GI drugs 2 pt 2 Flashcards
categories of drugs used as laxatives and cathartics
- Emollient Laxatives (lubricants)
- mineral oil
- white petrolatum - Simple Bulk Laxatives
- methylcellulose
- psyllium seed - Stool Softeners (Surfactants)
- Docusate sodium - Hyperosmotic Cathartics (salts, sugars)
- Irritant (Stimulant) Laxatives
- Castor oil
- Anthraquinone
how do emmollient laxatives work? what are common examples
Lubricating and fecal softening properties
- mineral oil
- white petrolatum
mineral oil use, pros and cons?
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
white petrolatum use? often combined with what?
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
how do simple bulk laxatives work? what are some examples? what species are they used in?
- 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
example of commonly used stool softener
Docusate sodium (Anti-Bloat®)
how do stool softeners (surfactants) work? primary uses?
- 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
Hyperosmotic Cathartics (salts, sugars); how do they work, what is their use? how are they administered? what do animals given this also need?
- 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
salts used as hyperosmotic cathartics
- Magnesium sulfate (Epsom salts)
- Sodium sulfate (Glauber’s salt)
sugars used as hyperosmotic cathartics?
- Mannitol and sorbitol
- Lactulose (Cephulac®)
> synthetic disaccharide
what is lactulose and when is it used?
- synthetic disaccharide
- used as hyperosmotic cathertic for dogs, cats, some birds
- also used in hepatic encephalopathy
Irritant (Stimulant) Laxatives; how do they work? how quickly?what can occur with overdose?
- 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
examples of common irritant (stimulant) laxatives, and how they are used
- 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
what is pancrelipase (pank-aid) and how is it used? what forms does it come in?
- 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
Pancreatic extracts simulate what? what conditions are they used for?
- simulate pancreatic exocrine secretions
- chronic pancreatitis
- pancreatic hypoplasia or insufficiency
what conditions are appetite stimulants used in? what species primarily?
in chronic renal failure, cancer, heart failure; primarily in cats
commonly used appetite stimulants
- Cyproheptadine (generic)
- Diazepam (Valium®)
- Mirtazapine (Remeron®)
mechanism of action of cyproheptadine (generic)? use and results?
- an antihistamine with antiserotonin effects
- postulated to inhibit serotonin receptors controlling appetite in hypothalamus
- used to stimulate appetite in anorexic cats; results usually poor
mechansim of action of diazepam (valium) as an appetite stimulant? use and duration of efects?
- 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
Mirtazapine (Remeron®) mechanism of action and uses as an appetite stimulant
- 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
drugs used for Inflammatory Bowel Disease
- Sulfasalazine (Azulfidine®)
- Azathioprine
- Cyclosporine (Atopica®)
what is sulfasalazine and what is its use?
- 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
how does Azathioprine work and what does it do? possible effects?
- an immunosuppressive drug used to treat dogs with IBD
- tablets; affects T-cell activity; possible diarrhea and bone marrow effects
Cyclosporine mechanism of action and uses?
- 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
common drugs used for hepatic disease
- Ursodiol (Actigall®)
- S-adenosyl methionine (Denosyl®, Denamarin®, Zentonil®)
- Silybin
what is ursodiol? what does it do? what are its uses?
- 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
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?
- 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®
