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Drugs acting on GI tract

Drugs acting on GI tract. Overview of vomiting. Vomiting is a reflex that help get rid of harmful substances from Upper GI Tract It is Stimulates by Chemoreceptor trigger zone (CTZ) Vestibular system Peripheral afferents from the pharynx and GI tract Psychic input from CNS. Antiemetics.

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Drugs acting on GI tract

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  1. Drugs acting on GI tract

  2. Overview of vomiting • Vomiting is a reflex that help get rid of harmful substances from Upper GI Tract • It is Stimulates by • Chemoreceptor trigger zone (CTZ) • Vestibular system • Peripheral afferents from the pharynx and GI tract • Psychic input from CNS www.4medstudents.com

  3. Antiemetics • Cholinergic antagonists:(hyosine) • H1 blockers: ( cyclizine, promethazine) • Dopamine antagonists • Metoclopramide ( inhibits the CTZ) • Phenothiazine (ChropromoZINE, ProchlorperaZINE) • Butyrophenone (HaloperiDOL, CloperiDOL) • Serotonin antagonists (OndanSETRON, GranSETRON) • Cannabinoids (dronabinol, nabilone) • Glucocorticoids (dexomethasone) • Benzodiazepine ( Diazepam, Lorazepam) www.4medstudents.com

  4. Emetics • Drugs used to induce emesis. This is indicated in poisoning • Ipecac( Stimulate the CTZ) • Apamorphine( Dopamine agonist that stimulate the CTZ) www.4medstudents.com

  5. Treatment of Upper GI disorders • The main aims of treatment are • Neutralizing the acidity • Inhibiting acid secretion • Protection of the gastric mucosa www.4medstudents.com

  6. 1. Drugs used to neutralize acidity • Antacids: which are weak bases that bind with acid and produce water and salt • Examples • Sodium Bicarbonate • Aluminum Hydroxide • Magnesium Hydroxide www.4medstudents.com

  7. 2. Inhibition of acid production • H2-Receptor blocker • Cimetidine, Famotidine, Ranitidine • Anticholinergics • Isopropamide & scopolamine • M1- Receptor blocker • Pirezapine • Proton Pump Inhibitors • Omeprazol, Lansoprazole www.4medstudents.com

  8. 3. Protective agents • Sucralfat ( increase mucus production and prevent further damaged mucosa) • Mesoprestol ( which is a Prostaglandin E that is important is cytoprotection in maintaining the integrity between the epithelium cells and inducing bicarbonate production) www.4medstudents.com

  9. Treatment of H.Pylori induced Peptic ulcers • The aim of treatment is irradiation of H.Pylori. Because that causes rapid healing of the damaged mucosa. • 1st line therapy: Clarithromycin, Amoxicillin & Omeprazole • 2nd line therapy: Bismuth subsalicylate, metronidazole, tetracyclin, Omeprazole www.4medstudents.com

  10. Treatment of NSAID Induced peptic ulcer • Neutralizing the acidity (Antacids) • Inhibiting acid secretion (PPI, H2- Blockers) • Protection of the gastric mucosa (sucralfat) • Safer NSAIDS (-COXIB, such as Celecoxib & refecoxib) www.4medstudents.com

  11. Non specific anti-diarrheals • Opiates and opiod containingpreparations( they bind to μ receptors and decrease the transit time and increase absorption). Example: opium tincture and codiene, Diphenoxylate. • Anticholinergics: example; atropin, scopolamine and propamtheline • Adsorbents: Kaolin and pectin • Oral rehydration therapy: which contain suffecient amount of electrolytes and glucose www.4medstudents.com

  12. Anti-diarrheals for specific causes • Traveler’s Diarrhea: • Loporamide • Bismuth subsalicylate ( Bind to toxins produced by E.Coli and V. Cholera) • Inflammatory bowel disease • Sulphasalazine and olsalazine www.4medstudents.com

  13. Drugs used to dissolve Gallstones • The criteria of using this method are: • Small stones (5-10mm) • Cholesterol stones • In cases where surgery is not possible • Asymptomatic cases www.4medstudents.com

  14. Drugs used to dissolve Gallstones • Chenodiol (Chenodeoxycholic acid):inhibits HMG-COA reductase and therefore inhibits cholesterol synthesis & induce bile acid synthesis. • Ursodiol (Ursodeoxycholic acid): inhibits cholesterol secretion in bile but little affect on bile acids. • Methyl-ter-butyl-ether (MTBE): Directly dissolves cholesterol stones www.4medstudents.com

  15. Laxatives • Bulk forming agentsare hydrophelic agents that are poorly absorbed and increase luminal mass therefore induce peristalsis: ex.Methyl-cellulose. • Osmotic agents • Salt osmotic agents (Magnesium sulfate) • Salt-free osmotic agents (lactulose) • Irritantsare agents that irritates the mucosa and induced secretion (ex. castor oil and senna) • Stool softeners (ex. Sodium docusate) www.4medstudents.com

  16. Treatment of amebiasis Ingested cysts Trophozoites • Systemic amebiasis • Metroniadizole • Luminal amebiasis • Didoxanide www.4medstudents.com

  17. Anthelmintics • Mebendazole/ Albendazole* (Inhibits glucose uptake by parasitedecrease ATP production  immobilization • Thiabendazole* (Inhibits microtubules assembly and parasitic metabolism) • Ivermectin* (paralysis of the parasitic muscles by opening Cl- gated channels) • Prazequantel **( paralysis of the warm and activate the immune system) * Are used for nematodes ** Are used fro cestodes www.4medstudents.com

  18. Chemotherapy for GI tumors • Colorectal cancer: • 5-Flurouracil (5-FU): which inhibits DNA synthesis by inhibiting thyamidine synthesis & levamisole: anthelmintic that activate cell mediated immunity • OR 5-FU & Leucovarin (inhibits folate co-enzymes which are required for thyamidine synthesis) www.4medstudents.com

  19. Chemotherapy for GI tumors • Pancreatic cancer • 5-FU &/or Gemcitabine • Gastric cancer • 5-FU & Methyl-CCNU • 5-FU & mitomycin C ( which inhibits DNS synthesis by alkalating double stranded DNA and forming cross links. www.4medstudents.com

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