori.It is used in peptic ulcer,chronic erosive gastritis,reflux esophagitis.Bismuth citrate transforms to bismuth oxide colloid in gastric acid and covers on peptic ulcer,promoting mucus and bicarbonate secretion and inhibiting helicobacter pylori.1.4 Anti-helicobacter pylori Drugs Antibacterials are commonly used in peptic ulcer to kill helicobacter pylori,such as amoxicillin,tetracycline,gentamicin,metronidazole.They often are used in combination with antacids,secretion inhibitors and muscosa protectives.2.Degestive function regulator 2.1 Antiemetic drugs Diphenhydramine and dimenhydrinate,H1 receptor blockers,prevent motion sickness and internal ear vertigo.Scopolamine is also often used in motion sickness.Metoclopramide blocks CTZ dopamine D2 receptors and exerts antiemetic effects via the increase of gastrointestinal motility.However,metoclopramide at large dose intravenous injection or long-term application can cause extrapyramidal response.Domperidone avoids the extrapyramidal response.Cisapride promotes movement of the esophagus,stomach,small intestine up to the colon.Ondansetron selectively blocks central and vagal afferent fiber 5-HT3 receptors,producing a powerful antiemetic effect.It is commonly used in nausea and vomiting caused by chemotherapy and radiotherapy.3.Antidiarrheal and Adsorption Drugs Diarrhea could be controlled via decrease of the gastrointestinal movement.For example,Opioid tincture,compound camphor tincture for severe non-bacterial infectious diarrhea.Diphenoxylate:a pethidine derivative for acute functional diarrhea.Ropividine:a haloperidol derivative with fast,strong and lasting antidiarrhea effect for acute and chronic diarrhea.Astringents release tannic acid in the intestine and bind to the protein on the surface of the intestinal mucosa to form precipitation,reduce inflammatory exudates.They are used in various diarrhea.4.Laxatives Laxatives,including irritating-,permeable-and emollient laxatives,could be used to treat the laxatives.Phenolphthalein,rhubarband bisacodyl stimulate the colonic peristalsis and block electrolyte absorption from GIT,respectively.They are used for constipation and preoperotive preparation for GIT surgery.Magnesium sulfate and sodium sulfate,permeable laxatives,increase the osmostic pressure and prevent absorption of water and promote intestinal peristalsis.They are also used for preoperotive preparation for GIT surgery and constipation.Lactulose and food cellulose are also used to treat constipation.