chapter31 drugs used in gastrointestinal diseases.pptVIP

Chapter 31  Drugs Used In Gastrointestinal Diseases §1 Drugs used in peptic ulcer [Pathogenesis of peptic ulcer] 1. Excessive secretion of gastric acid 2. Mucosal protective effect decreasing 3. Infection of Helicobacter Pylori ( HP) Ⅰ. Antacids weak bases : Mg(OH)2 , MgSiO3 , Al(OH)3 CaCO3 Ca(HCO3)2 NaHCO3 actions: 1) neutralize gastric acid→reduce gastric acidity→reduce peptic activity 2) injury from H+ Ⅱ. Gastric antisecretory drugs 1. H2-R antagonists 1.1 mechanism: block H2-R→ reduce the secretion of gastric acid→↓the volume of gastric acid acidity 1.2 clinical uses: ①peptic ulcer ②zollinger-ellison syndrome ③gastroesophageal reflux(胃食管反流) 1.3 adverse reaction: 1) Antiandrogenic effect : gynecomastia, impotency, galactorrhea溢乳 2) Inhibit cytochrome P450 catalyzed oxidative drug metabolism pathway→ reduce clearance of other drugs Cimetidine(西咪替丁;甲氰咪胍): 400 mg bid 4W→80% healing Ranitidine(雷尼替丁) 1) Antisecretive effect is 10 times that of Cimetidine . 2)Less effect on hepatic microsomal metabolism system. 3)Longer duration and less antiandrogenic effect Famotidine(法莫替丁), Nizatidine(尼扎替丁): 1) Antisecretive effect is 30 times that of Cimetidine . 2) Have no effect on hepatic microsomal metabolism system. Ebrotidine(乙溴替丁): 1) ↑Expression of EGF and PDGF→stimulate proliferation of epithelium 2) increase mucus secretion M1- R antagonist:  Pirenzepin(哌仑西平) Proton pump inhibitors Omeprazole(奥美拉唑), lansoprazole(兰索拉唑), rabeprazole, pantoprazole. Mechanism of action Require activation in the acid environment of the secretory canaliculus of the parietal cell Inhibit H+-K+ ATPase irreversibly and inhibit over 95% of gastric acid secretion Clinical uses: superior to H2-R antagonists. Adverse reactions: 1) inhibits gastric secretion→overgrowth of bacteria. 2) hypergastrinemia(高胃泌素血症).