DrugsAffectingtheastrointestinalSystem分析课件

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1、Drugs Affecting the Gastrointestinal SystemDrugs Affecting the Gastrointestinal System Antiulcerants Digestives Antiemetics Purgatives Antidiarrheals CholagoguesPeptic Ulcers Common disease，incidence rate: 10%12%. Pathogenesis of ulcers Aggressive Factors Defensive FactorsAcid,pepsinBile saltsDrugs

2、(NSAIDs)H.pyloriMucus,bicarbonate layerBlood flow,cell renewalProstaglandinsPhospholipidFree radical scavengersTherapy Purpose： Therapy is directed at enhancing host defense or eliminating aggressive factors; i.e., H. pylori.Peptic UlcersDrugs Used in Peptic Ulcers Antacids Inhibitors of gastric aci

3、d production H2-receptor antagonists Proton pump inhibitors Muscarinic antagonists Gastrin receptor antagonist Mucosal Protectants Anti-Helicobacter pylori. drugs Drugs Used in Peptic UlcersnAntacids ：aluminum hydroxidemagnesium hydroxidenH2- receptor antagonists ：cimetidineranitidinenMuscarinic ant

4、agonists ：atropine Proton pump inhibitors ：omeprazole Gastrin receptor antagonist ：proglumide Mucosal Protectants ：misoprostol Anti-Helicobacter pylori. Drugs ：antibioticsDrugs Used in Peptic Ulcers AntacidsGeneral characteristicsAntacids are weak bases that are taken orally and that partially neutr

5、alize gastric acid and reduce pepsin activity.Antacids reduce the pain associated with ulcers and may promote healing. High doses are required for healing: 40 mEq of base seven times daily. Magnesium hydroxide Magnesium trisilicate Aluminum hydroxide Calcium carbonate Sodium bicarbonate AntacidsH2-r

6、eceptor antagonists Mechanism of action Competitively block the histamine (H2) receptor of acid-producing parietal cells rendering cells less responsive to not only histamine but also to the stimulation of acetylcholine and gastrin. Also up to 90% inhibition of vagal stimulated and gastrin stimulate

7、d acid secretion. complete inhibition has not been shownH2-receptor antagonistsFour FDA-approved:Cimetidine （Tagamet）Ranitidine （Zantac）Famotidine （Pepcid）Nizatidine （Axid）RoxatidineTherapeutic effects: Promote the healing of gastric and duodenal ulcers Gastroesophageal reflux dz GERD Upper GI bleed

8、 GIB May be effective in stress ulcers & peptic esophagitis H2-receptor antagonists Side effect: Overall low 3% CNS: 1% total headache, lethargy ，confusion, depression，hallucinations ENDO： Impotence ，increased prolactin ，gynecomastia HEME: ThrombocytopeniaH2-receptor antagonists Muscarinic antagonis

9、tsAtropine： Block the M1 class receptors reduce acid production abolish gastrointestinal spasm relatively unpopular as a first choice because of high incidence of anticholinergic side effects (dry mouth and blurred vision) H+,K+-ATPase (Proton Pump) inhibitor Irreversible inhibition Must synthesize

10、new enzyme Long duration Omeprazole (Prilosec) Lansoprazole (Prevacid) Pantoprazole RabeprazoleProton pump inhibitorsMechanism of Action Omeprazole（losec） Irreversibly binds to H+/K+ ATPase Prevents H+ ion production & secrection Block all acid secretion = achlorhydria to return to normal must synth

11、esize new H+/K+ ATPase Inhibit H. pyloriOmeprazole（losec）Therapeutic uses Gastroesophageal reflux dz GERD Peptic ulcer Infection with H. pylori plus(Hp) Upper GI bleed GIBLansoprazoleGastrin receptor antagonistProglumide Mucosal Protective Agents A congener of prostaglandin E1 PGs: inhibit gastric a

12、cid secretion exhibit cytoprotective activity enhance local production of mucus or bicarbonate promote local cell regeneration help to maintain mucosal blood flow Misoprostol is approved for use in patients taking NASIDs who are at risk for gastric ulcers Misoprostol produces diarrhea and stimulatio

13、n of uterine contraction. Sucralfate cytoprotective agent stress ulcerations & PUD inhibit H. pylori Bismuth （Pepto-Bismol） inhibit pepsin activity inhibit H. pyloriAgents Used in infection of Helicobacter Pylori Helicobacter pylori，HP Aimed at eliminating H. pyloriBismuth ( Pepto-Bismol)GentamicinA

14、motriptyline (Amoxil )ClarithromycinTetracycline (Achromycin V )Metronidazole (Flagyl )Agents Used in infection of Helicobacter Pylori1990199019701970 Before Before 1970197019801980AntacidsH2-receptor antagonistsProton pump inhibitorsProton pump inhibitors Agents Used in infection of Helicobacter Py

15、lori DigestivesPepsinPancreatinLactasin Antiemetic Drugs Vomiting reflex a coordinated reflex controlled by a bilateral vomiting center in the dorsal portion of the lateral reticular formation in the medulla Pharmacologic intervention relies on inhibition of inputs or depression of the vomiting cent

16、er.Histamine1-receptor antagonist Cholinergic antagonist Dopamine antagonists : Metoclopramide Domperidone （motilium） Therapeutic uses Side effects5-HT3 antagonists Cannabinoids Antiemetic DrugsD2-receptor antagonist (periphery)A weaker antiemetic, fewer extrapyramidal effects.Accelerates gastric emptying; has little effect on the colon