Week 6: Drugs Acting on the Gastrointestinal Tract

Movement

Peristalsis and Segmentation. It shows how peristaltic contractions (A) move food through the tract while segmentation (B) aids in breaking down and mixing food for efficient digestion.

GIT

Gastrointestinal Disorders

One of the most common complaints

Infectious diseases, dietary excess, adverse drug effects, systemic diseases

ANTISIALOGOGUES

• decrease salivary flow

• important especially during anesthesia

• anticholinergics

• side effects: dry mouth, constipation, CNS stimulations, tachycardia, pupillary dilation

ANTISIALOGOGUES

EXAMPLES:

Glycopyrrolate

Atropine

ANTIDIARRHEALS

Diarrhea

• sign of underlying disease

• increased frequency and/or liquidity of feces

• acid- base imbalance, reduced nutrient uptake

ANTIDIARRHEALS

A. Anticholinergics
B. Protectans/Adsorbents

C.Narcotic Analgesics
D. Probiotics
E. Metronidazole

ANTIDIARRHEALS

A. Anticholinergics

ANTIDIARRHEALS

A. Anticholinergics

can treat tenesmus

blocks Ach release

ANTIDIARRHEALS

A. Anticholinergics

i. atropine
ii. propantheline
iii. aminopentamide
iv. methoscopolamine
v. N-butylscopolammonium

ANTIDIARRHEALS

A. Anticholinergics

can treat tenesmus

blocks Ach release

i. atropine
ii. propantheline
iii. aminopentamide
iv. methoscopolamine
v. N-butylscopolammonium

ANTIDIARRHEALS

B. Protectans/Adsorbents

ANTIDIARRHEALS

B. Protectans/Adsorbents

• coats inflamed intestinal mucosa (protectants)

• binds bacteria and/or digestive enzymes and/or toxins (adsorbents)

ANTIDIARRHEALS

B. Protectans/Adsorbents

i. bismuth subsalicylate

ii. kaolin/pectin

iii. activated charcoal

ANTIDIARRHEALS

B. Protectans/Adsorbents

i. bismuth subsalicylate

ANTIDIARRHEALS

B. Protectans/Adsorbents: i. bismuth subsalicylate

• coats intestinal mucosa

• antiendotoxic

• weak antibacterial

• subsalicylate = anti- inflammatory

• darken stool

• causes opacities in xrays

ANTIDIARRHEALS

B. Protectans/Adsorbents

ii. kaolin/pectin

ANTIDIARRHEALS

B. Protectans/Adsorbents: ii. kaolin/pectin

• has adsorbent and protective properties

• adsorbs bacteria and toxins in the gut

• protects inflamed intestinal mucosa

ANTIDIARRHEALS

B. Protectans/Adsorbents

iii. activated charcoal

ANTIDIARRHEALS

B. Protectans/Adsorbents: iii. activated charcoal

• fine, black, tasteless powder

• for ingestion of certain toxins

• may be useful for adsorption of endotoxins

  • “universal antidote”

ANTIDIARRHEALS: B. Protectans/Adsorbents: iii. activated charcoal

• “universal antidote”

ANTIDIARRHEALS

C. Narcotic Analgesics

ANTIDIARRHEALS: C. Narcotic Analgesics

• decrease secretions and flow of feces

• increases segmental contractions

• CNS depression/excitement, ileus, urinary retention, bloat, and constipation

ANTIDIARRHEALS: C. Narcotic Analgesics

i. diphenoxylate

ii.loperamide

iii.paregoric

ANTIDIARRHEALS

D. Probiotics

ANTIDIARRHEALS: D. Probiotics

• seeds the GI tract with beneficial bacteria

• Lactobacillus spp., Enterococcus faecium, Bifidobacterium spp.

• competes with pathogenic bacteria

• may be refrigerated to maintain viability

• plain yogurt may be used

ANTIDIARRHEALS

E. Metronidazole

ANTIDIARRHEALS: E. Metronidazole

antibiotic effective vs anaerobic bacteria

sometimes used as antidiarrheal

STOOL LOOSENERS

Constipation

Condition wherein passage of feces is slow or absent

STOOL LOOSENERS

A. Laxatives

B. Cathartic

C. Purgatives

STOOL LOOSENERS

i. osmotic
ii. stimulant
iii. bulk-forming

iv. emollients

STOOL LOOSENERS

i. osmotic

STOOL LOOSENERS: i. osmotic

• pulls water into colon
• saline or sugar based product

STOOL LOOSENERS: i. osmotic

A. Lactulose
B. Na phosphate with sodium biphosphate

C. Magnesium sulfate
D. Magnesium hydroxide
E. Polyethylene Glycol Electrolyte Solution

STOOL LOOSENERS

ii. stimulant

STOOL LOOSENERS: ii. stimulant

• increases peristalsis
• maybe absorbed systemically

STOOL LOOSENERS: ii. stimulant

A. bisacodyl (Dulcolax)

• • must not be crushed or chewed
  • avoid milk/antacid administration

B. castor oil
• ricinocleic acid
• inihibits water and electrolyte absorption

STOOL LOOSENERS: i. stimulant: A. bisacodyl (Dulcolax)

• 
  

• • must not be crushed or chewed
  • avoid milk/antacid administration

STOOL LOOSENERS i. stimulant: B. castor oil

• ricinocleic acid
• inihibits water and electrolyte absorption

STOOL LOOSENERS

iii. bulk-forming

STOOL LOOSENERS: iii. bulk-forming

• natural fibrous substances or semisynthetic compounds
• most contain psyllium and plantago seeds
• minimal effect on nutrition absorption

• not systemically absorbed

STOOL LOOSENERS: iii. bulk-forming

A. psyllium hydrophilic mucilloid

B. polycarbophil
C. bran

STOOL LOOSENERS:

iv. Emollients

STOOL LOOSENERS: iv. Emollients

• reduce stool surface tension
• reduce water absorption
• facilitates passage of fecal material
• fecal wetting agents that allows easier penetration and mixing of fats

STOOL LOOSENERS: iv. Emollients

A. docusate sodium
B. docusate calcium

C. docusate potassium

D. petroleum products

ANTIEMETICS

ANTIEMETICS

ANTIEMETICS

1. Phenothiazines

2. Antihistamines

3. Anticholinergics

4. Procainamide Derivatives

5. Serotonin Receptor Agonist

6. Neurokinin Receptor Antagonist

ANTIEMETICS

1. Phenothiazines

ANTIEMETICS: 1. Phenothiazines

• inhibits dopamine in CRTZ
• side effect: hypotension and sedation
• lowers seizure threshold
• CI: vomiting pxs with abnormal GI motility

ANTIEMETICS: 1. Phenothiazines

• inhibits dopamine in CRTZ

ANTIEMETICS: 1. Phenothiazines

• side effect: hypotension and sedation

ANTIEMETICS: 1. Phenothiazines

• lowers seizure threshold

ANTIEMETICS: 1. Phenothiazines

• CI: vomiting pxs with abnormal GI motility

ANTIEMETICS: 1. Phenothiazines

A. acepromazine

B. chlorpromazine

C. prochlorprezine

D. perphenazine

ANTIEMETICS

2. Antihistamines

ANTIEMETICS: 2. Antihistamines

• controls vomiting in small animals
• motion sickness, vaccination rxs, inner ear problem
• may cause sedation

ANTIEMETICS: 2. Antihistamines

A. diphenhydramine
B. meclizine

ANTIEMETICS:

3. Anticholinergics

ANTIEMETICS: 3. Anticholinergics

blocks Ach peripherally
for motion sickness
side effects: dry mouth, constipation, urinary retention, tachycardia
CI: pxs with glaucoma, pyloric obstruction

ANTIEMETICS: 3. Anticholinergics

CI: pxs with glaucoma, pyloric obstruction

ANTIEMETICS: 3. Anticholinergics

A. aminopentamide

B. atropine
C. propantheline

ANTIEMETICS:

4. Procainamide Derivatives

ANTIEMETICS: 4. Procainamide Derivatives

centrally and peripherally blocks CRTZ

CI: pxs with GI obstructions, perforations, and/or hemorrhage

ANTIEMETICS: 4. Procainamide Derivatives

example: metoclopramide

• for vomiting assoc w/ chemotherapy

• stimulates upper GI motility

ANTIEMETICS:

5. Serotonin Receptor Agonist

ANTIEMETICS: 5. Serotonin Receptor Agonist

reduces serotonin uptake

A. ondansetron
B. dolasetron
C. granisetron

ANTIEMETICS

6. Neurokinin Receptor Antagonist

ANTIEMETICS: 6. Neurokinin Receptor Antagonist

antagonizes NK receptors in the vomiting center
example: maropitant citrate

ANTIEMETICS: 6. Neurokinin Receptor Antagonist

example: maropitant citrate

EMETICS

induces vomiting esp in poisoning and drug overdoses
CI: ingestion of caustic substances

EMETICS

A. Centrally Acting
B. Peripherally Acting

EMETICS: A. Centrally Acting

apomorphine

• morphine derivative

• emetic drug of choice for dogs

EMETICS: A. Centrally Acting: Apomorphine

• morphine derivative

• emetic drug of choice for dogs

EMETICS: A. Centrally Acting

xylazine

• emetic drug of choice for cats

EMETICS: A. Centrally Acting: Xylazine

emetic drug of choice for cats

EMETICS: B. Peripherally Acting

ipecac syrup

• orally administered

• irritation of mucosa

• evacuates contents of stomach and intestines

EMETICS: B. Peripherally Acting: Ipecac syruo

• orally administered

• irritation of mucosa

• evacuates contents of stomach and intestines

ANTI-ULCERS

Ulcers

• erosions in the gastric mucosa

• may be due to stress, drug induced, metabolic diseases

ANTI-ULCERS

A. Antacids
B. H2 Receptor Blocker
C. Mucosal Protective Drugs

D. Proton Pump Inhibitors

ANTI-ULCERS

A. Antacids

ANTI-ULCERS: A. Antacids

• neutralizes HCl and reduces pepsin activity

• interacts with other drugs by adsorption

i. systemically acting

ii. locally acting

ANTI-ULCERS: A. Antacids (Systemic)

• absorbed in the blood stream

Examples:

• NaHCO3

• Ca(CHO3)2

ANTI-ULCERS: A. Antacids (Systemic)

• NaHCO3

• Ca(CHO3)2

ANTI-ULCERS: A. Antacids (Non- Systemic)

• stays within the GIT

components

• Magnesium OH

• Aluminum OH

• Aluminum + Magnesium

ANTI-ULCERS: A. Antacids (Non- Systemic)

• Magnesium OH

• Aluminum OH

• Aluminum + Magnesium

ANTI-ULCERS

B. H2 Receptor Antagonist

ANTI-ULCERS: B. H2 Receptor Antagonist

blocks H2 receptor of parietal cells

examples:

• cimetidine

• ranitidine

• famotidine

• nizatidine

ANTI-ULCERS: B. H2 Receptor Antagonist

• cimetidine

• ranitidine

• famotidine

• nizatidine

ANTI-ULCERS

C. Mucosal Protective Drugs

ANTI-ULCERS: C. Mucosal Protective Drugs

• pepsin inhibitors

• example

  • sucralfate

• covers the ulcer and protects it from stomach acids

• gastroduodenal protectant

ANTI-ULCERS: C. Mucosal Protective Drugs

• sucralfate

ANTI-ULCERS

D. Proton Pump Inhibitors (PPIs)

ANTI-ULCERS: D. Proton Pump Inhibitors (PPIs)

irreversibly binds H-K-ATPase on the surface of parietal cells

examples

omeprazole

lansoprazole

ANTI-ULCERS: D. Proton Pump Inhibitors (PPIs)

omeprazole

lansoprazole

ANTI-FOAMING AGENTS

reduce or inhibits foam formation foam

formation due to excess legume ingestion

examples:

• poloxalene

• polymerized methyl silicone

ANTI-FOAMING AGENTS

poloxalene
polymerized methyl silicone

ENZYME SUPPLEMENTING

for treatment of pancreatic exocrine insufficiency (PEI)

contains pancrealipase:

amylase

lipase

protease

ENZYME SUPPLEMENTING

contains pancrealipase:

amylase

lipase

protease

MOTILITY ENHANCING DRUGS

stimulates movement of ingesta throughout the GUT