Therapeutics for GI Diseases- LA

Question 1

describe omeprazole/proton pump inhibitors in horses

Answer 1

1. gastrogard is the only FDA-approved treatment proven to:
   -control gastric pH
   -speed clinical recovery
   -heal squamous gastric ulcers
2. best absorbed if given 30 min before feeding
3. compounded omeprazole is rarely bioavailable and generally ineffective
4. ulcergard used as preventative in horses at risk for gastric ulcers
   -same drug, different doses for treatment versus prevention

Question 2

describe proton pump inhibitors in ruminants and pigs

Answer 2

1. omeprazole has limited to no efficacy in mature ruminants
   -destroyed by gastric acidity of multiple stomachs
2. pantoprazole (IV) is an alternative, but cost prohibitive in cattle
   -can use in small ruminants/camelids and pigs too if willing to pay
   -cattle = limited options
3. esomeprazole (S-enantiomer of omeprazole) in sheep

Question 3

describe sucralfate in horses

Answer 3

1. indicated for symptomatic treatment of gastric ulceration from a variety of causes
2. forms a protective barrier over ulcers, promoting healing
3. in humans is as effective as antacids in healing ulcers, but NOT in horses

Question 4

describe H2 receptor antagonists

Answer 4

1. ranitidine:
   -questionable efficacy in horses
   -not (commonly) used in ruminants, camelids, pigs
2. prostalganding E1 analog/misoprostol (horses)
   -may be helpful for pyloric lesions
   -often combined with sucralfate
   -causes abortion so BIG owner safety issues in relation to who can handle the drug

Question 5

describe treatment of acute colitis

Answer 5

1. the most important treatment is fluid therapy!
   -acute colitis causes dehydration, electrolyte loss, and acidosis
2. severe hypoproteinemia may require plasma or hetastarch
3. endotoxemia management includes NSAIDs (flunixin meglumine), endotoxin antisera, and polymixin
4. cryotherapy (continuous ice) can be used to prevent laminitis
5. oral antidiarrheals may be helpful
   -smectite
   -bismuth subsalicyclate
   -probiotics: S. boulardii has supporting evidence
   -pysllium promotes colonic flora changes beneficial for colonic repair
   -typically NOT recommended to use drugs that induce ileus to control diarrhea in horses

Question 6

describe use of analgesics

Answer 6

for management of equine acute colitis and colic

1. NSAIDs:
   -flunixin meglumine: analgesic, anti-inflammatory, antipyretic
   -pain often alleviated in less than 15 min post-admin
   -repeated dosing can mask pain or delay diagnosis
   -being a nonselective NSAID, can cause right dorsal colitis and renal papillary necrosis when used repeatedly
2. alpha-2 adrenergic agonist
   -xylazine: pain and sedation, short active, transient ileus, bradycardia, hypotension

-detomidine: pain and sedations, more potent and longer acting; bradycardia, hypotension, sedation

3. opioid agonist-antagonist
   -butorphenol: pain and sedation; narcotic, ileus, hyperexcitability if used without an alpha-2 adrenergic agonist

Question 7

describe treatment of hepatic insufficiency in horses

Answer 7

1. glucose therapy: CRI IV
2. hypertonic saline may be used for cerebral edema
3. reducing ammonia and enteric toxins
   -lactulose to reduce ammonia production and trap ammonium
   -neomycin to decrease colonic bacterial load (can cause diarrhea, rarely used)
4. nutritional management:
   -diet should be high in carbohydrates and low in proteins
   -protein sources should be rich in branched-chain amino acids
   -avoid alfalfa and legumes due to high protein content
5. additional considerations:
   -pentoxifylline or steroids may slow or prevent hepatic fibrosis
   -SAMe (antioxidant)

*avoid diazepam and be cautious with bicarbonate supplementation (can exacerbate hepatic encephalopathy)

Question 8

describe prokinetics

Answer 8

used for delayed gastric emptying, ileus (horses)

1. lidocaine: suppresses sympathetic inhibition of GI motility, increasing gut contractions
2. metaclopramide:
   -enhances GI motility by blocking D2 receptors to reduce inhibition of GI motility and stimulating 5HT4 receptors to increases Ach release
   -restlessness with higher doses or rapid admin though
3. cisapride, neostigmine

Question 9

describe laxatives

Answer 9

used for impaction in horses

1. mineral oil: lubricant
   -for colonic or small colon impactions
2. psyllium mucilloid: soluble fiber, bulk forming
   -for colonic or cecal impactions, sand impactions
   -give via NGT
3. magnesium sulfate: epsom salts, osmotic laxative
   -for colonic or cecal impactions (NOT small colon, is irritating)

Question 10

describe parasiticides

Answer 10

1. fenbendazole:
   -benzimidazole antiparasitic
   -selectively binds to beta-tubulin, a protein subunit of microtubules in parasite cells
   -for nematodes and cestodes
   -for liver flukes/trematodes: albendazole
2. ivermectin:
   -macrocyclic lactone antiparasitic
   -binds glutamate-gated chloride channels, paralyzing parasites
   -for nematodes, including strongylus, parascaris equorum, haemonchus, ostertagia, and cooperia
   -increasing resistance = sadness
3. praziquantel:
   -isoquinolone antiparasitic
   -increases parasite membrane permeability to calcium, causing paralysis and expulsion
   -for tapeworm/cestode infections: anoplocephala, taenia
   -also drug resistance

any drug that is very lipophilic will end up excreted some in feces and persist in the environment for a while = increase resistance