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Flashcards in lower GI pharmacology Deck (48):
1

anti-emetics for cancer chemo

Class I: PRN- lorazepam, prochlorperazine + diphenhydramine, metoclopramide + diphenhydramine. class II: dexamethasone. Class III: ondansetron + Dex. Class IV: Granisetron + Dex. Class V: granisetron + Dex

2

anti-emetics for pregnancy

First line: pyridoxine (B6) + doxylamine (H1 antagonist). If persists: add diphenhydramine or meclizine. Then: proclorperazine (D2 antagonist) or metoclopramide. If dehydration requiring hospitalization: ondansetron. If refractory n/v (2nd trimester): methylprednisone

3

list 5HT3 receptor antagonists

Ondansetron

4

5HT3 antagonists uses

prevent chemotherapy induced n/v, post-op emesis, N/V associated with post-op opioids

5

list Dopamine (D2) receptor antagonists

Prochloroperazine , Metoclopramide (also blocks 5HT3)

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dopamine antagonist side effects

Extrapyramidal symptoms (movement disorders)

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dopamine antagonist uses

Metoclopramide used for n/v of chemotherapy. Prochlorperazine less effective against emetic stimuli in gut (mediated via 5HT3 receptors). But also blocking M and H1 receptors increases their utility in nausea with motion sickness

8

List Antihistamines (1st generation)

Meclizine, promethazine, Diphenhydramine (dimenhydrinate)

9

antihistamine uses

motion sickness and postoperative emesis

10

list Anticholinergic agents

Scopolamine

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Anticholinergic agents uses

Primarily prevention/treatment of motion sickness. Also post operative n/v

12

Anticholinergic agents pharmacokinetics

transdermal- duration of action 72 hrs

13

Which drugs can induce constipation

antimuscarinics, drugs with antimuscarinic side effects (antihistamines, TCAs, antipsychotics), antacids, Ca channel blockers (verapimil), opioids, 5HT3 antagonists

14

List Bulk-forming / fiber laxatives

Psyllium Seed (metamucil)

15

Fiber uses and MOA

first line agent for constipation. Approximates physiological mechanism (facilitates passage-stimulates peristalsis via H20 absorption > bulk expansion)

16

Fiber pharmacokinetics

•Effective in 12-24 hrs to 3 days - take with fluids. May combine and interact with other drugs (digoxin / salicylates), so space dosing

17

List Saline (osmotically-active) cathartics

Mg(OH)2, Polyethylene glycols, lactulose

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Saline (osmotically-active) cathartics uses

Added to fiber as second line/step for constipation.Mg(OH)2 used for mild/moderate constipation. Polyethylene glycol used for bowel cleansing before medical procedures (high volume) or difficult constipation (low volume). lactulose: used in elderly Also used in purging doses for food/drug poisoning

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Saline (osmotically-active) cathartics MOA

Non-absorbable ions > osmotic retention of intestinal water > increased peristalsis

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Saline (osmotically-active) cathartics pharmacokinetics

Mg(OH2): avoid in renal dysfunction. Can lead to electrolyte imbalance. PEG: high volume has electrolyts added to prevent net transfer but low volume solns may lead to electrolyte depletion.

21

List Stimulant / irritant laxatives

Bisacodyl (dulcolax)

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Stimulant / irritant laxatives uses

used for constipation if fiber/saline fails.

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Bisacodyl MOA

increases peristaltic activity via local irritation > accumulation of water and electrolytes > increased motility

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Bisacodyl side effects

electrolyte / fluid deficiencies, severe cramping

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List Wetting agents / emollient laxatives

Docusate (ex lax extra gentle)

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Ducosate MOA

surfactant that acts as stool-softener (facilitates admixture of aqueous and fatty substances)

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Ducosate uses

primary prevention in pts with CV dz, hernia, post partum

28

List meds used for opioid induced constipation

Managed with stool softeners (docusate), stimulant laxatives (bisacodyl - senna), osmotic laxatives (PEG [Miralax®] - milk of magnesia)

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two causes of diarrhea

decreased absorption of fluid/electrolytes (osmotic) or increased secretion of fluid and electrolyes

30

Causes of osmotic diarrhea

Carbohydrate malabsorption (lactose, sorbitol, fructose) , osmotic laxatives (magnesium, colonoscopy preps)

31

causes of secretory diarrhea

bacteria (cholera, e.coli), neuroendocrine tumors, ileal bile salt malabsorption, stimulant laxatives, disordered motility (diabetic neuropathy, IBS)

32

drugs that can induce diarrhea

antibiotics, colchicine (anti inflammatory for gout), digoxin, misoprostol (prostaglandin anolog), muscarinic agents, reserpine, SSRIs

33

Which antibiotics are given for C. difficile, cholera and e.coli?

c. diff: metronidazole, vancomycin, rifaximin. Cholera: doxycycline, tetracycline or macrolide. E. coli: none

34

List antidiarrheal Opioids

Loperamide

35

opioids MOA

•Opioid receptor agonist affecting intestinal motility (m), intestinal secretion (d), and absorption (m and d)

36

opioids uses

Anti-secretory activity against cholera toxin. Effective against traveler’s diarrhea, alone or with antibiotics - discontinue if no improvement in 48 hours

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opioid side effects

low addiction (low solubility), overdose can cause CNS depression and paralytic ileus

38

Polycarbophil MOA

binds free fecal water

39

polycarbophil uses

•Useful in diarrhea (absorbs 60X weight in H2O) and constipation (prevents fecal desiccation)

40

List Absorbent Agents

Bismuth, Kaolin / Pectin

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absorbent agent uses

manages mild/moderate diarrhea by adsorbing toxins that cause irritation.

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absorbent agents side effects

•Avoid use of bismuth subsalicylate in children under 12 y/o (salicylate risk for Reye’s syndrome)

43

List Drugs for IBS

Tegaserod (for constipation), Alosetron (for diarrhea)

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Alosetron MOA

seretonin 5Ht3 antagonist- Block of 5-HT3 receptors on sensory and motor neurons reduces pain and inhibits colonic motility

45

alosetron uses

Severe IBS in women with diarrhea as the prominent symptom - restricted use due to risk of ischemic colitis

46

Tegaserod MOA

Serotonin 5-HT4 Agonist > release of NTs > peristaltic reflex > gastric empyting and intestinal motility

47

Tegaserod uses

IBS patients with predominant constipation

48

tegaserod side effects

•heart attacks, strokes, and unstable angina leading to restricted use