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Pharmacology > Unit 7 - GI Drugs > Flashcards

Unit 7 - GI Drugs Flashcards

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1
Q

What are the clinical signs of gastrointestinal injury/dz?

A

V/D, constipiation, colid, bloat
all are physiological functions intended to protect animal from harmful substances that may have been ingested
definitions related to the area of injury or dz

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2
Q

What is GI movement controlled by?

A

nervous system - parasympathetic which stimulates receptors w/ acetylcholine (vagus nerve carries nerve impulse to and from abdominal organs)
Hormones
endocrine system

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3
Q

What happens to the GIT when given a parasympathetic?

A

stims receptors w/ acetylcholine
vagus nerve carries nerve impule to and from abdominal organs
drugs that mimic acetylcholine - inc digestive secretions, gut smooth muscle tone and mobility
improve blood flow

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4
Q

What happens to the GIT when given a sympathetic?

A

stimulates receptors w/ norepinephrine, stims adrenal glands to release epinephrine
dec blood flow to GIT, gastric and enteric motility, digestive secretions
Therefore - dec digestion and absorption of nutrients

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5
Q

What is the emetic center

A

Vomiting center
a group of special neurons loc in medullary portion of brain
sends and receives neurons to stimulate the vomiting reaction
Coordinates smooth muscle contractions and the act of vomiting itself - horses, rabbits, rats and guinea pigs cannot vomit

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6
Q

What are the major receptors associated w/ emetic or antiemetic drugs?

A

serotonin, acetylcholine, histamine, dopamine, norepinephrine/epinephrine

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7
Q

What are the 5 mechanisms to stimulating vomiting?

A
  1. binds to receptors w/ emetic center and stims neurons
  2. Binds to receptors on chemoreceptor trigger zone which send signal to emetic center
  3. local nerve signals from distended or irritated region such as pharynx, stomach, duodenum
  4. Signals from overactive inner ear balance mechanism
  5. Emotional center in brain - due to trauma or emotional upset
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8
Q

What is the chemoreceptor trigger zone?

A

monitors blood and CSF for chemicals that can stimulate vomiting
has all major receptors found in emetic center and also receptors for opioids
the number and types of receptors varies w/ species and individuals

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9
Q

What receptors are increased in cats? Why does this cause? Which species has less alpha receptors?

A

cats have inc population of A-rceptors on emetic center so epinephrine and norepinephrine stim or drugs that stimulate these receptors will inc likelihood of vomiting
Dogs have less A receptors

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10
Q

Between dogs and cats, which has more dopamine receptors?

A

dogs

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11
Q

What are the two method of actions for emetics?

A
  1. central acting emetics turn on the CRTZ and/or vomit center loc in the brain. Body senses presence of a “toxin” and triggers vomit to protect itself
  2. peripheral acting emetics irritate/activate nerves in the stomach
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12
Q

Where might emetics be indicated for?

A

toxin ingestion
must be given within 4 hours of ingestion
removes 40-60% of gastric contents w/ each vomit
works best if small amount of food given prior
Many toxins already cause vomit: do not need to give an additional emetic
ask owner for hx

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13
Q

what situations do we never give emetics?

A

NEVER induce vomit if caustic, acid or alkaline (can burn esophagus or lungs)
induce vomit if FB, if unconscious or siezuring
never induce in horses, ruminants, birds, rabbits bc they cant vomit
Never induce if bloat, gastric torsion or esophageal damage
ALWAYS check MSDS or poison control before inducing vomit

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14
Q

In what situations do we induce vomit?

A

toxins!!
rodenticides, anti-freeze, chocolate, plant toxicitities (lillies, foxglove)
most medication overdoses, including NSAIDs, anti-parasites, coccidiostats
Vomit within 4hrs of ingestion is most effective; otherwise
some toxins (chocolate) may cause vomit at a certain dose
ALL toxins have a species-specific toxic dose

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15
Q

How can mu-acting opiods induce vomit?

A

turns on CRTZ and vomit center of the brain
only works on first dose - need high enough first dose, otherwise sedation occurs and turns down vomit center
Some animals will not respond
can reverse with naloxone after vomited
most commonly used - apomorphine, hydromorphone

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16
Q

What is apomorphine used for?

A

1st choice in dogs
conjuctival tablet form
can dissolve in sterile saline and squirt into conjunctiva (rec flush as irritating) OR filtered via micro-filter (to sterilize) and then give IV
1st dose only
not in cats - lack receptors in the CRTZ

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17
Q

What is hydromorphone used for?

A

1st dose only in SA (best in dogs)
IM works best. SQ works. IV does NOT induce vomit bc sedation hits too fast - now aspiration risk
more sedation than apomorphine

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18
Q

What is xylazine used for?

A

A2 AGONIST
1st choice in cats
prods emesis in 90% of cats only 30% in dogs which have less a2 receptors in CRTZ

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19
Q

What is hydrogen peroxide (3%) used for?

A

direct irritant
damages mucosal lining of the stomach
there is a per kg dose AND a max dose of 3 tbsp (45mls) for ANY sized animal. Can exceed max dose
give 1 dose, wait 15min. can repeat once
will cause serious s/e if gets into lungs (corrosion, hemorrhage, necrosis)
can cause gastric perforation if give too much; risk still exists if given at recommended dose; increased risk if pre-existing erosion/ulcer and in certain patients

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20
Q

What is warm salt solution used for?

A

local emetic
must give water or IV fluids to reduce risk of salt toxicity or dehydration

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21
Q

What ways do antiemetics work?

A

can block CRTZ, vomit center
can control nausea
can dampen peripheral nerves in GI tract
Give 1st dose parenterally so will be absorbed
give when natural vomiting reflex in excessive and not considered helpful ex. pancreatitis

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22
Q

How do phenothiazine tranquilizers work? WHat is a common one?

A

acepromazine
works by blocking several types of receptors in CRTZ and vomiting center
s/e - Dec BP, small degree of sedation at antiemetic dose - often used for motion sickness

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23
Q

What are prokinetic drugs?

Study These Flashcards
A

metoclopramide (reglan)
blocks several receptors centrally/locally
In upper GI motility, muscle tone of lower esophagus, gastric motility in normal direction w/o inc secretions
relaxes pyloric outflow
All improve GIT flow in aboral direction

24
Q

When are prokinetic drugs used vs not used?

Study These Flashcards
A

used for intermittent vomiting of bile and mucus in otherwise healthy dogs
Dont use in animals prone to seizures
anticholinergic drugs contraindicated as they reduce gut motility

25
What is a serotonin antagonist used for?
newer classes of antiemetics - ondansetron binds to serotonin receptors in CRTZ and inhibits release of serotonin used in dogs and cats w/ refractory vomit that doesn't respond to other drugs parvo in dogs pancreatitis in cats
26
What is maropitant?
cerenia blocks neurokinin 1 receptors (NK1) in the vomit center used to prevent motion sickness and vomiting start w/ injectable (SQ), then switch to oral form
27
What are anti-diarrheals?
drugs that decrease feces
28
How do anti-diarrheals work?
1. affect motility - slow down peristalsis so there is inc absorption of water from feces; feces become firmer 2. blocks secretions 3. absorbents and protectants stay in GI tract - sooth GIT; firm stool, binds to toxins and irritants causing the diarrhea 4. antibiotics, pre/probiotics treat abnormal GI flora and restore normal flora
29
What are motility modifiers?
opioids/opioid-related agents mu-receptor agonist dec peristalsis, inc segmental contractions so overall effect is inc absorption of fluid from colon S/E: sedation/excitement, ileus to constipation Ex. imodium is a human OTC: diphenoxylate (lomotil) caution w/ breeds with MDR1 mutation use with caution if cause of diarrhea unknown
30
What does blocking secretions do as an anti-diarrheals?
anything that inc effect of ACH or the activity of parasymp NS can inc GIT secretions like organophosphates irritation/stim of cells lining GIT = sections of ions that osmotically pull water into lumen of gut ex. bacterial endotoxins inflam of these cells cause damage to point of blood to escape into lumen = blood diarrhea potential for dehydration
31
What are some drugs that block secretions of the GIT?
salicylates = anti inflam action or pepto-bismol Sulfasalazine - contains a sulfonamide antibiotic component - s/e keratoconjunctivitis sicca
32
How do adsorbents and protectants work?
stays in GI tract; not absorbed coats intestinal mucosa - soothes inflamed gut, forms a barrier effect adsorbents also bind to irritants, toxins some can promote fibrosis/healing some will solidify diarrhea may not address underlying issue few adverse effects - takes 1-2hrs after other oral drugs or may impair their absorptiont
33
What is bismut subsalicylate?
peptobismol otc/eldu contains 2 drugs - 1. subsalicylate (aspirin derivative) anti inflam. 2. bismuth coats the intestines for protectant caution or avoid in cats (aspirin based toxicity), may blacken stool (masks melena)
34
How is barium used as an anti-diarrheal?
radiocontract agent, outlines GIT lines, soothes, absorbs, firms stool always alert ASAP if accidentally delivered into airways when giving by stomach tube; may need emerg tx as causes lung damage
35
How is activated charcoal used as an anti-diarrheal?
fine black porous powder that absorbs toxins stays in GIT; acts as a sink and draws toxins from circulation effective if given <4hours of ingesting toxin if toxin undergoes entero-hepatic recirculation, can give even if more than 4 hours have elapsed from ingestion liquid can be syringed or stomach tubed into mouth; mix well before use (settles) warn owners may have vomit or black diarrhea initially; will stain
36
What are some drugs that affect intestinal flora?
metronidazole - most common antibiotic for diarrhea in SA, very effective against anaerobes (clostridia) and giardia. S/E: V/D, neurological symptoms Tylosin - most common in cattle/swine, not horses Prebiotics - given to promote growth and survival of beneficial bacteria in the gut. Ex. Vit B12, folate, iron, specific sugars probiotic - live, beneficial bacteria, not a drug, anaerobic (use ASAP after exposing to air) ex. prostora, yoghurt w/ live cultures
37
What are laxatives, cathartics and purgatives?
drugs that increase feces w/ increasing degrees of aggressiveness
38
What do laxatives, cathartics and purgatives work by?
work by inc fluid content of stool or irritating gut to inc peristalsis inc BMs used for constipation, hairballs, to empty GIT b4 GI sx
39
What are irritant laxatives?
chemical irritant; stimulates nerve endings in intestines to inc peristalsis may have systemic s/e ex. castor oil, bisacodyl different classes: laxatives - mild purgatives - stronger cathartics - strongest (cramping, straining
40
rank laxatives, purgatives and cathartics from mild, stronger and strongest
laxatives - mild purgatives - stronger cathartics - strongest (cramping, straining
41
What are osmotic laxatives?
pull water into colon (into feces so softer and easier to move) s/e: dehydration, constipation, dependence (cannot stop abruptly); salt-based laxatives may disturb electrolytes lactulose - sugar that is not absorbed by the intestines: draws water milk of magnesia, epsom salts
42
What are bulk-forming laxatives?
insoluble fibre incorporates into feces; inc fecal bulk so looks normal and absorbed water Ex. psyllium (Metamucil), bran, pumpkin - used to prevent and treat sand colic in horses
43
What are emollient laxatives?
detergent-like chemicals reduce stool surface tension so water is absorbed into fecal matter few side effects ex. docusate sodium succinate
44
What do osmotics, bulkforming ane emollients all work by?
increasing water content in feces
45
What are lubricants?
coats GI tract and feces and helps to slide things along; passes faster w/ less effort ex. mineral oil (stomach tube only, do NOT get into lungs) white petroleum or cod liver oil (hairball formulas for cats), glycerine
46
What are antacids?
buffers and alkalinizing agent in the stomach and chemically neutralize pH of the gastric juice - TUMS, rolaids S/e: 1. will alter ionization of other oral drugs work; give 1-2hrs apart 2. chronic use causes gastric acid rebound syndrome; body responds by inc acid prod. avoid chronic use 3. alter absorption of tetracyclines
47
How are histamine 2 receptor antagonists used as anti-ulcer drugs?
ina normal body, histamine binds to H2 receptors and stimulates HCl production anti-histamines bind to and block H2-receptors Ex. ranitidine (zantac), famotidine (pepcid)
48
What are proton pump inhibitors?
anti-ulcer drug most effective and fewest s/e, $$ drug binds to H+ pumps; blocks H+ ions from getting into stomach lumen good for chronic use often co-prescribed fro chronic steroid or NSAID therapy to decrease GI s/e ex. omeprazole or gastrogard
49
What are sucralfate?
sulcrate - mucosal protectant, 3 mechanisms 1. intestinal band-aid: binds to existing ulcers and forms barrier 2. provides a scaffold for fibrocytes to adhere; hastens healing time of ulcers 3. stims prostaglandin prod > inc secretions of protective mucus may interfere w/ drug absorption; give 1-2hrs after, can use chronically
50
When might we use appetite stimulants?
in cats chronic renal dz, pancreatitis, FURD; ANY cause of stress or illness can cause a cat to stop eating bandaid: does not address underlying problem
51
What is cyproheptadine
periactin human antidepressant; works in cats s/e aggression and excitement
52
What does diazepam do in the GIT?
appetite stimulant for cats up to 4 doses max in cats; otherwise will inc risk of acute hepatotoxicity, can give IV or PO
53
What are riminatorics? What do they treat?
Stimulate rumen motility by activating the PNS (indirect-acting cholinergics) ex. neostigmine
54
What are antifoaming drugs? What do they treat
tx's frothy bloat ex. dioctyl sodium succinate (DSS), (antigas) dec surface tension on foam bubbles and cause them to break down. smler bubbles can be passed thru a stomach tube; gas can be belched large volume administered by stomach tube directly into rumen. DO NOT GET INTO LUNGS
55
What are ionophores, what do they treat?
group of antimicrobial drugs to treat coccidia in poultry and cattle used in beef/dairy cattle to balance rumen population of microorganisms to improve conversion of cattle feed into weight and to prevent bloat
56
What species is ionophores toxic to?
horses - do NOT add to horse feed

Pharmacology (12 decks)

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