GIT part 2

Diarrhea

Passage of liquid or loose stools usually at an increased frequency

Possible cause of diarrhea

• Bacteria

• Virus

• Parasite 

• Dietary indiscretion

• Systemic non-gastrointestinal disease

Hypersecretion

• fluid is lost into the intestinal lumen due to bacterial endotoxins  (E. coli, C. jejuni, C. perfringens)

Malabsorption

damage to small intestinal mucosa by infection with rotavirus, coronavirus or cryptosporidia

inflammation

increased permeability/exudation of mucus, blood and protein into the bowel lumen

Altered intestinal motility

decreased contact between luminal content and mucosal surface in the GIT

uncontrolled diarrhea leads to

fluid and electrolyte losses

therapy for diarrhea

• Fluid & electrolyte replacement (to be discussed under Fluid Therapy)

• Maintenance of acid-base balance

• Treatment of specific cause (if possible)

• Relief of abdominal pain

• Dietary management 

• Antidiarrheal

Antidiarrheals

1. Narcotic analgesics

2. Anticholinergics (antispasmodics, motility modifiers)

3. Adsorbents/Protectants

Narcotic analgesics (opiates)

MOA

• Increase segmental contractions

  • Enhance intestinal absorption

• Decrease intestinal secretions 

Clinical use

• Control of diarrhea

examples of opiates

Diphenoxylate

Loperamide

Opiates

drug of choice for canine diarrhea

Anticholinergic drugs (antispasmodics)

MOA

• Decrease intestinal motility & peristalsis; also reduce gastric secretions

Therapeutic use

• Relief of pain & tenesmus associated with large bowel inflammatory disease

• Relief of spasm in gut spasms

• Stress-induced colitis (with cholinergic involvement)

examples of anticholinergic drugs

• Aminopentamide

• Hyoscine

• Propantheline

• Clidinium

• N-butylscopolammonium bromide (Buscopan®)

  • For the treatment of colic in horses; CI in horses with impaction or ileus

protectants/adsorbents

• Protectant action: Coating the intestines thus preventing further irritation/erosion

• Adsorbent action: Bind bacteria and/or toxins thus protecting the GIT mucosa from damage

Kaolin/pectin (protectants)

• Clinical studies have not demonstrated any beneficial effect of its absorption

• May adsorb or bind other administered drugs

Bismuth subsalicylate

• Subsalicylate component has an anti-inflammatory effect & inhibit PG production

• Bismuth coats the GIT mucosa

Activated charcoal: 

• An adsorbent that is used to treat poisoning

Laxatives

• Drugs that loosen and cause the evacuation of bowel contents

• Cathartics/purgatives  – laxatives with a strong/intense effect

indications of laxatives

• Relief of constipation or intestinal impaction

• Removal of toxic materials from the GIT

• To soften stool during rectal, vaginal or uterine prolapse

• To prevent straining during post-surgical care

• To remove gut edema fluid

• To cleanse the bowel before x-ray or endoscopy

Categories of laxatives

1. Osmotic agents

2. Irritants/Stimulants

3. Bulk-forming

4. Lubricants 

5. Stool softeners

Osmotic agents

• Salts or saline products that make the intestinal fluid hyperosmotic but are poorly absorbed in the GIT

• Increased H₂O softens the stool and stimulate stretch receptors to enhance peristalsis

examples of osmotic agents

• MgOH (Milk of Magnesia) 

• Lactulose

stimulant laxatives

MOA

• Irritates the mucosal lining of GIT thus promoting increased peristalsis

Seldom used in veterinary practice

examples of stimulant laxatives

emodin

castor oil

bisacodyl

Bulk-forming laxatives

facilitates defecation by increasing the bulk & fluidity of intestinal content

usually made of indigestible plant materials

absorb water and swell to increase the bulk of intestinal contents, thus stimulating peristalsis

examples of bulkforming laxatives

• Psyllium

• Bran

• Methylcellulose

• Metamucil

Lubricants (emollients)

• Oils and other hydrocarbon derivatives (petrolatum) that soften stool for easier passage through the GIT

• For constipation and fecal impaction

examples of lubricants

mineral oil

petrolatum

stool softeners

• Softens the stool by reducing surface tension and allowing water to penetrate GI contents

• Indications: hard, dry feces (small animals), impaction (horses), digestive upset (cattle)

examples of stool softeners

• Docusate Na (dioctyl sodium sulfoccinate) 

• Docusate Ca (dioctyl calcium sulfoccinate)

Prokinetics

• Increase the movement of ingested material through the GIT; induce coordinated motility patterns in the GIT

• Examples

  • Dopaminergic antagonists

  • Serotonergic antagonists

Dopaminergic antagonists

Metoclopramide

• gastroesophageal reflux

• delayed gastric emptying

• GIT motility disorders in dogs and cats

• GIT stimulation in foals

Domperidone – regulate GIT motility

Serotonergic antagonist

Cisapride

• Enhance ACh release from the nerve endings of the myenteric plexus

• Indication: gastroesophageal reflux, GIT stasis in horse, dogs and cats

Carminatives/antifoaming agents

• Indication: frothy bloat in ruminants

• MOA: act as surfactants (reduce surface tension) thus causing bubbles to break down 🡪 gas is expelled via eructation

antibiotics

• Indications: bloody diarrhea, signs of sepsis

• Note: antibiotics could destroy the normal intestinal microflora and allow the growth of bacterial pathogens

• Examples:

  • Metronidazole – has antibacterial and antiprotozoal effects

  • Amoxicillin, Clavamox, Tylosin 

probiotics

Repopulate the GIT with beneficial bacteria (e.g. Lactobacillus sp., Enterococcus sp., Bifidobacterium sp.) to support intestinal and overall health

Digestive enzymes

• Indication: exocrine pancreatic insufficiency EPI)

• Adverse side effects: diarrhea, nausea, cramping

• Example:

Pancrelipase – contains pancreatic enzymes that facilitate fat, protein and carbohydrate digestion

Appetite stimulants

• Cyproheptadine – antihistamine used as an appetite stimulant in cats

• Mirtazapine – used in dogs and cats

• Diazepam – produce a transient appetite stimulation IV

• Oxazepam

Drugs for treating inflammatory bowel disease (IBD)

IBD

• Characterized by increased numbers of lymphocytes, macrophages, eosinophils and plasma cells in the intestinal wall