Lecture 15 - OTC Digestion Flashcards
there are a number of common maladies that can afflict the GI tract, including:
- peptic ulcers
- gastroesophageal reflux disease (GERD)
- nausea and vomiting
- GI motility prblems (constipation and diarrhea)
a group of disorders involving either excessive acid secretion or erosion of the mucosal lining of the GI tract (particularly the stomach)
acid-peptic diseases
the stomach is divided into the:
antrum (bottom) and fundus (top)
cells in the fundus of the stomach responsible for acid secretion (H+ ions)
parietal cells
moves acid from the parietal cell into the gastric lumen
the H+/K+ ATPase proton pump
cells in the antrum that respond to intraluminal dietary peptides to release gastrin
G-cells
gastrin binds to:
cholecystokinin (CCK) receptors on parietal cells
gastrin stimulates ______ to release ______ which binds to ______ on parietal cells
enterochromaffin cells (H cells), histamine, histamine (H2) receptors
the vagus nerve stimulates postganglionic neurons of the enteric nervous system to release ______, which binds to ______ on parietal cells
acetylcholine, muscarinic receptors (M3)
cells which release somatostatin and inhibit gastrin release from G cells
D cells
what causes D cells to release somatostatin?
an increase in intraluminal acid
what effect does excess acid production have on the stomach?
it erodes the mucosal barrier
loss of sphincter integrity can lead to:
acid in the esophagus
most OTC treatment for peptic ulcer disease are focused on:
controlling acid production in the stomach (antacids and proton pump inhibitors)
weak bases that neutralize stomach acid by reacting with protons in the lumen of the gut
antacids
popular antacids include:
magnesium hydroxide (Mg[OH]2) and aluminium hydroxide (Al[OH]3)
when used regularly, in the large doses required to raise stomach pH, antacids reduce the:
recurrence rate of peptic ulcers
magnesium hydroxide has a strong:
laxative effect
aluminium hydroxide has a:
constipating action
lipophilic weak bases that diffuse into the parietal cell and inactivate the H+/K+ ATPase transporter
proton pump inhibitors (ex: Omeprazole)
prolonged use of proton pump inhibitors can lead to:
hypergastrinemia
proton pump inhibitors will decrease the bioavailability of:
vitamin B12 and certain drugs that require acidity for their absorption
nausea and vomiting is an important defence against:
food poisoning
can help when dealing with nausea and vomiting caused by motion sickness caused by other conditions
OTC anti-emetics
the active ingredient in PeptoBismol
bismuth subsalicylate
bismuth subsalicylate hydrolyzes in the gut to:
bismuth oxychloride and salicylic acid
salicylic acid is absorbed in the gut and:
inhibits prostaglandin synthesis (anti-inflammatory properties)
bismuth salts are not absorbed from the gut, but have:
bactericidal effects
dimenhydrinate (gravol) is a theoclate salt composed of:
diphenhydramine and 8-chlorotheophylline
dimenhydrinate acts as a ______ at the ______ receptor
competitive antagonist/inverse agonist, H1
what is the effect of 8-chlorotheophylline?
reduces potency of dimenhydramine
what is the effect of dimenhydrinate?
blocks histamine activity in the vestibular system, but less sedation than diphenhydramine (less potent)
GI motility is controlled by:
intrinsic neural plexuses (enteric nervous system)
removing extrinsic autonomic control of the GI tract results in:
disorganized gastric activity (nausea and vomiting)
the enteric nervous system is also known as the:
“second brain”
enteric neurons are organized into a:
nerve plexus
provides motor innervation to the muscular layer of the gut (mediates peristalsis)
myenteric plexus
provides secretomotor (inducing a gland to secrete a substance) innervation to the gut mucosa
submucosal plexus
the neurons of the myenteric plexus and submucosal plexus are predominantly:
cholinergic
all preganglionic neurons in the autonomic nervous system are:
cholinergic
postganglionic parasympathetic neurons are:
cholinergic
postganglionic sympathetic neurons are:
adrenergic
preganglionic parasympathetic neurons release acetylcholine onto postganglionic neurons within:
myenteric neurons within the stomach and upper intestine
binds to muscarinic receptors (M2) on GI smooth muscle leading to contraction
acetylcholine
acetylcholine stimulates the production of:
acid from parietal cells
adrenergic postganglionic sympathetic fibers innervate:
enteric neurons (both myenetric and submucosal plexus)
what effect do adrenergic postganglionic sympathetic fibers have on gut motility?
inhibits gut motility
occurs when bowel movements become less frequent and stools are difficult to pass
constipation
substances that loosen stool or stimulate bowel movement
laxatives
what are the four major kinds of laxatives?
- bulk forming laxatives
- osmotic laxatives
- lubricant laxative
- stimulate laxatives
contain naturally occuring plant fiber like psyllium and methyl cellulose that draw water into the stool to make them larger and easier to pass (must drink lots of water while taking)
bulk forming laxatives
contain ingredients like polyethylene glycol or magnesium that draw fluid into the bowel from nearby tissue
osmotic laxatives
glycerin suppositories (mineral oil) that coat the surface of stools or anus to make it easier for stools to pass
lubricant laxatives
contain ingredients like senna and bisacodyl that cause the bowels to squeeze out the stools
stimulant laxatives
loose, watery stool that occurs when the colon is unable to adequately absorb the liquid from ingested food/fluid
diarrhea
diarrhea is usually caused by:
a bacterial or viral infection
what is the most common OTC treatment for diarrhea?
loperamide and bismuth subsalicylate
loperamide is a:
mu opioid agonist
where in the GI tract are mu opioid receptors located?
on the myenteric plexus (controls peristalsis)
true or false: loperamide has weak analgesic activity despite being a full agonist at the mu opioid receptor
true
where is loperamide distributed to?
loperamide is widely distributed across the body, including the brain
what makes lopermaide different from codeine?
less analgesia, less respiratory depression, no effect on cough
loperamide is a substrate for:
P-glycoprotein (P-gp)
where is P-glycoprotein (P-gp) located?
endothelial cells at the blood brain barrier (actively pumps drugs out of the brain)
why isn’t loperamide rewarding/addictive like morphine?
loperamide brain levels are kept low by P-gp activity
P-glycoprotein (P-gp) is inhibited by:
tricyclic antidepressants (amitriptyline)
blockin P-glycoprotein (P-gp) will increase brain concentration of:
loperamide
