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34 Cards in this Set
- Front
- Back
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What are some important stomach lumen pumps/channels?
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Parietal Cells
H/K ATPase - antiport, move H+ into lumen K/Cl channel - symport, moves both items into lumen |
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Gastric Secretions
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M3 - ACh - Parietal cells - increases Ca++ and activates Histamine
CCK - gastrin - stimulates histamine H2 - histamine - ECL cells in fundus - Parietal cells - secrete H+ EP3 - prostaglandins inhibit acid secretion (NSAIS cause damage here) |
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Gastric defense
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esophageal defense is LES
stomach defenses require good blood flow - secretion of mucus - stimulated by PGE2 and PGI2 - also inhibit acid secretion - secretion of Bicarb - forms buffer between mucus and epithelial cells |
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Peptic Ulcer Disease
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increase in acid, pepsin, NSAIDS, H. Pylori
- or - decrease in mucus or bicarb |
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Antacids
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systemic antacids:
baking soda or alka-seltzer non-systemic antacids: tums, MofM, mylanta, ext weak bases and react with stomach acid simethicone is added to prevent foaming back into esophagus |
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Adverse effects of antacids
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metabolic acidosis
AlOH - causes constipation MgOH - causes diarrhea Al and Mg can cause hypohohatemia - decrease renal function - toxicity be aware of sodium products with CHF |
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Antacid Drug interactions
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gastric or urinary pH may lead to malabsorption of certain drugs
Al and Mg alter gastric motility which can alter absorption decreases bioavailability of iron, theophylline, FQ's, INH, |
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Acid Secretion Inhibitors
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2 groups
H2 Agonists - cimetidine ranitidine, famotidine - decrease gastric juice and H+ content - decrease pepsin secretions Proton Pump Inhibitors - omeprazole, lansoprazole, esomeprazole - irreversible inhibit H/K ATPase - decrease basal and stimulated acid secretion |
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Cimetidine
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initial drug in class - less potent and shorter acting
biotransformed in lever H2RA |
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H2RA Adverse Effects
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headache
itching rashes lethargy and confusion |
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H2RA Drug Interactions
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cimetidine inhbits CYP450 - may increase toxicity of other drugs
other effects similar to antacids |
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H2RA Theraputic Uses
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gastric and duodenal ulcers
GERD Zollinger Ellison syndrome Acute stress Ulcers |
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PPI Theraputic Uses
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Peptic Ulcers
Refractory GERD - omeprazole Zollinger Ellison syndrome Lansoprazole - prevent recurrance of NSAID ulcers |
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PPI adverse effects
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well tolerated
nausea diarrhea flatulence headache dizziness possible gastric cancer |
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PPI drugs Interactions
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Omeprazole - inhibits CYP450
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Agents that enhance Mucosal Defense
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Misoprostol
Sucralfate Bismuth |
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Misoprostol
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PGE1 analog
decreases acid and increases mucus and bicarb used for PREVENTION of peptic ulcers in patients taking NSAIDS less effective against other types of peptic ulcers Adverse effects - cramping diarrhea, nausea, AVOID IN IBD patients It can promote uterine contractions - contraindicated in pregnancy |
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Sucralfate
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presence of acid induced damage. pepsin mediated hydrolysis of mucosal proteins
sucrate forms polymers that adheres to cells and forms barrier - protects ulcer crater may cause constipation |
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Bismuth Compounds
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pepto-bismol
GI ulcers nad heartburn coats ulcer craters - increases mucus and bicarb - inhibits pepsin - antibacterial to H.pylori H2RA is better at healing ulcers can cause dark mouth and stool |
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H. Pylori
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gram negative rod
present in 70-90% of peptic ulcers single agent therapy not effective in erradicating organism |
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eradication of H. Pylori
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metrondiazole + bismuth + tetracycline or amoicillin
PPI + amoxicillin or clarithromycin Ranitidine + bismth + clarithromycon or amoxicillin |
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GERD
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antacids
H2RA and PPI's - inhibit acid secretion and are preferred if problems persist with OTC atacids |
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Metoclopramide
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cholinergic agonist and dopamine antagonist
increases gastric motility - increases esophageal clearance - increases LES pressure and gastic emptying - net effect is to decrease reflux not effective in errosive esophagitis lead to adverse effects of hyperprolactinemia and tardive dyskenisia |
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Laxatives
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enhancing retention of intrluminal water retention by hydrophillic or osmotic mechanisms
decreasing absorption inhibit segment contraction and increase propulsive contractions |
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Dietary Fibers
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bulk forming agents
well tolerated but may cause obstruction or impaction |
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Saline and Osmotic laxation
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saline lax.:
- magnesium salts and phosphate salts - act osmotically to retain water Osmotics - lactulose and mannitol - retain water in colon |
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Stimulant Laxatives
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bisacodyl and phenophthalein
stimulate water and electrolyte secretion |
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Surfactant Laxatives
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docusates and castor oil
wetting and emulsifying agents castor oil - cleaved to ricinoleic acid in the SI and produce a purging effect ricinoleic acid is an anionic surfactant - decrease absorption of fluid and electrolytes and stimulate peristalsis mineral oil - lubricates stool, can decrease fat soluble vitamins -aspiration causes pneumonitis |
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Uses and Abuses
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used to maintain soft feces
contraindicated in patients with cramps, colic, nausea, vomiting, undiagnosed pain |
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Diarrhea
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characterized by watery stools
can be caused by microoranisms, drugs, or toxins can lead to dehydration and electrolyte imbalance |
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Agents causing diarrhea
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adrenergic neuron blocking agents
antimicrobials bile acids tumor products cholinergic agonists and cholinesterase inhibitors laxatives metoclipramide prostaglandins |
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Treatment of Diarrhea
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aim to prevent dehydration and electrolyte imbalances
Opiods (diphenoxylate and atropine and loperamiede) -decrease motility - increase transit time - increase absorption - decrease in secretion |
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Bismuth Subsalicylate
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mild to moderate diarrhea
severe diarrhea - use loperamide |
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Octreotide
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somatostatin - produced by antral D cells
inhibits all GI functions use in HIV diarrhea |
