GI pharmacology 2

appetite stimulants

anorexia common in disease - malnutrition will exacerbate disease

• liquid enteral alimentation/ warm palatable food frequently

• drugs = 

• benziodiazapines e.g diasepam, oxazepam = increase GABA - resulting anti-serotonergic effect depresses atiety centre in hypothalamus 

• cryroheptadine = serotonin and histamine antagonist - supresses satiety centre in hypothalamus 

• glucocorticoids e.g prenisolone and dexamethazone = mechanism of action unknown 

probiotics definition

sample of normal intestina microbes

prebiotics definition

substrates that promote normal intestinal microbes

probiotics/prebiotics

competitive action to reduce pathogenic microbes

has been shown to be effective in domestic species but exact efficacy still unproven

bowel anti - inflammation

sulfasalazine = sulfapyridine and 5-aminosalicyclic acid 

• cleaved by bacteria to release sulfapyridine and salicylate = salicylate has anti-inflammatory effect on bowel mucosa, may inhibit PG synthesis of colonic mucosa, sulfapyridine may cause keratoconjunctivitis sicca

olsalazine = 2 × 5-aminosalicyclic acid 

• as above but less toxic as no sulfapyridine 

tylosin 

• macrolide antibiotic(related to erythromycin)

• suppresses bacterial overgrowth

• inhibits protein synthesis in susceptible bacteria

metronidazole

• anti-protozoa/ anti-bacterial (esp anaerobes)

• suppresses cell-mediated immune reactions 

digestants

pancreatic enzyme supplements

• used in treatment of exocrine pancreatic insufficiency 

• contains lipases, amylase, proteases

• usually administered with acid-inhibitors to prevent destruction of enzymes by stomach

bile acids/ salts

• bile acids stimulate flow of bile

• bile salts emulsify dietary lipid enhancing its digestion and absorption 

urso-deoxycholic acid

in cholestatic liver disease bile acids build up in body

hydrophobic bile acids are toxic to hepato-biliary cell membranes 

urso-deoxycholic acid(UCDA) is hydrophillic bile acid 

• cyto-protective to biliary system 

• inhibits ileal absorption of hydrophobic bile acids

• also immuno-modulatory 

• may modify hepatocyte apoptosis 

lactulose

metabolised by colonic bacteria into organic acids(lactic, formic, acetic)

these acids trap ammonia as ammonium ions which are egested 

used in patients with hepatic encepalopathy to reduce blood ammonia levels 

hepato-biliary cytoprotective agents

S-adenosylmethione(SAMe)

• anti-oxidant

• stabilisation of membrane function

• modulation of cytokie expression

• anti-apoptotic in normal cells

siltmarin

• reactive oxygen species (ROS) scavenger

• anti-inflammatory

• antifibrotic

• increases hepatic protein synthesis

• choleretic - increases secretion of bile

vitamin E

• anti-oxidant

• anti-inflammatory

ruminant GI treatment - general considerations

in oral mediaction of calves/lambs oesophageal groove must be stimulated to ensure drugs bypass developing rumino-reticulum

rumen pH should be 5.5-7 for efficient fermentation

innervation

• extrinsic via vagal afferents

• intrinsic via enteric nervous system 

rumen microbes require

• proper nutrient intake

• normal motility 

ruminant GI treatment - inducing closure of oesophageal groove

warm milk, sodium bicarbonate, copper sulphate

if drugs mixed with these they will bypass rumino-reticulum and pass into abomadum/SI

causes lips of groove to fold over to form continuous tube

ruminant GI treatment - restoring rumen function

cholinergics increase frequency(but not strength) of contractions in rumen atony

opiate antagonists stimulate extrinsic contraction when administered parenterally

rumen fluid transfer of viable ruminal bacteria/protozoa from healthy animal and put into unhealthy animal via stomach tube

ruminant GI treatment - rumen antacids 

e.g aluminium hydroxide, calcium carbonate

can be used to treat mild cases of rumen acidosis

severe cases require parenteral fluid therapy and/or evacuation of ruminal contents

ruminant GI treatment - rumen acidifiers 

e.g vinegar, acetic acid

treat excessive bicarbonate influx from hyper-salivation

used in acute urea poisoning - cconvert ammonia into ammonium thereby reducing absorption and inhibit urease activity of microbes

ruminant GI treatment - viscosity-altering (anti-bloat) agents

e.g mineral/vegtable oil

treatment of frothy(not gassy) bloat

alter surface tension of bubbles allowing them to coalesce and break up

colic treatment

surgical or medical

hypovolaemia/ dehydration

• fluids

pain

• NSAIDs - phenylbutazone(short acting, mild pain) and flunixin meglumine( long acting, severe pain, beware as masks signs)

• opiates - butorphanol (short acting, moderate pain)

medical colic 

spasmodic 

• SI hypermotility/spasms

• anti-spasmodic - butylscopolamine = inhibits M1 muscarinic acetylcholine receptors

• analgesic - metamzole = NSAID

pelvic flexure impaction 

• impaction at narrowing between left ventral and left dorsal colon

• oral fluids for lubrication/ softening of impaction 

flatulent 

• distension

• pain management - opioids, NSAIDs not usually effective except flunixin but beware masking