GI Pharm

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GI Pharm
2012-02-08 19:46:24
Block Five Lin

GI Pharm
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  1. List the classes of drugs that decrease intragastric acidity
    • Antacids
    • H2 Receptor Antagonists
    • Proton Pump Inhibitors
  2. List the antacids
    • Na bicarbonate
    • Ca carbonate
    • Mg hydroxide
    • AI hydroxide
  3. List the H2 receptor antagonists
    • Cimetidine
    • Ranitidine
    • Famotidine
    • Nizatidine
  4. Proton pump inhibitors
    • Omeprazole
    • Iansoprazole
    • Rabeprazole
    • Pantoprazole
    • Esomeprazole
  5. List the mucosal protective agents
    • Sucralfate
    • Misoprostol
    • Bismuth subsalicylate
  6. Antacids:
    What are they?
    Clinical Uses
    Side effects
    • Weak acids
    • MOA: decreases intragastric acidity by reacting with gastric HCl to form a salt and water
    • Clinical uses: dyspepsia, acid-peptic disorders
    • Side effects: belching and metabolic alkalosis (CO2), diarrhea (Mg) or constipation (Al)
    • Fluid retention (NaCl), hypercalcemia, decreased absorption of other medicines
  7. What is the MOA for H2 Receptor Antagonists?
    • Competitive inhibition at the parietal cell H2 receptor (decreased cAMP)
    • Effective at inhibiting nocturnal acid secretion (stim by histamine) but have a modest impact on meal-stimulated acid secretion (stim by gastrin, Ach and histamine)
  8. List the clinical uses for H2 receptor antagonists
    • GERD (longer duration than antacids)
    • Peptic ulcer disease (replaced by PPI)
    • Prevention of bleeding from stress-related gastritis
  9. H2 receptor Antagonists:
    Side effects
    • Side effects:
    • <3%: diarrhea, HA, fatigue, constipation
    • Cross placenta and is secretedin breast milk
    • Blocks cardiac H2 receptor (rapid IV bradycardia/hypotension)
    • CNS (confusion, hallucination, agitation)
    • Cimetidine: gynecomastia, impotence, galactorrhea
  10. H2 receptor Antagonists:
    Drug interactions
    • Cimetidine and rantidine: inhibit p450 drug metabolism
    • Inhibit gastric first-pass metabolism of alcohol, esp in women (except for famotidine)
  11. Put these drugs in order of relative potency:
    • Cimetidine: 1
    • Ranitidine: 4-10x
    • Nizatidine: 4-10x
    • Famotidine: 20-50x
  12. What are PPIs?
    Omeprazole and esomeprazole specifically
    What is their MOA?
    • Lipophilic weak bases administered as inactive prodrugs.
    • Enteric-coated for delayed release.
    • Omeprazole is a racemic mixutre of R- amd S- isomers
    • Esomeprazole is the S-isomer (active) of omeprazole
  13. What is the MOA for PPIs?
    • MOA: prodrugs are protonated and concentrated in parietal cell canaliculus; converted to the active thiophilic sulfonamide cations which inactivate H+/K+ ATPase irreversibly
    • They should be taken 30 minutes before meals
  14. Describe the pharmacodynamics od PPIs
    They inhibit both fasting and meal-stimulated secretion becasue they inhibit the final common pathway
  15. What are the clinical uses of PPIs?
    • GERD (most effective)
    • Peptic ulcer disease
    • H.pylori 'triple therapy' (w/ clarithromycin & amxoicillin or metronidazole)
    • Prevention of stress-related mucosal bleeding
    • Gastrinoma and other hypersecretory conditions
  16. List the side effects of PPIs
    • Safe (1-5% diarrhea, HA, abdominal pain)
    • Decreased oral vitamin B12 absorption
    • Respiratoy and enteric infections
    • Increased serum gastrin
  17. List the drug interactions of PPIs
    • All PPIs are metabolized by hepatic p450 cytochromes
    • Altered intragastric acidity affects other drug bioavailability
  18. Sucralfate
    • Mucosal protective agent- negatively charged
    • A salt of sucrose and sufated Al hydroxide
    • MOA: Forms a viscous paste that selectively binds to ulcers or erosions
    • Clinical uses: decreases GI bleeding
    • Side effects:
    • no systemicadverse effects
    • Constipation
    • May bind to other meds
  19. Misoprostol (PGE1 analog)
    • Mucosal protective agent
    • MOA: non-competitive inhibition of histamine-mediated cAMP production in parietal cells
    • Clinical uses: NSAID-induced peptic ulcer
    • Side effects: diarrhea, cramping abdominal pain, stimulate uterine contractions
  20. Bismuth subsalicylate (OTC)
    • MOA:
    • - Bismuth: coats ulcers and erosions
    • - Salicylate: inhibits intestinal prostaglandin & CI secretion
    • Clinical uses: dyspepsia, acute diarrhea
    • Side effects: Black stool (bismuth), dark tongue. Salicylate toxicity- nausea, vomiting, sweating, rapid breathing, ringing in ears, fever
  21. List the classes of drugs that stimulate GI motility (prokinetics)
    • Cholinomimetics
    • Dopamine D2 receptor antagonists
    • Macrolides
    • Chlorine channel activator
  22. Bethanechol
    • Cholinomimetic agent
    • Stimulates GI motility
    • Stimulates M3 receptors on muscle cells and myenteric plexus synapses
    • Long duration- resistant to acetylcholinesterase
  23. Neostigmine
    • Cholinomimetic agent
    • Stimulates GI motility
    • Acetylcholinesterase inhibitor
    • Enhances gastric, intestinal and colonic emptying
    • Useful in acute colonic pseudo-obstruction (AKA Ogilvie syndrome)
    • Side effects: cholinergic effects (salivation, nausea, vomiting, diarrhea, bradycardia)

    Given with atropine
  24. Metoclopramide and Domperidone
    • Dopamine D2 receptor antagonists
    • Stimulate GI motility
    • MOA: block the activity of dopamine receptor (activation of dopamine receptors in GI inhibits cholinergic smooth muscle stimulation)
    • Clinical uses: Anti-nausea/anti-emetic (act on D2 receptors in medulla), GERD, impaired gastric emptying, nonuclear dyspepsia,
  25. Metoclopramide and Domperidone: What are the side effects?
    • Dopamine inhibits prolactin
    • Galactorrhea, gynecomastia, impotence (increased prolactin)

    Domperidone does not cross the BBB

    Metoclopramide: CNS syndromes (restlessness, drowsiness, insomnia, anxiety, agitation), extrapyramidal effects (dystonia, parkinsonian)- avoid long term use!
  26. Erythromycin
    • Macrolide
    • Stimulate GI motility
    • Stimulate motilin receptors on GI smooth muscle
    • Used in patients with acute upper GI hemorrhage to promote gastric emptying of blood prior to enoscopy
  27. Lubiprostome (PGE1 derivative)
    • Chloride channel activator
    • Stimulates GI motility
    • Increases secretion of chloride-rich fluid which promotes bowel movement
    • Treats idiopathic chronic constipation
    • Side effects: nausea (30%), diarrhea, headache