PHARM_GI

Question 1

How do the bulk forming laxatives work?

Answer 1

increase delivery of water to colon, decrease pressure in sigmoid colon, net result is more formed stools

Question 2

how does docusate (colace) work?

Answer 2

anionic surfactant, stool softener, used to reduce strain of defecation

Question 3

what are the adverse effects of docusate (colace)?

Answer 3

can irritate the intestinal mucosa & increase intestinal absorption of other drugs (use only short term)

Question 4

how does castor oil work?

Answer 4

surfactant laxative that is rapid acting and effective anionic surfactant that produces catharsis, stimulates intestinal peristalsis

Question 5

what are the AEs of castor oil?

Answer 5

colic
dehydration
electrolyte imbalance with overdose
can induce uterine contraction in pregnant women

Question 6

on what part of the GI tract do the stimulant laxatives work on?

Answer 6

mostly large bowel

Question 7

how do stimulant laxatives work?

Answer 7

• increase permeability of intestinal mucosa
• increase back diffusion of water and electrolytes
• increase propulsive contractility of colon by stim. colonic myenteric plexus
• stimulate PG synth. & increase intestinal secretions

Question 8

what is the most potent class of laxatives?

Answer 8

stimulant laxatives

Question 9

name the stimulant laxatives

Answer 9

diphenylmethanes (bisacodyl)

anthraquinones (senokot)

Question 10

bisacodyl (dulcolax) MOA

Answer 10

prodrug that is converted by enteric bacteria into the desacetyl active form, acts as stimulant laxative

Question 11

anthraquinones (senokot) MOA

Answer 11

stimulant laxative that is natural derivatives of senna plant, more gentle than synthetic drugs
-act by promoting colonic motility

Question 12

what happens if you overdose on bisacodyl?

Answer 12

can cause excessive fluid & electrolyte loss, intestinal enterocyte damage leading to colonic inflammatory response

Question 13

large doses of anthraquinones (senokot) can cause what?

Answer 13

can cause abd. pain, nephritis, melanotic pigmentation of colonic mucosa, abnormal color of urine

Question 14

what is GOLYTELY used for?

Answer 14

Polyethylene glycol electrolyte soln used for colonoscopy for complete evacuation

Question 15

name the 2 laxatives used in IBS

Answer 15

lubiprostone

linaclotide

Question 16

how does lubiprostone work?

Answer 16

activates Cl- channels (in PKA independent fashion), increases intestinal fluid secretion and motility and alleviates the symptoms associated with chronic idiopathic constipation (used in IBS for constipation)

Question 17

what are the 3 different kinds of antidiarrheal agents?

Answer 17

1. agents that absorb water (metamucil)
2. adsorbers of etiologial factors in the lumen (e.g. pepto-bismol)
3. agents that alter intestinal motility (opiates)

Question 18

how does bismuth subsalicylate work?

Answer 18

adsorb harmful bacteria, viruses, or toxin

Question 19

what drug is an effective treatment for preventing Traveler’s diarrhea and also treats H. pylori infections?

Answer 19

bismuth subsalicylate

Question 20

how do opiates work as antidiarrheal agents?

Answer 20

decrease salivary, gastric, & intestinal gland secretions
decrease motility of the stomach & intestines
increase muscle tone
increase tone of muscle sphincters including EAS “reduces urgency”
The overall effect is increasing the contact time between ingested matter and the reabsorbtive intestinal epithelium

Question 21

this drug interacts with intestinal opioid receptors and binds to & inhibits the calcium binding protein calmodulin

Answer 21

loperamide (anti-diarrheal)

Question 22

what is the purpose of using anticholinergics as antidiarrheal agents?

Answer 22

used for this b/c they are anti-spasmodic

Question 23

what drug is prophylactic only for motion sickness arising from short or long exposure to severe motion

Answer 23

scopolamine

Question 24

scopolamine MOA

Answer 24

scopolamine is anticholinergic that blocks the activation of muscarinic receptors to ACh. (Cochlear sensation of motion is projected via cholinergic fibers of the auditory nerve to the CTZ)

Question 25

how is scopolamine administered?

Answer 25

patch placed near ear

Question 26

what are some of the side effects of using scopolamine?

Answer 26

sedation, drowsiness, dry mouth

Question 27

which antidopaminergic blocks therapeutic induced activation of D2 receptors in the CTZ? Also inhibits gastric emptying

Answer 27

metoclopramide

Question 28

how do H1 antihistamines work in the treatment of motion sickness?

Answer 28

older H1 antihistamines also have anticholinergic effects

Question 29

name the 2 piperazines that are H1 antihistamines

Answer 29

cyclizine (OTC) | meclizine

Question 30

which H1 antihistamine has a depressant effect on hyperstimulation of labyrinthine function and is used for vestibular disturbances?

Answer 30

meclizine

Question 31

how are antidopaminergics effective antiemetics?

Answer 31

they block dopamine receptors in the trigger zone (CTZ)

Question 32

which drug is a centrally acting anticholinergic as well as antidopaminergic and is used for N/V & intractable hiccups?

Answer 32

chlorpromazine

Question 33

which antidopaminergic drug blocks receptors in the CTZ and is clinically used post-op for N/V?

Answer 33

droperidol

Question 34

which antiemetic antidopaminergic drug is given prophylactically to chemo pts to prevent post-op nausea and vomiting?

Answer 34

metoclopramide

Question 35

how are serotonin antagonists effective antiemetics?

Answer 35

5-HT antagnoists block 5-HT3 receptors in the stomach and small intestines -block 5-HT3 receptors in the CTZ that are intimately involved in stimulating the VC to produce emesis

Question 36

which class of antiemetics are the most effective to date?

Answer 36

5-HT antagonists

Question 37

which drug is more potent than ondansetron?

Answer 37

granisetron (anti-emetic)

Question 38

which 5-HT3 antagonist has the longest half life?

Answer 38

dolasetron (anti-emetic)

Question 39

what is the purpose of using corticosteroids, dronabinol, benzodiazepine or aprepitant, in addition to a classic antiemetic drug?

Answer 39

these 3 are used to increase the potency of antiemetic drugs and reduce the dose of each individual agent and also reduce the significance of their combined side effects

Question 40

which drug is a substance P/ NK1 receptor antagonist?

Answer 40

aprepitant (anti-emetic)

Question 41

which drug is used as an adjunct drug for preventing emesis induced by cytotoxic chemotherapy, crosses the BBB & inhibits emesis via central actions

Answer 41

aprepitant (anti-emetic)

Question 42

which class of drugs is used as an adjunct to other antiemetic regimens and is effective for anticipatory vomiting bc they cause somnolence & amnesia lasting for hours?

Answer 42

benzodiazepines

Question 43

which class of drugs is considered the foundation for antiemetic therapy?

Answer 43

5-HT3 receptor antagonist