OTC Digestion Flashcards
what are 4 common maladies of the GI tract that can be treated w OTC drugs?
peptic ulcers, gastroesophageal reflux disease (GERD, heartburn), nausea/vomiting, GI motility problems (constipation, diarrhea)
what are acid-peptic diseases?
excessive acid secretion or erosion of mucosal lining of GI tract (GERD, peptic ulcers, gastritis)
what do drugs that treat acid-peptic diseases do? (3)
decr GI acidity by decr acid secretion, incr mucosal defense, or eradicate H. pylori
what bacteria is associated with peptic ulcers?
Helicobacter pylori (breaks down mucosal barrier)
what drugs can cause peptic ulcers?
NSAIDs
what cells in the stomach secrete H+?
parietal cells (in the fundus)
what are the 2 regions of the stomach?
fundus (top) and antrum (bottom)
what pump do parietal cells use to make the stomach acidic?
H+/K+ ATPase pump (H+ against conc. grad.)
what 3 compounds control acid production from parietal cells?
gastrin, histamine, acetylcholine
how does gastrin stimulate acid production from parietal cells?
G cells in antrum detect protein/a.a. and release gastrin which binds to CCK receptors on P cells
how does histamine stimulate acid production from parietal cells?
gastrin stimulates enterochromaffin cells (H cells) in fundus to release histamine which binds to H2 receptors on P cells
how does ACh stimulate acid production from parietal cells?
vagus nerve (parasymp.) stimulates postgang. neurons of ENS to release ACh which binds to muscarinic (M3) receptors on P cells
what is the negative feedback loop to decr acid production from P cells?
D cells in antrum detect low pH (<3) and release somatostatin which inhibits gastrin release from G cells
what are the dangers of excess acid production in stomach?
erodes mucosal layer and LES
what can lead to acid in eso. (GERD)?
loss of LES integrity (from pregnancy, obesity, etc.)
what are antacids?
weak bases that neutralize stomach acid by reacting w H+
what are antacids used to treat?
peptic ulcers (decr recurrence rate if taken frequently and in high doses)
what are 2 popular antacids?
magnesium hydroxide (Mg[OH]2) and aluminum hydroxide (Al[OH]3)
what are the diff side effects of Mg(OH)2 and Al(OH)3?
(both not absorbed from bowel)
Mg(OH)2: laxative effect
Al(OH)3: constipation action
what are proton pump inhibitors?
lipophilic weak bases that diffuse into P cells and inactivate H+/K+ ATPase
what is an example of a proton pump inhibitor?
Omeprezole
what can prolonged use of proton pump inhibitors cause?
hypergastrinemia (acid secretion inhibits gastrin) which can incr cancer risk
what is a side effect of proton pump inhibitors?
decr bioavailability of vit B12 or other drugs that require acidity to be absorbed
what are OTC drugs called that treat nausea and vomiting caused by motion sickness or other conditions?
antiemetics
what is bismuth subsalicylate?
antiemetic, active ingredient in Pepto Bismol
what happens to bismuth subsalicylate in the stomach?
hydrolyzes to bismuth oxychloride (salt) and salicylic acid
what does salicylic acid do (from bismuth subsalicylate)?
is absorbed by gut and acts as a COX2 inhibitor (anti-inflammatory)
what do bismuth salts do (from bismuth subsalicylate)?
not absorbed by gut but has antibacterial effects (can bind to toxins from E. Coli and H. pylori)
what are 3 other effects of bismuth subsalicylate?
weak antacid properties, slows gut motility, stimulates fluid absorption
what is dimenhydramine?
competitive antagonist at H1 receptor (active ingr in Gravol)
what does dimenhydramine do?
block histamine activity in vestibular system
what is the ENS?
intrinsic neural plexuses that control GI motility (= second brain)
what modulates ENS?
CNS and ANS (para: vagus nerve and symp)
what results from removing extrinsic ANS control from ENS?
disorganized gastric activity but returns to normal over time (by ENS)
what are the 2 plexuses of the ENS?
myenteric and submucosal
what does the myenteric plexus do?
provide motor innervation to muscular layer of gut (peristalsis)
what does the submucosal plexus do?
provide secretomotor innervation to submucosa (induce gland to produce mucus)
what type of neurons are in the ENS plexuses primarily?
cholinergic (also has serotonin and dopamine)
what do pregang ANS neurons release?
ACh (cholinergic)
what do postgang ANS neurons release?
para: ACh (cholinergic)
symp: NA (adrenergic)
what do pregang parasym neurons innervate?
postgang myenteric muscarinic (ACh) neurons in eso, stomach, and upper intest
what does ACh binding to GI smooth muscle cause?
contraction (motility)
what does vagus release of ACh also stimulate?
acid production from parietal cells
what do postgang symp neurons innervate?
adrenergic myenteric and submucosal enteric neurons in intes and colon
what receptors does NA from postgang symp neurons bind to?
alpha2 adrenergic receptors
what is effect of sympathetic innervation of the GI tract?
inhibition of gut motility
what is constipation?
less frequent bowel movements that are more difficult to pass
what causes contipation?
low fiber diet and decr water intake
what are laxatives?
substances that loosen stool or stimulate bowel movements
what are 4 kinds of laxatives?
bulk-forming, osmotic, lubricant and stimulant
what do bulk-forming laxatives do?
draw water into stool to make them larger and easier to pass by containing plant fibers such as psyllium and methyl cellulose (must take w/ water)
what do osmotic laxatives do?
draw fluid into bowel from nearby tissues by containing polyethylene and Mg
what do lubricant laxatives do?
coat surface of stool or anus to make it easier for stools to pass by containing glycerin suppositories (mineral oil)
what do stimulant laxatives do?
cause bowels to squeeze stool out by containing senna and bisacodyl
what is diarrhea?
loose, watery stool as colon doesn’t absorb fluid from food
what causes dairrhea?
bacterial or viral infections
what are 2 common OTC treatments for diarrhea?
loperamide and bismuth subsalicylate
what is loperamide?
full mu opioid agonist
where are mu opioid receptors in GI tract?
submucosal and myenteric (mainly) plexus
what are mu opioid receptors?
Gi GPCRs
what does loperamide do?
binds to mu opioid receptors to slow peristalsis and inhibit secretion of water and mucus
what is different btwn loperamide and other opioid agonists?
has weak analgesic effects (not rewarding/addicting, no resp depression)
why can’t loperamide cause any physiological effects in the brain?
is a substrate for P-gp (permeability-glycoprotein), which is a pump in the endothelial cells of the BBB that actively removes drugs from the brain
what drugs interfere with P-gp?
tricyclic antidepressants (amitriptyline)
what are some adverse effects of taking amitriptyline with loperamide?
respiratory depression and abuse as amitriptyline blocks P-gp allowing [loperamide] in brain to incr
why are some OTC drugs for common digestive problems counterproductive?
bacterial or viral infections should be removed through vomiting/anal/urethral excretion
Mucosal surface cells secrete mucous that provides a barrier btwn __________ and __________
Mucosa (top layer of stomach) and lumen
what kind of receptors are alpha2 adrenergic receptors?
Gi GPCR
