Motility Disorders Flashcards
What are prokinetic agents?
Drugs that selectively stimulate gut motor fxn
What is the action of intrinsic primary afferent neurons (IPANs)?
Activate enteric neurons responsible for peristalsis & secretory reflex
What action enhances the release of Ach & calcitoningene-related peptide, promoting reflex activity?
Stimulation of 5-HT4 receptors on presynaptic terminals of IPANs
What are cholinomimetic agents used for?
GERD
Impaired gastric emptying
Nonulcer dyspepsia
Prevention of vomiting
What cholinoimetic agent is NOT approved by FDA or available in the US?
Domperidone (pospartum lactation stimulation)
What are ADEs of metoclopramide?
Extrapyramidal effects
Tardive dyskinesia
Elevated prolactin
What is the MOA of erythromycin (a macrolide)?
Stimulate motilin receptors
How do you treat a patient w/ constipation who has no underlying dx?
Symptomatic therapy
List the laxative agents (8)
Bulk forming Stool surfactant (softeners) Osmotic Stimulant Chloride channel activator Guanylate cyclase c activator Opioid receptor antagonists Serotonin 5-HT4 agonists
What 3 agents result in soft or semifluid stool in 6-12 hrs?
Bisacodyl (oral)
Senna
Mg sulfate (low dose)
What 6 agents cause watery evacuation in 1-6 hrs?
Mg citrate Mg hydroxide Mg sulfate (high dose) Na phosphates Bisacodyl (rectal) PEG
What are 2 common preparations of bulk forming laxatives?
Natural plant products:
Psyllium
Methylcellulose
What is an example of a stool surfactant agent?
Docusate (oral or enema)
What can mineral oil cause?
Aspiration –> severe lipid pneumonitis
What are examples of osmotic laxatives?
Mg hydroxide (Milk of Mag)
Sorbitol & lactulose
What is the MOA of stimulant laxatives?
Direct stimulation of the enteric NS
Cathartics may be required on a _______
long-term basis
What are examples of stimulant laxatives?
Anthraquinone derivatives: aloe, senna, cascara
Diphenylmethane derivative:
bisacodyl
What are characteristics of bisacodyl (a diphenylmethane derivative)?
Minimal systemic absorption
Appears to be safe for acute & long-term use
What are 3 examples of opioid receptor antagonists?
Methylnaltrexone
Alvimopan
Naloxegol
What are clinical controversies?
- Withholding food is considered inappropriate in pts w/ no signs of severe dehydration
- In osmotic diarrhea, food may control the problem
- If the mechanism is secretory, diarrhea persists
What are examples of antidiarrheal agents?
Opioid agonists:
loperamide, diphenoxylate
Bile salt-binding resins (cholestyramine, colestipol, colesevelam)
Colesevelam does not appear to have significant effects on…
absorption of other drugs
Describe somatostatin
Antisecretory: octreotide
14-amino-acid peptide released in the GI tract & pancreas from paracrine cells, D cells, enteric nerves, & the hypothalamus
What is the MOA of somatostatin?
Inhibits the secretion of numerous hormones & transmitters
Reduces intestinal fluid secretion & pancreatic secretion
Slows GI motility & inhibits gallbladder contraction
What do GI neuroendocrine tumors cause?
What inhibits this?
Secretory diarrhea
Antisecretory: octreotide
What are ADEs of octreotide?
Steatorrhea
Nausea, abd pain, flatulence, diarrhea
Prolonged tx –> hypothyroidism
Brady
What is the MOA of metoclopramide?
D2 receptor antagonist
Blocks D2 receptors in the trigger zone of the medulla
What is the action of metaclopramide?
Increases:
- esophageal peristalsis
- LES pressure
- gastric emptying
What is the MOA of bethanechol (a cholinomimetic)?
Stimulates M3 receptors at myenteric plexus synapses
What is the MOA of neostigmine (a cholinoimetic)?
Acetylcholinesterase inhibitor
What are ADEs of cholinomimetics?
Salivation, N/V/D, brady
Which types of laxative cause softening of feces in 1-3 days?
Bulk-forming
Emollients (softeners)
PEG
What are 2 examples of purgatives (laxatives)?
Mg citrate & Na phosphate
What are ADEs of anthraquinone derivatives: aloe, senna, & cascara?
Melanosis coli
Concern that these agents may be carcinogenic, but studies do not suggest relation
What is alvimopan (an opioid receptor antagonist) used for?
shortens the period of postop ileus in hospitalized pts who undergo small or large bowel resection
What are 3 adsorbents?
Kaolin-pectin
Polycarbophil
Attapulgite
