How much Water normally accounts for the total stool weight?
70% to 85%
How does the gut form a manageable pool of fluid for proper expulsion of waste material via the process of defecation?
extract water, minerals, and nutrients from the luminal contents
The colon recaptures all electrolytes except?
K+,
What is the definition constipation for most people?
Decreased frequency, Difficulty in initiation or passage, Passage of firm or small-volume feces, A sense of incomplete evacuation
Name the two types of colonic motility and their function?
Nonpropulsive contractions, mixing luminal contents to promote absorption of water, Propulsive contractions, which propagate caudally over extended lengths in the colon and evoke mass transfer of feces from the right to the left colon once or twice a day.
T/F: Decreased motility of the nonpropulsive type and Increased motility of the mass action type may lead to constipation.
False: it is opposite
What are the three actions of laxatives?
Enhancing retention of intraluminal fluid by hydrophilic or osmotic mechanisms, -Decreasing net absorption of fluid by effects on small- and large-bowel fluid and electrolyte transport, -Altering motility by either inhibiting segmenting (nonpropulsive) contractions or stimulating propulsive contractions.
Which classes of laxatives produce results within the following clinical time periods: 1-3 days, 6-8 hours, and 1-3 hours?
1-3 days: Bulk-forming and surfactant laxatives, 6-8 hours: Stimulant and Anthraquinone derivative laxatives, 1-3 hours: Osmotic laxatives
How do dietary fibers help with constipation?
It adds bulk because it resists enzymatic digestion and reaches the colon largely unchanged
What effects of colonic bacterial fermentation of fiber have on constipation?
It produces short-chain fatty acids that are trophic for colonic epithelium, - It increases bacterial mass.
What is the recommended fiber intake for a person with constipation? How much does water intake help?
20-40 g/day
What is the effect of non-fermented fiber?
attacts water to increase stool bulk and invoke propulsion
T/F: Lignin and cellulose are not as effective as Pectins and Hemicelluloses in stool transit.
False: it is opposite
T/F: Lignin and cellulose are not as effective as Pectins and Hemicelluloses in propagation of bacterial growth.
TRUE
The net effect of fruits and vegetables for colonic motility is?
increasing colonic bacterial mass because Fruits & vegetables contain more pectins & hemicelluloses
Psyllium husk (from the Planago ovata herb) undergoes significant fermentation in colon, leading to an increase in colonic bacterial mass because it contains __________.
hydrophilic mucilloid
What are some poorly fermented compounds (OTC)used for constipation?
What three conditions are contindicated with Dietary Fibers?
with obstructive symptoms, with megacolon or megarectum
What is the common S/E of soluble fiber products?
Bloating that usually decreases with time
Which patients should avoid the usage of a Calcium Polycarbohhil preparation?
patients who must restrict their intake of calcium since they release Ca2+ in the GI tract
What condition is contraindicated with the use of Sugar-Free bulk laxatives? Why?
patients with phenylketonuria because they may contain aspartame which contains phenylalanine
What is the risk, in women with phenylketonuria, if phenylalanine levels are not strictly controlled before and during pregnancy?
their offspring are at risk for congenital defect and microcephaly (maternal phenylketonuria)
Phenylaketonuria is the results if _______________does not convert _______________ to ___________ used as a precurser for nuerotransmitters.
Phenylalanine Hydroxylase
How do lactulose, sorbitol, and mannitol stimulate colonic propulsive motility?
hydrolyzed in colon to short-chain fatty acids
Non-digestible sugars/alcohols are efficacious in treatment of which 3 types of constipation?
constipation caused by opioids and vincristine, constipation in the elderly, idiopathic chronic constipation
Lactulose (CEPHULAC, CHRONULAC) is a synthetic disaccharide of galactose & fructose that resists_______.
intestinal disaccharidase activity
What are the two stool-wetting/emollient agents?
Docusate sodium (diocytl sodium sulfosuccinate
How do stool-wetting/emollient agents help with constipation?
They are Anionic Surfactants �lower surface tension of the stool to allow mixing of aqueous and fatty substances, softening the stool and permitting easier defecation, -Stimulate intestinal fluid & electrolyte secretion possibly by ? cAMP and alter intestinal mucosal, -Have marginal efficacy in most cases of constipation.
Diphenylmethane derivatives, anthraquinones, and ricinoleic acid are examples of which class of laxatives?
stimulant Laxatives
Stimulant laxatives have a direct effect on which 3 types of cells in the GIT?
enterocytes, enteric neurons, and GI smooth muscle
MOA of Stimulant Laxatives:
Activation of prostaglandin� cAMP and NO� cGMP pathways, Induce a limited low-grade inflammation in small & large bowel to promote accumulation of water and electrolytes and stimulate intestinal motility, Platelet-activating factor production
Bisacodyl (Dulcolax, Correctol) is an example of which class of laxatives? How is it activated?
Diphenylmethane Derivatives
Bisacodyl is mainly excreted in the stool
about 5% is absorbed and excreted in the urine as a ___________.
Side Effects and precautions for bisacodyl:
Can damage the mucosa and initiate an inflammatory response in the small bowel and colon, Overdosage can lead to catharsis and fluid and electrolyte deficits
Anthraquionone laxatives share a tricyclic anthrancene nucleus that form ______________which is the active form.
monoanthrones
Aging or drying converts monoanthrones to what type of glycoside? How is it converted back to the active form?
a more innocuous dimeric (dianthrones) glycosides
What effect do anthraguinone laxatives produce?
Produce giant migrating colonic contractions and induce water and electrolyte secretion
A melanotic pigmentation of the colonic mucosa (melanosis coli) has long periods (? 4-9 mo.) , Caused by the presence of pigment-laden macrophages within the lamina propria, Cathartic colon, which can be seen in patients (typically women) who have a long-standing history (typically years) of laxative abuse
