PHRD5985 Pharmacotherapy Lecture 1 - GI Pharm

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PHRD5985 Pharmacotherapy Lecture 1 - GI Pharm
2014-01-27 22:43:51
GI Pharmacotherapy

GI Pharmacotherapy
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  1. where majority of absorption occurs
    villi of small intestine
  2. where first pass metabolism occurs
  3. how absorbed nutrients are transported to the liver
    portal vein
  4. contains majority of microbiome
    large intestine
  5. H2 agonists treat...
    acid reflux
  6. cimetidine, ranitidine, famotidine, nizatidine
    competitive inhibitors of H2 receptors
  7. causes inhibition of CYP450 oxidative metabolism of other drugs
  8. H2 antagonist site of action
    parietal cell
  9. M1 muscarinic antagonist that blocks ACh at the paracrine cell
  10. pirenzepine treats..
    peptic ulcers
  11. pirenzepine's site of action for stomach acid production
    M1 receptor on the ECL cell (prevents histamine release)
  12. -azole's
    proton pump inhibitors
  13. all GI regulatory pathways converge on the...
    proton pump
  14. only cell the proton pump is expressed in
    parietal cell
  15. PPI mechanism of action
    drugs are protonated in acid environment -> stuck in outside stomach where PP's are -> drug binds covalently to pump -> active site blocked on extracellular face
  16. how PPI's reach parietal cells
    via bloodstream to small intestine
  17. decreased acid secretion causes a reflex increase in...
  18. misoprostol
    PGE1 analog (slowly metabolized)
  19. how prostaglandins protect against acid damage (2)
    • 1) inhibit PP
    • 2) induce mucus secretion
  20. used to protect arthritis patients on chronic high dose NSAID therapy
  21. sites of GI prostaglandin action
    • parietal cell
    • epithelial cell
  22. antacid residence time limit
    30 minutes
  23. antacid speed comparison (Al, Mg, Ca)
    Ca > Mg > Al
  24. gastric motility -> Al vs Mg
    Mg increases motility, Al decreases it
  25. complex of sulfated sucrose with Al(OH)3
  26. inhibits pepsin mediated destruction of unprotected stomach tissue surfaces by coating it with a protective layer
  27. 2 types of intestinal muscles
    • 1) longitudinal (outer)
    • 2) circular (inner)
  28. where the enteric NS lies
    between the longitudinal and circular muscles
  29. largest secondary lymphoid organ
  30. parasympathetic regulation by ACh
    stimulate gastric motility
  31. PNS regulation by 5HT and DA
    modulates gastric motility
  32. peptide secreted by M cells during fasting
  33. fasting contractile activity caused by motilin that travels the length of the intestine
    migrating motor complex (MMC)
  34. D2 antagonist that enhances motility of the smooth muscle from esophagus to small intestine
  35. metoclopramide (D2 antagonist) MOA
    enhancement of cholinergic neurons of the PNS
  36. blocked by atropine (which blocks cholinergic neurotransmission)
  37. D2 antagonist with decreased digoxin as a side effect
  38. 5HT4 agonists used for IBS
    • tegaserod
    • prucalopride
  39. 5HT4 agonist side effect
  40. 5HT3 antagonists used for IBS
    • alosetron
    • cilansetron
  41. 5HT3 antagonist side effect
  42. antibiotic that also functions as a motilin receptor agonist at low doses
  43. side effects of erythromycin
    • nausea/vomiting
    • Torsades de Pointes
    • Ab resistance
  44. use for erythromycin
    used in ICU if pt doesn't respond to metoclopramide
  45. Torsades de Pointes
    cardiac toxicity manifested as a lengthened QT interval
  46. molecular basis for Torsades des Pointes
    erythromycin inhibits CYP3A4 -> prodrug astemizole is prevented from CYP3A4 metabolism and binds potassium channels to cause longer depolarization times -> arrhythmias
  47. major side effect of opiate antagonists
    bowel dysfunction (constipation)
  48. -opiate antagonists (2)
    • alvimopan
    • methylnaltrexone

    don't cross BBB to access CNS (allow pain relief while decreasing GI side effects)
  49. peptide agonist of guanylate cyclase 2C
  50. linaclotide MOA
    mimics guanylin and uroguanylin, hormones secreted in intestinal lumen after salty meal to inhibit Na+ absorption, and increase water and Cl- excretion
  51. intestinal chloride channel (CLCN2) activator
  52. lubiprostone MOA
    • PGE1 analog
    • CLCN2 activation -> increased Cl- secretion into lumen -> increased water secretion
  53. therapeutic use for lubiprostone & linaclotide
    IBS associated w/ constipation
  54. emetic center
  55. emetic stimuli (4)
    • 1) cerebellum (inner ear)
    • 2) chemoR trigger zone
    • 3) visceral afferents (GI, vagal response)
    • 4) higher centers (sensations, memories)
  56. drug classes that affect emesis (3)
    • 1) drugs that modify signaling through 5HT, DA, HA, and ACh
    • 2) corticosteroids
    • 3) cannabinoids
  57. antihistamine antiemetic MOA
    blocks chemoreceptor trigger zone (anticholinergic & antidopaminergic)
  58. antiemetic antihistamines (5)
    • 1) diphenhydramine
    • 2) dimenhydrinate
    • 3) chlorpheniramine
    • 4) promethazine
    • 5) meclizine

    (1st gen antihistamines)
  59. 5HT antagonists (2)
    • ondansetron
    • granisetron
  60. therapeutic use of odansetron & granisetron (5HT antagonists)
    prevention of nausea caused by chemotherapy
  61. side effects of 5HT antagonists (4)
    diarrhea, constipation, headache, dizzines
  62. dopamine D2 antagonists (4)
    • 1) metoclopramide
    • 2) trimethobenzamide
    • 3) phenothiazines (antipsychotics)
    • 4) butyrophenones
  63. metoclopramide, trimethobenzamide (D2) antagonist MOA
    also function as 5HT3 antagonists -> antiemetic effects
  64. side effects of D2 antagonists (metoclopramide, trimethobenzamide) (2)
    • anxiety
    • depression
  65. DA antagonist antipsychotic phenothiazines (5)
    • 1) chlorpromazine
    • 2) prochlorperazine
    • 3) promethazine
    • 4) perphenazine
    • 5) triflupromazine
  66. cannabinoid used to treat mild-moderate nausea from chemotherapy
    dronabinol (synthetic 9-THC)
  67. combined with dronabinol to block disorientation side effects
  68. antimuscarinic drugs used to treat motion sickness (2)
    • 1) scopolamine¬†
    • 2) benzatropine
  69. primary site of action of antimuscarinic drugs for motion sickness
    vestibular system
  70. benzodiazepines used for antiemesis therapy (2)
    • 1) lorazepam
    • 2) alprazolam
  71. therapeutic use of benzodiazepines
    enhancement of primary antiemetic therapies for severe chemotherapy induced nausea
  72. corticosteroids used as antiemetics (2)
    • 1) dexamethazone
    • 2) methylprednisolone