Gi system pharmacology


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Gi system pharmacology

  1. 1. Pharmacology
  2. 2. General Guidelines for GI Meds <ul><ul><li>Administration Principles: </li></ul></ul><ul><ul><li>List current medications (including OTC drugs and herbal products) and history of allergies to identify any potential risks to client </li></ul></ul><ul><ul><li>Administer doses on time </li></ul></ul><ul><ul><li>Do not break or allow client to chew sustained release or enteric coated preparations (some meds i.e. antacids are supposed to be chewed) </li></ul></ul><ul><ul><li>Provide verbal and written instructions to client </li></ul></ul>
  3. 3. Client Teaching <ul><li>Understand medication actions, side effects, signs of toxicity, importance of follow-up with prescriber and complying with follow-up lab tests and how to self administer </li></ul><ul><li>Do not take OTC drugs or herbal products without consulting prescriber </li></ul><ul><li>Take exactly as prescribed and do not miss or double doses </li></ul><ul><li>Report adverse effects promptly </li></ul><ul><li>Do not discontinue drug without consulting provider </li></ul><ul><li>Do not drink alcohol while taking prescription medications </li></ul>
  4. 4. Chapter 24 <ul><li>Agents Used To Treat Hyperacidity and Gastroesophageal Reflux Disease </li></ul>
  5. 5. Antacids <ul><li>Alkaline chemical agents used for relief of symptoms associated with hyperactivity and PUD </li></ul><ul><li>Primary goal of antacid therapy is the relief of pain </li></ul><ul><li>Pain-reducing effect believed to be due to: </li></ul><ul><ul><li>Acid neutralizing capacity (the higher the better) </li></ul></ul><ul><ul><li>Inhibition of the protein-digesting ability of pepsin </li></ul></ul><ul><ul><li>Increase in the resistance of the stomach lining to irritation </li></ul></ul><ul><ul><li>Increase in tone of the lower esophageal sphincter </li></ul></ul>
  6. 6. Antacids (cont) <ul><li>Systemically absorbed </li></ul><ul><ul><li>i.e. sodium bicarbonate, evervescent solutions </li></ul></ul><ul><ul><li>Highly soluble in gastric fluids; once dissolved, they are absorbed readily </li></ul></ul><ul><ul><li>Rapid onset and short duration of action—must take frequently </li></ul></ul><ul><ul><li>May cause acid-base (metabolic alkalosis) and electrolyte disturbance </li></ul></ul><ul><ul><li>May cause rebound hyperacidity </li></ul></ul><ul><ul><li>Prolonged use causes stress on kidneys </li></ul></ul>
  7. 7. Antacids (cont) <ul><li>Nonsystemic antacids </li></ul><ul><ul><li>Most useful for long-term therapy </li></ul></ul><ul><ul><li>Stays in GI tract </li></ul></ul><ul><ul><li>Does not alter systemic acid-base balance or electrolytes </li></ul></ul><ul><ul><li>Most cause either constipation or diarrhea (can combine agents to cancel these side effects out) </li></ul></ul>
  8. 8. Antacids (cont) <ul><li>3 basic forms: aluminum, magnesium, and calcium based </li></ul><ul><li>Aluminum hydroxide—prolonged use may cause phosphate depletion </li></ul><ul><ul><li>Maalox, Mylanta </li></ul></ul><ul><ul><li>constipation </li></ul></ul><ul><li>Magnesium—caution if impaired renal function; may accumulate and cause toxicity </li></ul><ul><ul><li>Milk of magnesia </li></ul></ul><ul><ul><li>diarrhea </li></ul></ul><ul><li>Calcium carbonate—may cause kidney stones and increased gastric acid secretion </li></ul><ul><ul><li>Tums </li></ul></ul><ul><ul><li>constipation </li></ul></ul><ul><li>Table 24.1 p. 567-568 </li></ul>
  9. 9. Antacids (cont) <ul><li>Many antacid preparations contain the antiflatulent simethicone, which reduces gas and bloating </li></ul><ul><li>Administration : </li></ul><ul><ul><li>Antacids generally taken about 1 hour after eating, and their neutralizing action lasts for about 3-4 hours (ineffective if taken on an empty stomach) </li></ul></ul>
  10. 10. Antacids (cont) <ul><li>Interactions </li></ul><ul><ul><li>Capable of causing several drug interactions when administered with other drugs </li></ul></ul><ul><ul><ul><li>Adsorption (binding) of other drugs to antacids—reduces ability of the other drug to be absorbed </li></ul></ul></ul><ul><ul><ul><li>Chemical inactivation—produces insoluble complexes </li></ul></ul></ul><ul><ul><ul><li>Increased stomach pH—increases absorption of basic drugs and decreases absorption of acidic drugs </li></ul></ul></ul><ul><ul><ul><li>Increased urinary pH—increases excretion of acidic drugs and decreases excretion of basic drugs </li></ul></ul></ul>
  11. 11. Antacids (cont) <ul><li>***Clients should be advised NOT to take other oral medications within 1-2 hours from the time they are taking antacids </li></ul><ul><li>Do not administer within 1-2 hours of any enteric-coated drug product </li></ul>
  12. 12. Histam INE H2 Receptor Antagonists <ul><li>Cime tidine (Tagamet), famo tidine (Pepcid), niza tidine (Axid), and rani tidine (Zantac) </li></ul><ul><li>Used to treat duodenal ulcers, gastric ulcers, and excessive secretion of hydrochloric gastric acid </li></ul><ul><li>Prevent stress ulcers in critically ill clients </li></ul><ul><li>Inhibit action of histamine at parietal cells in stomach—decreased hydrogen ion production= increased pH in the stomach </li></ul><ul><li>Reduce but do not eliminate acid secretion </li></ul>
  13. 13. H2 antagonists <ul><li>Use caution in clients with impaired renal or hepatic function—dosages usually reduced </li></ul><ul><li>Low incidence of side effects </li></ul><ul><li>Occasionally: diarrhea, muscle pain, rash, drowsiness, dizziness, and/or confusion </li></ul><ul><li>Not recommended for nursing mothers or children <16 y/o </li></ul><ul><li>Client teaching: </li></ul><ul><ul><li>Avoid smoking which causes gastric stimulation </li></ul></ul><ul><ul><li>Avoid antacid use within 1 hour of dose </li></ul></ul><ul><ul><li>Once-a-day dosage should be taken at bedtime; if prescribed more than daily, take before meals </li></ul></ul><ul><ul><li>Avoid gastric irritants such as alcohol, aspirin, and NSAIDS </li></ul></ul>
  14. 14. <ul><li>Cimetidine (Tagamet) </li></ul><ul><ul><li>May cause impotence, gynecomastia, and central nervous system effects (i.e. confusion ) </li></ul></ul><ul><ul><li>May increase pharmacological effects and toxicity of many drugs </li></ul></ul><ul><ul><li>Cigarette smoking may diminish effectiveness </li></ul></ul><ul><ul><li>Use of antacids may reduce the absorption of cimetidine </li></ul></ul><ul><ul><li>Administer with or immediately following a meal </li></ul></ul>
  15. 15. PR oton Pump Inhibitors <ul><li>Esome prazole magnesium (Nexium), lanso prazole (Prevacid), ome prazole (Prilosec), rabe prazole (Aciphex) </li></ul><ul><li>Used to treat hyperacidity, GERD, esophagitis </li></ul><ul><li>Suppress gastric acid secretion by blocking final step in gastric acid production through inhibition of H+, K+ATPase (proton pump) in the gastric parietal class </li></ul><ul><li>Hydrogen ions unable to move out of parietal cell into the stomach </li></ul><ul><li>Block all acid secretion </li></ul>
  16. 16. Proton Pump Inhibitors <ul><li>Used to treat erosive or ulcerative GERD or duodenal ulcers, active benign gastric ulcers, and NSAID associated gastric ulcers </li></ul><ul><li>Generally for Short term therapy (4-8 weeks) </li></ul><ul><li>Used for healing and to reduce relapse rates of heartburn in erosive or ulcerative GERD (maintenance therapy) </li></ul>
  17. 17. Administration Considerations <ul><li>May give with antacids </li></ul><ul><li>If unable to swallow capsules, lansoprazole and esomeprazole capsules may be opened and sprinkled on applesauce before taking </li></ul><ul><li>To give per NG tube, dilute capsule contents in 40ml juice </li></ul><ul><li>Omeprazole(Prilosec), pantoprazole (Protonix), and rabeprazole (Aciphex), must be swallowed whole </li></ul><ul><li>Should be taken 30-60 min before breakfast </li></ul>
  18. 18. Proton Pump Inhibitors <ul><li>Side/adverse effects </li></ul><ul><ul><li>Headache, diarrhea, constipation, abd pain, nausea, flatulence </li></ul></ul><ul><ul><li>Rash, hyperglycemia, dizziness, pruritis, dry mouth </li></ul></ul><ul><ul><li>May increase liver enzymes </li></ul></ul>
  19. 19. Proton Pump Inhibitors (cont) <ul><li>Esomeprazole (Nexium)—highest healing effect on esophagus </li></ul><ul><ul><li>Action decreased by food; should be taken on an empty stomach </li></ul></ul><ul><ul><li>In combination with clarithromycin and amoxicillin has been approved for treatment (and cure) of pts with Helicobacter pylori infection and duodenal ulcer </li></ul></ul><ul><ul><li>SE: diarrhea, abdominal pain, nausea </li></ul></ul><ul><ul><li>20-40mg daily X 4-8 weeks </li></ul></ul>
  20. 20. Proton Pump Inhibitors <ul><li>Lansoprazole (Prevacid) </li></ul><ul><ul><li>In combination with clarithromycin and amoxicillin has been approved for treatment (and cure) of pts with Helicobacter pylori infection and duodenal ulcer </li></ul></ul><ul><ul><li>15-30mg daily X4-8 weeks </li></ul></ul><ul><ul><li>Not recommended for use in children </li></ul></ul>
  21. 21. Proton Pump Inhibitors (cont) <ul><li>Omeprazole (Prilosec) </li></ul><ul><ul><li>GERD and esophagitis </li></ul></ul><ul><ul><li>20-40mg daily X 4-8 weeks </li></ul></ul><ul><ul><li>In combination with clarithromycin and amoxicillin has been approved for treatment (and cure) of pts with Helicobacter pylori infection </li></ul></ul>
  22. 22. Sucralfate (Carafate) <ul><li>Treatment of ulcers and chronic PUD </li></ul><ul><li>Binds to the base of ulcers and erosions, forming a protective barrier over the base of this area </li></ul><ul><li>Limits access of pepsin </li></ul><ul><li>Protects ulcer from further attack by acid, pepsin, and bile salts </li></ul><ul><li>Does little to neutralize gastric acid </li></ul><ul><li>Short term treatment (up to 8 weeks) or at a reduced dose for maintenance therapy </li></ul><ul><li>1 gram 4Xdaily on an empty stomach: 1 hour before each meal and at bedtime </li></ul>
  23. 23. Misoprostol (Cytotec) <ul><li>Synthetic prostaglandin analog </li></ul><ul><li>Decrease gastric acid secretion and exert a protective effect on the mucosal surface of the stomach </li></ul><ul><li>Prevention of gastric ulcers in patients taking NSAIDS (i.e. aspirin) </li></ul><ul><li>SE: diarrhea, abdominal pain, uterine contractions and cause miscarriage—contraindicated for use by pregnant women </li></ul>
  24. 24. Misoprostol <ul><li>Reinforce client teaching: </li></ul><ul><ul><li>Avoid gastric irritants such as caffeine, alcohol, smoking, and spicy foods </li></ul></ul><ul><ul><li>Follow contraceptive practices while on misoprostol </li></ul></ul><ul><ul><li>Report abnormal vaginal bleeding </li></ul></ul><ul><ul><li>Increase fluids and fiber to decrease constipation </li></ul></ul>
  25. 25. Metoclopramide (Reglan) <ul><li>Stimulates motility of upper GI tract without stimulating the production of gastric, biliary, or pancreatic secretions </li></ul><ul><li>Increases force of gastric contractions, relaxes pyloric sphincter, increases LES pressure (decreasing GERD), and increases peristalsis in small intestine </li></ul><ul><li>Accelerates gastric emptying and passage of gastrointestinal contents </li></ul><ul><li>Adverse effects: CNS depression, gastrointestinal upset, parkinsonism-like reactions </li></ul><ul><li>10mg 4X daily, 30 minutes before each meal and at bedtime </li></ul>
  26. 26. Gastrointestinal Enzymes <ul><li>Congenital abnormality, disease, advancing age, or surgery may cause a deficiency in gastrointestinal enzymes that normally assist in food digestion </li></ul><ul><li>Many of these enzymes may be provided orally using commercially available products </li></ul><ul><li>Pancreatic enzymes i.e. pancrelipase, pancreatin </li></ul><ul><li>Enzymes that help digest lactose i.e. lactase </li></ul>
  27. 27. Pancreatic Enzymes <ul><li>Deficiencies: Pancreatitis, pancreatic cancer, cystic fibrosis, GI surgery </li></ul><ul><li>Enzymes: Pancrealipase and Pancreatin </li></ul><ul><li>Required for proper digestion of fats, proteins, and complex carbohydrates </li></ul><ul><li>Most derived from pigs or cows (monitor for sensitivity) </li></ul><ul><li>Usually enteric coated tablets or capsules containing enteric coated enzyme beads </li></ul><ul><li>Should be taken in conjunction with every meal and snack </li></ul>
  28. 28. Lactase Enzyme <ul><li>Lactose intolerance due to inadequate production of lactase enzyme </li></ul><ul><li>S/S lactose intolerance: diarrhea, flatulence, bloating shortly after milk consumption </li></ul><ul><li>LactAid, Lactrase, Dairy Ease </li></ul>
  29. 29. Emetics and Antiemetics
  30. 30. Antiemetics <ul><li>Given to prevent and treat nausea and vomiting due to motion sickness, CNS disorders, administration of certain drugs, radiation therapy </li></ul><ul><li>Vomiting center (VC) in the brain that is responsible for initiating the necessary physiologic events that lead to nausea and eventually vomiting (along with the chemoreceptor trigger zone--CTZ) </li></ul><ul><ul><li>Stimulated by neurotransmitters </li></ul></ul>
  31. 31. Antihistamines and Anticholinergics <ul><li>Anticholinergics </li></ul><ul><ul><li>i.e. scopalamine </li></ul></ul><ul><ul><li>Bind to and block acetylcholine receptors—preventing nauseous stimuli from being transmitted </li></ul></ul><ul><ul><li>Limit stimulation of the emetic center </li></ul></ul><ul><li>Antihistamines </li></ul><ul><ul><li>i.e. meclizine (Antivert), diphenhydramine (Benadryl), promethazine (Phenergan) </li></ul></ul><ul><ul><li>Block histamine H2 receptors, preventing cholinergic stimulation </li></ul></ul>
  32. 32. Antihistamines and Anticholinergics <ul><li>Anticholinergic side effects </li></ul><ul><ul><li>Dry mouth, urinary retention, blurred vision </li></ul></ul><ul><ul><li>Use with caution in clients with benign prostatic hypertrophy and narrow-angle glaucoma </li></ul></ul>
  33. 33. Neuroleptic agents <ul><li>i.e. chlorpromazine (Thorazine), droperidol (Inapsine), perphenazine, and prochlorperazine (compazine) </li></ul><ul><li>Prevent nausea and vomiting by blocking dopamine receptors on the CTZ </li></ul><ul><li>Many of the neuroleptics also have anticholinergic actions </li></ul><ul><li>Adverse effects: orthostatic hypotension, sedation, tardive dyskinesia </li></ul>
  34. 34. Prokinetic Agents <ul><li>i.e. metoclopramide (Reglan), cisapride </li></ul><ul><li>Block dopamine, but also stimulate acetylcholine to increase gastric emptying </li></ul>
  35. 35. Serotonin-Blocking Agents <ul><li>(serotonin antagonists) </li></ul><ul><li>Initially used for treatment of chemotherapy-related n/v </li></ul><ul><li>i.e. ondansetron (Zofran), granisetron(Kytril), dolasetron mesylate (Anzemet), and palonosetron HCl (Aloxi) </li></ul><ul><li>Prevent transmission of triggers that cause nausea and vomiting </li></ul>
  36. 36. Aprepitant (Emend) <ul><li>Used in conjunction with serotonin antagonists and a corticosteroid, such as dexamethasone (Decadron) for the treatment of chemo related delayed n/v </li></ul>
  37. 37. Emetics <ul><li>Substances that induce vomiting—becoming less common </li></ul><ul><li>Treatment of oral drug overdose and poisoning </li></ul><ul><li>Not used with acid or corrosive poisonings </li></ul><ul><li>Assess risk for aspiration </li></ul><ul><li>Ipecac syrup </li></ul><ul><li>Do not use with charcoal </li></ul>
  38. 38. Laxatives and Antidiarrheals
  39. 39. Laxative Classifications <ul><li>Stimulant </li></ul><ul><li>Saline </li></ul><ul><li>Bulk-forming </li></ul><ul><li>Lubricant </li></ul><ul><ul><li>Stool softeners </li></ul></ul><ul><ul><li>Suppositories </li></ul></ul><ul><li>Lactulose </li></ul><ul><li>Enemas </li></ul>
  40. 40. Stimulant Laxatives <ul><li>i.e. bisacodyl (Dulcolax), cascara sagrada, senna (Senokot) </li></ul><ul><li>Increase motility of the GI tract by chemical irritation of the intestinal mucosa or by a more selective action on specific nerves in the intestinal wall </li></ul><ul><li>Increase secretion of water into both the small and large intestines </li></ul><ul><li>Produce a watery, often diarrheal stool </li></ul><ul><li>Many absorbed into systemic circulation (side effects i.e. rash, discoloration of urine) </li></ul><ul><li>May cause dependence </li></ul>
  41. 41. Saline Laxatives <ul><li>Magnesium citrate, magnesim hydroxide (MOM), magnesium sulfate (epsom salts), sod </li></ul><ul><li>Draw water through the intestinal wall by osmotic action and increase fluidity of stool and stimulate greater intestinal motility </li></ul><ul><ul><li>Result in: bowel distention, increased peristalsis, and evacuation </li></ul></ul><ul><li>Unpleasant taste, may be absorbed systemically </li></ul><ul><li>Prolonged use may cause dehydration </li></ul><ul><li>Short term. Used in preps for diagnostic procedures </li></ul>
  42. 42. Saline Laxatives <ul><li>Contain salt </li></ul><ul><li>Unpleasant taste </li></ul><ul><li>Systemically absorbed </li></ul><ul><li>Result in: </li></ul><ul><ul><li>Poor client compliance </li></ul></ul><ul><ul><li>Risk for dehydration </li></ul></ul><ul><ul><li>Risk for congestive heart failure </li></ul></ul>
  43. 43. Bulk Forming Laxatives <ul><li>Citrucel, fibercon, metamucil </li></ul><ul><li>Safest form </li></ul><ul><li>Absorb fluid and swell in the intestine, stimulating peristaltic action </li></ul><ul><li>Slow effect, 12-72 hours to produce response </li></ul><ul><li>Normally formed stools </li></ul><ul><li>Not systemically absorbed </li></ul><ul><li>Should always be taken with a large volume of fluid </li></ul><ul><li>Can cause esophageal obstruction, fecal impaction if chewed or taken in dry powder form </li></ul>
  44. 44. Lubricant Laxatives <ul><li>Liquid petrolatum (Mineral oil) </li></ul><ul><ul><li>Not digestible or absorbable </li></ul></ul><ul><ul><li>No systemic effects </li></ul></ul><ul><ul><li>Administer oral or rectal </li></ul></ul><ul><li>Oils that act as lubricants to facilitate passage of fecal mass through intestine </li></ul>
  45. 45. Stool Softeners <ul><li>i.e. docusate sodium (Colace) </li></ul><ul><li>Detergent like drugs that permit easier penetration and mixing of fats and fluids with the fecal mass </li></ul><ul><li>Softer, more easily passed stool </li></ul><ul><li>Not systemically absorbed </li></ul><ul><li>Do not irritate the intestine or stimulate peristalsis </li></ul>
  46. 46. Suppositories <ul><li>Usually in a wax base </li></ul><ul><li>Administered rectally </li></ul><ul><li>Absorbed systemically </li></ul><ul><li>Available containing stimulant drugs </li></ul><ul><ul><li>Glycerin </li></ul></ul><ul><ul><ul><li>Absorbs water from tissues, creating more mass </li></ul></ul></ul><ul><ul><li>Bisacodyl </li></ul></ul><ul><ul><ul><li>Induces peristaltic contraction by direct stimulation of sensory nerves </li></ul></ul></ul><ul><li>May be overused </li></ul>
  47. 47. Long-Term Use <ul><li>Long-term use of laxatives often results in decreased bowel tone and may lead to dependency. </li></ul><ul><li>Encourage </li></ul><ul><ul><li>A healthy, high-fiber diet </li></ul></ul><ul><ul><li>Increased fluid intake </li></ul></ul>
  48. 48. Lactulose <ul><li>Sugar (two monosaccharides )—not digested or absorbed in the stomach or small intestine and passes to the colon unchanged </li></ul><ul><li>Digested by colon bacteria—forms acidic substances that draw water into the colon </li></ul><ul><li>Also causes ammonia from the blood to pass into the colon </li></ul><ul><li>May mix with fruit juice, water or milk to improve taste </li></ul>
  49. 49. Polyethylene Glycol Electrolyte Solution <ul><li>(CoLyte, GoLYTELY) </li></ul><ul><li>Oral administration rapidly causes large volume of water to be retained in the colon </li></ul><ul><li>Results in induction of diarrheal state within 30-60 minutes; administration continued over 3 hours—complete evacuation and cleansing of bowel w/in 4 hours </li></ul><ul><li>Consume 4 liters of solution within 3 hours at a rate of 240ml every 10 minutes </li></ul><ul><li>Mixture of salts—Little change in water or electrolyte balance </li></ul>
  50. 50. Enemas <ul><li>Administration of liquids directly into lower colon </li></ul><ul><li>Hyperosmotics </li></ul><ul><ul><li>Solutions contain salts (e.g., Fleet enema) </li></ul></ul><ul><li>Solutions containing salts act by osmotically drawing fluid into the colon to initiate the defecation reflex </li></ul><ul><li>Soap, glycerin, and mineral oil also used </li></ul>
  51. 51. AntiDiarrheal Agents <ul><li>Proper diagnosis before symptomatic treatment begun </li></ul><ul><li>Drug therapy </li></ul><ul><ul><li>Reduce motility of the GI tract, permitting normal dehydration of intestinal contents </li></ul></ul><ul><ul><li>Remove irritants from the GI tract </li></ul></ul><ul><ul><li>Replace microorganisms that normally inhabit the intestine, but may have been destroyed by antibiotics </li></ul></ul>
  52. 52. Reduce GI Motility <ul><li>Opium powder, tincture of opium, paregoric </li></ul><ul><li>Opiates that contain morphine reduce propulsive movement of the small intestine and colon and permit dehydration of intestinal contents </li></ul><ul><li>May lead to dependence with prolonged use and CNS depression with even occasional use </li></ul><ul><li>Monitor closely </li></ul><ul><li>Lomotil and Imodium, although not opium derivatives, are chemically related to meperidine, another narcotic </li></ul><ul><li>Anticholinergic drugs also used—reduce intestinal motility </li></ul>
  53. 53. Adsorbents <ul><li>Kaolin, bismuth salts, attapulgite, aluminum hydroxide </li></ul><ul><li>Most commonly used antidiarrheal agents </li></ul><ul><li>Claylike materials administered in a tablet or liquid suspension form after each loose bowel movement </li></ul><ul><li>Can bind drugs, digestive enzymes, toxins, bacteria, and other noxious substances that may be the cause of the diarrheal condition </li></ul><ul><li>Should not be used w/in several hours of other oral drugs </li></ul><ul><li>Little scientific proof that they work </li></ul>
  54. 54. Lactobacillus <ul><li>Lactobacillus acidophilus—normal flora of GI tract </li></ul><ul><li>Treatment of diarrhea associated with antibiotic therapy </li></ul><ul><li>Must be kept refrigerated </li></ul>