GI drugs 2 pt 2

Question 1

categories of drugs used as laxatives and cathartics

Answer 1

1. Emollient Laxatives (lubricants)
   - mineral oil
   - white petrolatum
2. Simple Bulk Laxatives
   - methylcellulose
   - psyllium seed
3. Stool Softeners (Surfactants)
   - Docusate sodium
4. Hyperosmotic Cathartics (salts, sugars)
5. Irritant (Stimulant) Laxatives
   - Castor oil
   - Anthraquinone

Question 2

how do emmollient laxatives work? what are common examples

Answer 2

Lubricating and fecal softening properties
- mineral oil
- white petrolatum

Question 3

mineral oil use, pros and cons?

Answer 3

Emollient Laxatives (lubricants)

• commonly used as a lubricant
• generally bland and safe
  > aspiration pneumonia possible
  > chronic use may actually yield constipation or inhibit absorption of fat-soluble vitamins
• anal leakage in small animals may cause a nuisance for clients

Question 4

white petrolatum use? often combined with what?

Answer 4

Emollient Laxatives (lubricants)

(soft paraffin)
- also classified as a laxative
- oral relief/prevention of hair balls and as a laxative in small animals
- usually product combined with mineral oil and flavouring agents

Question 5

how do simple bulk laxatives work? what are some examples? what species are they used in?

Answer 5

• methylcellulose (Citrucel®); psyllium seed (Metamucil®)
• Hydrophilic in nature and indigestible
• Absorb water causing swelling followed by bowel distension and peristalsis
• Feces remain soft and hydrated
• May require a couple of days to work
• Used in cats, dogs, horses

Question 6

example of commonly used stool softener

Answer 6

Docusate sodium (Anti-Bloat®)

Question 7

how do stool softeners (surfactants) work? primary uses?

Answer 7

• an oral anionic surfactant to decrease surface tension
• allows water to accumulate in feces
• used primarily as an anti-bloat remedy in ruminants
• also used for laxative properties in constipation in all species

Question 8

Hyperosmotic Cathartics (salts, sugars); how do they work, what is their use? how are they administered? what do animals given this also need?

Answer 8

• poorly absorbed by the GI tract, or not at all
• retain or attract water into the lumen by osmotic forces; mucosal secretion
  also possible
  > fecal mass is softened and peristalsis ensues from bowel distension
• generally administered by stomach tube
• used to prepare animal for endoscopy or purging ingested toxins
• drinking water should be available !!
  > contraindicated in dehydrated animals

Question 9

salts used as hyperosmotic cathartics

Answer 9

• Magnesium sulfate (Epsom salts)
• Sodium sulfate (Glauber’s salt)

Question 10

sugars used as hyperosmotic cathartics?

Answer 10

• Mannitol and sorbitol
• Lactulose (Cephulac®)
  > synthetic disaccharide

Question 11

what is lactulose and when is it used?

Answer 11

• synthetic disaccharide
• used as hyperosmotic cathertic for dogs, cats, some birds
• also used in hepatic encephalopathy

Question 12

Irritant (Stimulant) Laxatives; how do they work? how quickly?what can occur with overdose?

Answer 12

• Mechanism of action poorly understood
• Promote fluid and electrolyte accumulation resulting in cathartic effects
• Effects occur quickly ie within 6-8 hrs
• Can have potent effects and excessive fluid and electrolyte loss can result from overdose

Question 13

examples of common irritant (stimulant) laxatives, and how they are used

Answer 13

• Castor oil is a bland plant oil that is converted in the body to an irritant soap; used in small animals, calves and foals
• Anthraquinone is a glycoside derivative found in bisacodyl (Dulcolax®) and senna (Senekot®); human approved products used mainly in small animals

Question 14

what is pancrelipase (pank-aid) and how is it used? what forms does it come in?

Answer 14

• amylase, lipase, protease extracts
• obtained from hog pancreas at slaughter
• powder or tablets
  > Powder appears most effective compared to tablets, capsules and especially enteric-coated tablets
• used in dogs and cats

Question 15

Pancreatic extracts simulate what? what conditions are they used for?

Answer 15

• simulate pancreatic exocrine secretions
• chronic pancreatitis
• pancreatic hypoplasia or insufficiency

Question 16

what conditions are appetite stimulants used in? what species primarily?

Answer 16

in chronic renal failure, cancer, heart failure; primarily in cats

Question 17

commonly used appetite stimulants

Answer 17

• Cyproheptadine (generic)
• Diazepam (Valium®)
• Mirtazapine (Remeron®)

Question 18

mechanism of action of cyproheptadine (generic)? use and results?

Answer 18

• an antihistamine with antiserotonin effects
• postulated to inhibit serotonin receptors controlling appetite in hypothalamus
• used to stimulate appetite in anorexic cats; results usually poor

Question 19

mechansim of action of diazepam (valium) as an appetite stimulant? use and duration of efects?

Answer 19

• Proposed GABA affects on inhibition of satiety center
• Can be useful in anorectic cats, horses ???
• Results very short lived in cats following IV administration
• Potential for idiosyncratic hepatopathy in cats following oral administration of diazepam

Question 20

Mirtazapine (Remeron®) mechanism of action and uses as an appetite stimulant

Answer 20

• blocks several neurotransmitters (NE, 5-HT) to produce appetite stimulation
• blocks presynaptic alpha2 receptors to increase central NE activity, and
  blocks 5-HT3 receptors centrally, both producing stimulation of appetite
• also capable of antiemetic effects
• used in dogs, but mainly cats
• limited studies in vet medicine to date

Question 21

drugs used for Inflammatory Bowel Disease

Answer 21

• Sulfasalazine (Azulfidine®)
• Azathioprine
• Cyclosporine (Atopica®)

Question 22

what is sulfasalazine and what is its use?

Answer 22

• combination of sulfapyridine and 5-aminosalicylic acid; colonic bacteria cleave two moieties
  > 5-ASA is largely not absorbed
• new agents (Mesalamine; 5-ASA) lack sulfa moiety
• used in idiopathic ulcerative colitis in dogs and cats

Question 23

how does Azathioprine work and what does it do? possible effects?

Answer 23

• an immunosuppressive drug used to treat dogs with IBD
• tablets; affects T-cell activity; possible diarrhea and bone marrow effects

Question 24

Cyclosporine mechanism of action and uses?

Answer 24

• suppresses T-cell mediated activity
  > reduces IL-2 and other lymphokines
• used to treat perianal fistulas
• also used for diarrhea caused by inflammatory bowel disease

Question 25

common drugs used for hepatic disease

Answer 25

• Ursodiol (Actigall®)
• S-adenosyl methionine (Denosyl®, Denamarin®, Zentonil®)
• Silybin

Question 26

what is ursodiol? what does it do? what are its uses?

Answer 26

• available as tablets
• ursodeoxycholic acid is a naturally-occurring bile acid
• acts as a choleretic
  > promotes secretion of a hydrophilic (watery) bile by hepatocytes
• promotes absorption of fats
• suppresses hepatic secretion of cholesterol - uses in dogs and cats include:
  > reducing the accumulation of toxic bile salts in hepatobiliary disease
• dissolution of cholesterol gallstones
• also has laxative properties

Question 27

S-adenosyl methionine - what is it? what is its mechanism of action and uses? what is another similar product that is sometimes used in combination?

Answer 27

• low risk veterinary health product; nutraceutical
• S-AMe is important in several liver biochemical pathways that provide
  protection to the liver including detoxification reactions
  > anti-oxidant promoting effects
• liver disease and other oxidative injury
• Silybin (Milk Thistle) also used similarly and combined with S-AMe in Denamarin®