Motility Disorders

Question 1

What are prokinetic agents?

Answer 1

Drugs that selectively stimulate gut motor fxn

Question 2

What is the action of intrinsic primary afferent neurons (IPANs)?

Answer 2

Activate enteric neurons responsible for peristalsis & secretory reflex

Question 3

What action enhances the release of Ach & calcitoningene-related peptide, promoting reflex activity?

Answer 3

Stimulation of 5-HT4 receptors on presynaptic terminals of IPANs

Question 4

What are cholinomimetic agents used for?

Answer 4

GERD
Impaired gastric emptying
Nonulcer dyspepsia
Prevention of vomiting

Question 5

What cholinoimetic agent is NOT approved by FDA or available in the US?

Answer 5

Domperidone (pospartum lactation stimulation)

Question 6

What are ADEs of metoclopramide?

Answer 6

Extrapyramidal effects
Tardive dyskinesia
Elevated prolactin

Question 7

What is the MOA of erythromycin (a macrolide)?

Answer 7

Stimulate motilin receptors

Question 8

How do you treat a patient w/ constipation who has no underlying dx?

Answer 8

Symptomatic therapy

Question 9

List the laxative agents (8)

Answer 9

Bulk forming 
Stool surfactant (softeners)
Osmotic 
Stimulant 
Chloride channel activator
Guanylate cyclase c activator
Opioid receptor antagonists
Serotonin 5-HT4 agonists

Question 10

What 3 agents result in soft or semifluid stool in 6-12 hrs?

Answer 10

Bisacodyl (oral)
Senna
Mg sulfate (low dose)

Question 11

What 6 agents cause watery evacuation in 1-6 hrs?

Answer 11

Mg citrate
Mg hydroxide
Mg sulfate (high dose)
Na phosphates 
Bisacodyl (rectal)
PEG

Question 12

What are 2 common preparations of bulk forming laxatives?

Answer 12

Natural plant products:

Psyllium
Methylcellulose

Question 13

What is an example of a stool surfactant agent?

Answer 13

Docusate (oral or enema)

Question 14

What can mineral oil cause?

Answer 14

Aspiration –> severe lipid pneumonitis

Question 15

What are examples of osmotic laxatives?

Answer 15

Mg hydroxide (Milk of Mag)

Sorbitol & lactulose

Question 16

What is the MOA of stimulant laxatives?

Answer 16

Direct stimulation of the enteric NS

Question 17

Cathartics may be required on a _______

Answer 17

long-term basis

Question 18

What are examples of stimulant laxatives?

Answer 18

Anthraquinone derivatives: aloe, senna, cascara

Diphenylmethane derivative:
bisacodyl

Question 19

What are characteristics of bisacodyl (a diphenylmethane derivative)?

Answer 19

Minimal systemic absorption

Appears to be safe for acute & long-term use

Question 20

What are 3 examples of opioid receptor antagonists?

Answer 20

Methylnaltrexone

Alvimopan

Naloxegol

Question 21

What are clinical controversies?

Answer 21

1. Withholding food is considered inappropriate in pts w/ no signs of severe dehydration
2. In osmotic diarrhea, food may control the problem
3. If the mechanism is secretory, diarrhea persists

Question 22

What are examples of antidiarrheal agents?

Answer 22

Opioid agonists:
loperamide, diphenoxylate

Bile salt-binding resins (cholestyramine, colestipol, colesevelam)

Question 23

Colesevelam does not appear to have significant effects on…

Answer 23

absorption of other drugs

Question 24

Describe somatostatin

Answer 24

Antisecretory: octreotide

14-amino-acid peptide released in the GI tract & pancreas from paracrine cells, D cells, enteric nerves, & the hypothalamus

Question 25

What is the MOA of somatostatin?

Answer 25

Inhibits the secretion of numerous hormones & transmitters Reduces intestinal fluid secretion & pancreatic secretion Slows GI motility & inhibits gallbladder contraction

Question 26

What do GI neuroendocrine tumors cause? What inhibits this?

Answer 26

Secretory diarrhea Antisecretory: octreotide

Question 27

What are ADEs of octreotide?

Answer 27

Steatorrhea Nausea, abd pain, flatulence, diarrhea Prolonged tx --> hypothyroidism Brady

Question 28

What is the MOA of metoclopramide?

Answer 28

D2 receptor antagonist Blocks D2 receptors in the trigger zone of the medulla

Question 29

What is the action of metaclopramide?

Answer 29

Increases: - esophageal peristalsis - LES pressure - gastric emptying

Question 30

What is the MOA of bethanechol (a cholinomimetic)?

Answer 30

Stimulates M3 receptors at myenteric plexus synapses

Question 31

What is the MOA of neostigmine (a cholinoimetic)?

Answer 31

Acetylcholinesterase inhibitor

Question 32

What are ADEs of cholinomimetics?

Answer 32

Salivation, N/V/D, brady

Question 33

Which types of laxative cause softening of feces in 1-3 days?

Answer 33

Bulk-forming Emollients (softeners) PEG

Question 34

What are 2 examples of purgatives (laxatives)?

Answer 34

Mg citrate & Na phosphate

Question 35

What are ADEs of anthraquinone derivatives: aloe, senna, & cascara?

Answer 35

Melanosis coli Concern that these agents may be carcinogenic, but studies do not suggest relation

Question 36

What is alvimopan (an opioid receptor antagonist) used for?

Answer 36

shortens the period of postop ileus in hospitalized pts who undergo small or large bowel resection

Question 37

What are 3 adsorbents?

Answer 37

Kaolin-pectin Polycarbophil Attapulgite