GI Drugs

1. GI Drugs By Dr. L. Saarmann

2. Anti-diarrheals • Adsorbents – coat mucosa, bind to toxins and eliminated in feces • Anticholinergics – see neuro drugs • Opiates – decrease motility

3. Laxatives • Bulk-forming – absorb water, distend bowel • Emollient– lower surface tension, lubricate • Saline – incrosmotic pressure • Stimulants – inc. peristalsis • Hyperosmotic – inc fecal water content

4. Antacids • combines with H+ ions to form water so H+ is pulled out of circulation and leads to increased pH of stomach. • Changes in pH decrease pepsin (digestive) activity

5. H2 antagonists • Parietal cells of stomach produce H+ ions. • H2 antagonists bind to H2 receptors on parietal cells so receptors become unresponsive to acetylcholine and gastrin •  decreased H+

6. Proton Pump Inhibitors • Bind irreversibly to H+/K+ATPase. • Cuts off energy to proton pump •  blocks all acid secretion.

7. Anti-diarrheals • Adsorbents– coats mucosa, bind to toxins and eliminated in feces • SE: inc bleeding time; constipation, tinnitus, metallic taste, blue gums, confusion w/ high doses by elderly • bismuth subsalicylate [PeptoBismol] • attapulgite [Keopectate] • Anticholinergics– The prototypical anticholinergic, atropine,decr output of gastric/intestinal secretions; decr GI motility & tone • SE: increasing heart rate, depressing salivary and bronchial secretion, decrease sweating, dilate pupils, inhibit micturition, causes constipation • Opiates– decreases motility • SE: drowsiness, dizziness, N/V/A/C, urinary retention, flushing, rash urticaria • diphenoxylate & atropine [Lomotil] Rx • loperamide [Imodium] OTC • paregoric & tincture of opium

8. Laxatives • Bulk-forming – absorb water, distend bowel • SE: impaction above stricture, fluid overload • Drugs: Fiber based • methylcellulose [Citrucel] • psyllium [Metamucil] • Emollient – decrease surface tension, bring fat & water into stool, lubricate • SE: rash, decr vit. absorption, lipid pneumonia (only if liq form is aspirated) • mineral oil • dusocate [Colace] • Saline – increase osmotic pressure in intestine • magnesium salts [MOM, Fleets Enemas] • Stimulants – increase peristalsis • SE: rash, gastric irritation, malabsorption of nutrients • phenolthalene (off market) • Hyperosmotic – increase fecal water content of large intestines • SE: abd. Bloating • polyethylene [GoLytely] • lactulose [Cephulac]

9. Antacids • Action - Combine c H+ to form water  incrpH of stomach. Changes in pH decrpepsin (digestive) activity. • SE: • Mg preps  diarrhea • Ca++ & Aluminium preps  constipation • Systemic alkalosis with overuse • Ca++ starts and stops  Rebound hyperacidity • Interactions: • Chelate • combines with other drugs and lessens their absorption • Alters pH of stomach • increased absorption of basic drugs • decreased absorption of acidic drugs • Alter urine pH • increased excretion of acidic drugs • decreased excretion of basic drugs • Mg (MOM) • Al & Mg (Maalox, Mylanta,Riopan) • one causes diarrhea one causes constipation so they even out • Ca (Tums)

10. H2 antagonists • Action - Parietal cells of stomach produce H+ ions. H2 antagonists bind to H2 receptors on parietal cells so receptors become unresponsive to acetylcholine and gastrin  decreased H+ • SE: RARE • HA, dizziness, malaise, depression (elderly) • Myalgia, N/D/C, rash • Inc BUN and liver fx • Blood dyscrasias • Loss of libido, impotence • Drugs all are OTC so many misdiagnosed diseases (esoph. CA) • cimetidine [Tagamet] • famotidine [Pepcid] • nizatidine [Axid] • ranitidine [Zantac]

11. Proton Pump Inhibitors • Bind irreversibly to H+/K+ATPase. Cuts off energy to proton pump  blocks all acid (H+) secretion. • Uses: • GERD, PUD, • NSAID induced stomachGI ulcers only • hypersecretory states (zollenger-ellison syndrome) • SE: • HA, dizziness, • N/V/D/A, rash, alopecia, fever, fatigue, back pain • Blood dyscrasias • Drugs • omeprazole [Prilosec] OTC • esomeprazole [Nexium] • lansoprazole [Prevacid] Delayed release capsules can be opened for dysphagia patients

12. Proton Pump Inhibitors • SE: • HA, dizziness, • N/V/D/A, rash, alopecia, fever, fatigue, back pain • Blood dyscrasias • Drugs • omeprazole [Prilosec] OTC • esomeprazole [Nexium] • lansoprazole [Prevacid] Delayed release capsules can be opened for dysphagia patients

13. Proton Pump Inhibitors • Interactions: cause higher plasma levels of these three drugs • Dilantin, coumadin • valium Prevacid has the least interaction problems

14. Other Drugs • sucralfate [Carafate] in an acid environ, Carafate becomes a thick negatively charged paste and binds to positively charges ulcers (fills them in and protects them from H+) • Take before meals • Pastelike • SE: • Constipation & nausea • Interactions: • Impede absorption of dilantin and coumadin

15. Other Drugs • misoprostol [Cytotec] • synthetic Prostaglandin E1 that protects stomach lining • Uses: prevent NSAID ulcers • SE: diarrhea, N/V, spotting, cramps, • miscarriage is possible • used as an abortive agent

16. Drugs for IBD • Aminosalicylatesdecrinflam (decr prostaglandins and leukotrienes) • mesalamine [Asacol] • SE: stomach cramps, diarrhea, N/V, rhinitis • decreases digoxin absorption • sulfasalazine [Azulfidine] • SE: GI, HA, allergy • decreases dilantin absorption • incr effects of oral hypoglycemics • BRMs • infliximab[Remicade] – monoclonal antibody • Given IV • SE: immunosuppression, liver damage, stomach pain

17. Drugs for IBD • Other • for IBS (constipation reliever) • tegeserod[Zelnorm] • 5HT4 inhibitor • SE: HA, N, gas, back pain.

18. Immunsuppressantsfor IBD • Selectively suppress lymphocytes • azathioprine [Imuran] – antagonizes purine  suppression of T cells • cyclosporine [Sandimmune] & • tacrolimus [Prograf] • inhibit release of interleukin-2 • don’t suppress bone marrow • Uses: prevent & tx transplant rejection • SE: infections • Imuran – problems with bone marrow, liver, ulcers • Cyclosporine – kidney, liver, neuro (tremors), HPT, high K+, hirsutism, gingival hyperplasia, nvd