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What is diarrhea? Can diarrhea be healpful to the patient? Can diarrhea be harmful to the patient?
passage of loose or liquid stools. may be increase in volume or frequency. yes, diarrhea can be helpful - can "wash" out irritants. yes, diarrhea can be harmful - can cause dehydration, weakness, acidosis, anorexia
Name 2 very common causes of diarrhea, that should always be considered first when determining the cause of diarrhea.
Is diarrhea always GI in origin? Do we always have to use drugs to treat diarrhea?
not always GI in origin. no - many simples diarrhea can be managed by NPO, diet.
List 4 basic types (mechanisms) of diarrhea.
- osmotic overload
- increased permeability of intestinal mucosa vessels
- altered intestinal motility.
Many clinical cases of diarrhea are mixed in type, meaning that they have more than 1 mechanism. True or false?
Describe how "osmotic overload" causes diarrhea.
food in the gut is either not broken down into small enough particles, or the particles are not absorbed from the gut into the circulation. the excess particles in the gut pull in or retain water in the guy by osmosis, making the stool more liquid.
What are some of the causes of osmotic overload?
poorly digested food (examples: cow milk - lactose in a lactose intolerant patient); rapid change in diet (normal microbes present in the gut need a little time to adjust); maldigestion/malabsorption (problem with the gut itself. example - infiltrative lymphosarcoma)
Describe how "hypersecretion" can cause dirrhea.
a certain amount of secretion of fluids into the gut is normal. if secretions are excessive, the patient looses too much fluid.
Describe how "increased permeability" of intestinal mucosa blood vessels causes diarrhea.
capillaries in the gut wall are "leaky" due to inflammation, trauma, etc. fluid and, in more severe cases, blood may leak into the gut lumen. example - parvovirus.
List the 2 types of intestinal motility.
peristaltic contractions, segmental contraction
Describe peristaltic contractions. What type of alteration in peristaltic contractions can cause diarrhea?
move gut contents through. increased peristaltic contractions moves gut contents through faster, so there is not enough time for the right amount of fluid to be resorbed.
Describe segmental contractions. What type of alteration in segmental contractions can cause diarrhea?
segmental contraction mix gut contents "in place". decreased segmental contractions means that the gut is more flaccid, and is a wider "pipe" that allows gut contents to move through faster - not enough time for fluid to be properly resorbed.
What types of "altered intestinal motility" can cause diarrhea?
increased peristaltic contractions, decreased segmental contractions
What are antidiarrheal drugs?
drugs used to treat diarrhea
What are the 3 types of antidiarrheal drugs?
drugs that modify intestinal motility, drugs that block hypersecretion, and absorbents and protectants.
List the 2 types of antidiarrrheal drugs that modify intestinal motility.
narcotic or opioid analgesics, anticholinergics
What antidiarrheal effects do opioids ahve on intestinal motility?
increase segmental contractions, decrease peristaltic contractions. longer transit time, more fluid absorption
What other antibiarrheal effect to opioids have?
Opioids are also analgesic. How is it possible for this to be a disadvantage in disease conditions?
may mask signs of pain, cannot follow the progression of the problem as well
When should opioids be used with care?
when we need to monitor signs of pain. in cats and horses.
List 3 narcotic drugs used in antidiarrheals.
- diphenoxylate - Lomotil
- loperamide - Imodium
- paregoric - tincture of opium
WHy is atropine added to diphenoxylate and loperamide?
to discourage abuse - causes unpleasant dryness of the mouth when over-used.
What effect do anticholinergic drugs have on the GI system?
block parasympathetic effects - block secretions, slow down contractions, motility, blood flow, and so on - sympathetic effects.
Are anticholinergics very commonly used to treat diarrhea? Why or why not?
no. most small intestine diarrhea are flaccid or atonic. do not need to decrease contractions any more.
What sort of diarrhea are anticholingerics used for? What do we call anticholinergics when they are used for this purpose?
some spastic colonic diarreha. called "antispasmodics"
List 2 anticholinergics that may be used for certain diarrheas?
- aminopentamide - Centrine
Is atropine used very often for treating diarrhea?
What are the 3 main causes of intestinal hypersecretion leading to diarrhea?
- bacterial enterotoxins
- inflammation with the release of prostaglandins and leukotrienes
- increased parasympathetic stimulation
What are "bacterial enterotoxins"?
toxins released by bacteria in the intestines or toxins released by bacteria that affect the intestines (entero-) - may be ingested.
What types of drugs block hypersecretion?
opioids and anti-inflammatory drugs
List 3 anti-inflammatory drugs or categories of drugs used to block hypersecretory diarrheas.
- flunixin meglumine
What are salicylates? How do salicylate drugs block hypersecretory diarrhea?
salicylates are drugs related to aspirin. they reduce secretions by blocking the formation of prostaglandins
What salicylate drugs fall into the category of anti-inflammatory drugs used to block hypersecretory diarrheas?
bismuth subsalicylate - Pepto-Bismol, Kaopectate (new). (sulfasalzine breaks down to salicylate, also).
Flunixin meglumine - Banamine is mainly used in what species? Why isn't it used in dogs?
- used mostly in horses
- can cause GI ulcers in dogs.
How do absorbents and protectants help in therapy of diarrhea?
by preventing contact of enterotoxins or irritants with the intestinal mucosa.
What is in an "absorbant"? What is an "absorbent"?
- absorbant: a material that attracts and retains other materials on its surface.
- absorbent: a material that takes another material within itself.
List 3 aborbent and protectant drugs.
- activated charcoal
Name an absorbent more commonly used for general therapy of poisoning.
Kaopectate recently (2003) switched from their old, relatively benign and ineffective formulation, very similar to Pepto-Bismol. Why should veterinary professionals be aware of this?
because pet owners may have given the old formulation to their pets in the past, and not realize that they should not give the new formulation to their pets, especially cats (salicylates), without professional advice
Bismuth subsalicylate - Pepto-Bismol and Kaopectate - breaks down into what 2 compounds in the GI tract? How does each of these compounds work against diarrhea?
- bismuth carbonate - protectant, coats GI mucosa. some antimicrobial activity.
- salicylate - like aspirin - antisecretory, blocks formation of prostaglandins to block secretions
Bismuth is similar to waht compound that is used as a contrast material in radiology?
barium - also tends to coat and protect the GI mucosa.
If you give a dog a dose of Pepto-Bismol or Kaopectate and he later passes dark tarry stools, how much should you worry?
not much - this is to be expected.
Is is possible for bismuth subsalicylate administration to interfere with abdominal radiographs? How?
yes - it is radio-opaque - shows up white on radiographs
Should Pepto-Bismol or Kaopectate be given to cats? Why or why not?
no - break down to an aspirin - like compound - salicylate - can be toxic to cats.
What is the purpose of laxatives, cathartics, and purgatives? What are the indications for use of laxatives, cathartics, and purgatives?
to promote defecation and emptying of the GI tract. hairballs, chronic constipation, GI radiographs (empty out the GI tract so intestinal contents do not interfere with radiographic quality), post - surgical in the perianal area (so patients will not refuse to defecate due to pain from firm stool).
What are laxatives, cathartics, and purgatives? How do they work?
compounds that make stool easier to pass. by increasing fluid content, or by making the stool more "slippery"
More specifically, what are laxatives used for?
used to soften the stool.
More specifically, what are purgatives used for?
used to empty the bowels
Concerning laxatives, cathartics, and purgatives, which category is least stressful to the patient? Which is most stressful?
laxatives are least stressful, purgatives are most stressful.
What are the 2 main types of laxatives?
- emollient laxatives
- bulk laxatives
What are the 2 types of emollient laxatives?
- lubricant oils
- stool softeners
What are the 2 main types of cathartics?
- osmotic cathartics
- hypertonic salts
How do irritant laxatives/cathartics work?
by causing increased peristaltic contractions
Is it OK to use an irritant laxative/cathartic in a patient with an intestinal obstruction?
Name 2 main types of irritatn laxatives/cathartics. Are these commonly used in veterinary medicine?
- castor oil, diphenylmethanes
- not commonly used in veterinary medicine
What plant does caster oil come from? Is caster oil itself irritant? What irritant does caster oil change to in the intestines?
- caster bean plant
- castor oil itself is not irritant
- ricinoleic acid is the irritant
What deadly toxin is also extracted from the castor bean plant? Why isn't castor oil deadly?
ricin is the deadly toxin. ricin is water soluble, not oil soluble.
Name 2 diphenylmethane irritatn laxatives/cathartics.
- bisacodyl - Dulcolax
- phenophthalein - Exxlax (being phased out)
How do bulk laxatives work?
by osmotically pulling water into the GI tract. also causes distension of gut wall, stimulating peristalsis.
List 2 indigestible fiber compounds used as bulk laxatives.
Name a commonly used hydrophilic bulk laxative.
psyllium - Metamucil
How do hyperosmotic agents, or hypertonic salts, work?
contain Mg++ or P+ ions that are poorly absorbed, stay in the guy lumen, and draw fluid in by osmosis.
Name 2 hypertonic salt cathartics.
- magnesium - Milk of Magnesia, Epsom salts
- phosphate - Fleet enema
Why should phosphate enemas not be used in cats?
phosphates can be absobed systemically, can cause hypocalcemia, and other electrolyte abnormalities, especially in cats
How do intestinal lubricants work?
they are not absorbed systemically, can cause hypocalcemia, and other electrolyte abnormalities, espeically in cats.
Why should lubricatns not be used every day for a long period of time?
dissolve lipid-soluble vitamins, which are then excreted. Patient can get vitamin deficiencies
Name 4 lubricants.
- mineral oil
- white petrolatum
- cod liver oil
How is mineral oil most commonly used?
given to horses by stomach tube to treat impactions
What is white petrolatum? What type of products commonly contain it?
hydrogenated mineral oil. cat hairball remedies
What are stool softeners used for? How do they work?
used to treat hard, dry feces - difficult for the patient to pass. or used after perianal surgery. they work because they are "surfactants" - "wetting" agents - reduce surface tension of stool, allows water to penetrate. also stimulate colonic secretions.
List 1 stool softener.
docusate sodium - Colace
What 4 types of cells are found in the glands linig the stomach and what substance do they secrete?
- parietal or oxyntic cells - secrete HCl - hydrochloric acid.
- chief cells secrete pepsinogen
- mucous cells secrete mucus
- G cells secrete gastrin
What is "pepsinogen"?
inactive form of pepsin - an enzyme that breaks down protein. pepsinogen is secreted into the stomach lumen, where HCl breaks it down to pepsin - active form of the enzyme
How do parietal cells secrete HCl?
parietal cells cannot make HCl inside themselves - would cause damage. parietal cells secrete H+ and CL- separately into the stomach lumen, where they combine to form HCl.
What 3 types of receptors do parietal cells have to control HCl secretions?
- gastrin receptors
- acetylcholine receptors (parasympathetic)
- histamine receptors
What substances stimulate secretions of hydrochloric acid - HCl - by parietal cells in the stomach?
What are GI ulcers? Where are they located?
specific localized areas in the stomach, duodneum, or esophagus where the GI mucosa has been eaten away to expose deeper tissue - through the mucosa into the submucosa, muscle layer, or even deeper
List some of the causes of ulcers.
- metabolic disease
- gastric hyperacidity
- mast cell tumors
List the clinical signs of ulcers
- hematemesis - fresh red blood
- semi-digested coffee-ground looking blood
List the 4 main categories of anti-ulcer drugs.
- systemic antacids
- local antacids
- gastromucosal protectants
What is the difference between systemic antacids and local antacids?
systemic antacids have to be absorbed into the circulation and attach to receptors on the parietal cells to produce their effect. local antacids combine with and directly neutralize acids in the stomach lumen
List the 2 types of systemic anti-ulcer drugs.
H2 (histamine) blockers, acid pump blockers
How do H2 blockers systemic antacids work?
by blocking H2 histamine receptors on gastric parietal cells, preventing histamine from stimulating HCl production
List 3 H2 blocker drugs, in order from the oldest with the most side effects to the newest with the least side effects.
- cimetidine - Tagamet
- ranitidine - Zantac
- famotidine - Pepcid
How do H2 blocker drugs create their side effects?
by inhibition of liver enzyme systems responsible for metabolizing certain other drugs. may lead to toxic levels of these other drugs if given to the patient at the same time.
How does the acid pump blocker type of systemic antacid work?
binds to the luminal surface of gastric parietal cells, and inhibits their H+ pumps - less H+ released into the lumen of the stomach, less HCl produced.
Name 1 acid pump blocker drug
List 3 categories of local antacids
- calcium - Tums, Rolaids (may cause constipation)
- aluminum - Amphogel (may cause constipation)
- magnesium - Milk of Magnesia, Carmilax (may cause diarrhea)
Why should you not give a patient tetracycline and Tums at the same time?
C++ in Tums binds tetracycline and is ineffective
Why are aluminum and magnesium combined in the local antacid Maalox?
Al tens to cause constipation. Mg tends to cause diarrhea. they balance each other out
What other purpose is Amphogel used for?
since it also binds phosphate in the diet when it is given with food, Amphogel is used to treat hyperphosphatemia in some renal patients.
How does the antiulcer gastromucosal protectant drug sucralfate (Carafate) work?
"ulcer band - aid" - sticks to ulcer site, protects it - binds with proteins in open ulcer. also stimulates release of prostaglandin E which increases secretions and protects
Should sucralfate (Carafate) be given with antacids? Why or why not?
no - need HCl to be present for sucralfate to work
Name the synthetic prostaglandin drug that can be used to help heal ulcers
misoprostol - Cytotec
Name 3 GI stimulant drugs.
- neostigmine - Stiglyn
- metaclopramide - Regaln
- cisapride - Propulsid
What is neostigmine used for?
ruminatoric - stimulate atonic rumen
What does metaclopramide do, and what conditions is it used to treat?
stimulates GI tract motility. used to treat gastroesophageal reflux, delayed gastric emptying, and other GI motility disorders
What does cisapride - Propulsid do? What conditions is it used to treat?
stimualtes GI tract motility. used to treat severe constipation in cats
Is cisapride still available for human use? Is it available for veterinary use?
not available for human use, it is available for veterinary use.
What is the drug poloxalene used for?
to treat or prevent frothy bloat in cattle on legume pastures - reduces surface tension, breaks up small bubble into bigger ones that can be belched out easier
Are antimicrobials routinely indicated in most GI problems?
Why is the antimicrobial drug sulfasalazine sometimes used for GI problems?
breaks down in to a sulfa (sulfapyridine) and 5-aminosalicylic acid, aka mesalamine (an anti-inflammatory related to aspirin) in the gut. it is used to treat certain inflammatory bowel diseases.
What GI problem is sulfadimethoxine used for?
to treat coccidiosis
Why is the antimicrobial drug metronidazole (Flagyl) sometimes used for GI problems?
used to treat giardia, some anaerobic bacterial infections
What type of side effects can occur with extended used of metronidazole?
When are pancreatic enzyme supplements (such as Viokase) used for GI problems?
when patient has exocrine pancreatic insufficiency - does not produce enough enzymes (lipase, amylase, proteases) to digest food normally. add to food, incubate 20 minutes before feeding.
Are corticosteroids commonly indicated or casually given for GI problems?