lower GI pharmacology

Question 1

anti-emetics for cancer chemo

Answer 1

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

Question 2

anti-emetics for pregnancy

Answer 2

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

Question 3

list 5HT3 receptor antagonists

Answer 3

Ondansetron

Question 4

5HT3 antagonists uses

Answer 4

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

Question 5

list Dopamine (D2) receptor antagonists

Answer 5

Prochloroperazine , Metoclopramide (also blocks 5HT3)

Question 6

dopamine antagonist side effects

Answer 6

Extrapyramidal symptoms (movement disorders)

Question 7

dopamine antagonist uses

Answer 7

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

Question 8

List Antihistamines (1st generation)

Answer 8

Meclizine, promethazine, Diphenhydramine (dimenhydrinate)

Question 9

antihistamine uses

Answer 9

motion sickness and postoperative emesis

Question 10

list Anticholinergic agents

Answer 10

Scopolamine

Question 11

Anticholinergic agents uses

Answer 11

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

Question 12

Anticholinergic agents pharmacokinetics

Answer 12

transdermal- duration of action 72 hrs

Question 13

Which drugs can induce constipation

Answer 13

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

Question 14

List Bulk-forming / fiber laxatives

Answer 14

Psyllium Seed (metamucil)

Question 15

Fiber uses and MOA

Answer 15

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

Question 16

Fiber pharmacokinetics

Answer 16

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

Question 17

List Saline (osmotically-active) cathartics

Answer 17

Mg(OH)2, Polyethylene glycols, lactulose

Question 18

Saline (osmotically-active) cathartics uses

Answer 18

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

Question 19

Saline (osmotically-active) cathartics MOA

Answer 19

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

Question 20

Saline (osmotically-active) cathartics pharmacokinetics

Answer 20

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.

Question 21

List Stimulant / irritant laxatives

Answer 21

Bisacodyl (dulcolax)

Question 22

Stimulant / irritant laxatives uses

Answer 22

used for constipation if fiber/saline fails.

Question 23

Bisacodyl MOA

Answer 23

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

Question 24

Bisacodyl side effects

Answer 24

electrolyte / fluid deficiencies, severe cramping

Question 25

List Wetting agents / emollient laxatives

Answer 25

Docusate (ex lax extra gentle)

Question 26

Ducosate MOA

Answer 26

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

Question 27

Ducosate uses

Answer 27

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

Question 28

List meds used for opioid induced constipation

Answer 28

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

Question 29

two causes of diarrhea

Answer 29

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

Question 30

Causes of osmotic diarrhea

Answer 30

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

Question 31

causes of secretory diarrhea

Answer 31

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

Question 32

drugs that can induce diarrhea

Answer 32

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

Question 33

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

Answer 33

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

Question 34

List antidiarrheal Opioids

Answer 34

Loperamide

Question 35

opioids MOA

Answer 35

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

Question 36

opioids uses

Answer 36

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

Question 37

opioid side effects

Answer 37

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

Question 38

Polycarbophil MOA

Answer 38

binds free fecal water

Question 39

polycarbophil uses

Answer 39

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

Question 40

List Absorbent Agents

Answer 40

Bismuth, Kaolin / Pectin

Question 41

absorbent agent uses

Answer 41

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

Question 42

absorbent agents side effects

Answer 42

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

Question 43

List Drugs for IBS

Answer 43

Tegaserod (for constipation), Alosetron (for diarrhea)

Question 44

Alosetron MOA

Answer 44

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

Question 45

alosetron uses

Answer 45

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

Question 46

Tegaserod MOA

Answer 46

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

Question 47

Tegaserod uses

Answer 47

IBS patients with predominant constipation

Question 48

tegaserod side effects

Answer 48

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