Gastrointestinal drugs

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Gastrointestinal drugs

  1. 1. Pharmacology Drugs that Affect the Gastrointestinal System
  2. 2. Topics• Peptic Ulcer Disease• Constipation• Diarrhea• Emesis• Digestion
  3. 3. Peptic Ulcer Disease Factors that Factors that Protect AgainstIncrease Acidity Acidity
  4. 4. Peptic Ulcer Disease• Factors Increasing • Factors Decreasing – H. pylori – Mucus production – NSAIDs – Buffers – Acidic agents – Blood flow – Pepsin – Prostaglandins – Smoking
  5. 5. Regulation of Gastric AcidSecretion
  6. 6. H2 Receptor Antagonists• Inhibits gastric acid secretion• No effect on H1 receptors• cimetidine (Tagamet®)• ranitidine (Zantac®)• famotidine (Pepcid®)• nizatidine (Axid®)
  7. 7. H2 Receptor Antagonists• Indications: – PUD – GERD – Prevention of aspiration pneumonia
  8. 8. Proton Pump Inhibitors• K+H+ATPase (Proton Pump)• Irreversible inhibition – Must synthesize new enzyme – Long duration• omeprazole (Prilosec®)• lansoprazole (Prevacid®)
  9. 9. Anticholinergics• pirenzepine (Gastrozepine®)• Other anticholinergics have too many side effects and are not used
  10. 10. Prostaglandin Analog• misoprostol (Cytotec®) – Approved for treating PUD due to long term NSAID use
  11. 11. Antacids• Increase pH of gastric environment• Hydroxides – Aluminum – Magnesium• Carbonates – Calcium
  12. 12. Antacids• Most OTC drugs are combinations – DiGel® – Amphojel® – Maalox® – Milk of Magnesia® – Mylanta®
  13. 13. Antibiotics• Aimed at eliminating H. pylori• bismuth (Pepto-Bismol®)• metronidazole (Flagyl®)• amoxicillin (Amoxil®)• tetracycline (Achromycin V®)
  14. 14. Stool FormationWater absorbed in colon (~90%) – Excessive absorption • Constipation: hard, dehydrated stool • Increases strain on defecation • Harmful for subset of patients – Recent episiotomy, colostomy, hemorrhoids, cardiovascular disease – Inadequate absorption • Diarrhea: soft, non-formed, liquid stool
  15. 15. TermsLaxative Production of soft, formed stool over 1 or more daysCathartic Rapid, intense fluid evacuation of bowel.
  16. 16. Laxatives• Bulk forming• Surfactants• Stimulants• Osmotics
  17. 17. Bulk Forming Laxatives• Absorb water • methylcellulose• Soften and enlarge (Citrucel®) stool • psyllium (Metamucil®)• Fecal swelling • Polycarbophil promotes peristalsis
  18. 18. Surfanctant Laxatives• Lowers surface • Docusate salts tension – Colace® – Facilitates water – Modane Soft®) penetration
  19. 19. Stimulant Laxatives• Stimulate peristalsis • Phenylolpthalein• Increases water and – (Ex-Lax®, Feen-a- electrolytes secretion Mint®, Correctol®) into intestinal lumen • bisacodyl (Ducolax®)• Decreases water and electrolyte reabsorption
  20. 20. Osmotic Laxatives• Poorly absorbed salts • Magnesium hydroxid remain in fecal matter (Milk of Magnesia®)• Pull water into lumen
  21. 21. Antidiarrheal• Diarrhea is usually a compensatory action… – Treatment aimed at cause, no symptom• Opioid receptors in GI tract decrease motility – Increase time for water reabsorbtion
  22. 22. Antidiarrheal Agents• paregoric/opium tincture• diphenoxylate (Lomotil®)• defenoxin (Motofen®)• loperamide (Imodium®)
  23. 23. Vomiting Stimulus
  24. 24. Antiemetics• Serotonin (5HT) Antagonists• Dopamine (DA) Antagonists• Anticholinergics (muscarinic blockers)• Cannabinoids
  25. 25. Serotonin Antagonists• Used to treat side effects of chemotherapy- induced emesis• condansetron (Zofran®)• Doesn’t affect dopamine receptors ∴no extrapyramidal effects• Granisetron (Kytril®)
  26. 26. Dopamine Antagonists• Phenothiazines – prochloraperazine (Compazine®) – promethazine (Phenergan®)• Butyrophenones – haloperidol (Haldol®) – droperidol (Inapsine®)• metoclopramide (Reglan®)
  27. 27. Cannabinoids• Tetrahydrocannabinol (THC) – Active ingredient in marijuana – Dronabinol (Marinol®) – Nabilone (Cesamet®)
  28. 28. Digestion Aids• Useful for inactive vagal stimulus/bypassed duodenum• Pancreatin (Entozyme®)• Pancrelipase (Viokase®)

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