Equine GI Pharm

Question 1

According to the DACVS what is the most common IV prokinetic for the management of post operative ileus

Answer 1

lidocaine

Question 2

what are some advantages of using lidocaine pre and intraoperatively

Answer 2

• decreases MAC
• increased smooth muscle contraction in duodenum
• anti inflammatory and analgesic properties
• aids in prevention of post operative ileus

Question 3

what patients should you avoid intraoperative use of lidocaine

Answer 3

horses with reduced liver function.

- it is metabolized by the liver and can lead to toxicosis within several hours

Question 4

what are the signs of lidocaine toxicosis

Answer 4

• muscle faciculations
• ataxia
• collapse
• clinical signs resolve quickly (minutes to hours)

Question 5

What is the purpose of the cholinergic agonist

Answer 5

• act to increase the activation of muscarinic receptors in gastrointestinal smooth muscle
• Stimulate contraction of smooth muscle
• promote intestinal motility

Question 6

what is the MOA of neostigmine

Answer 6

• It will inhibit the activity of acetylcholinesterase
• Reduces gastric emptying and jejunal motility in healthy horses
• is NOT recommended for small intestinal ileus and gastric reflux
• it is however the prokinetic of choice for large colon impactions

Question 7

how is neostigmine utilized in foals

Answer 7

can promote passage of gas in foals with severe abdominal distension and NO displacement or obstruction of colon

Question 8

what is the primary prokinetic effect of metoclopramide in horses

Answer 8

Activation of 5-HT receptors

Question 9

T or F

A Metoclopromide CRI after SI resection and anastomosis can help to lessen severity or avoid ileus

Answer 9

True

• in one study gastric reflux volume was only 2 L compared to 66 L in those not treated

Question 10

what are some adverse side effects from metoclopramide

Answer 10

• extrapyramidal effects secondary to dopamine inhibition in the CNS
• behavior changes (sedation and excitation)
• restlessness or muscle spasms

Question 11

in a horse with suspected metaclopramide toxicity what drug should be given for treatment

Answer 11

diphenhydramine

Question 12

with regaurds to adverse side effects, how might cisapride be recommended over metoclopramide

Answer 12

they are both 5HT antagonists, however cisapride has NO antidopaminergic effects like metoclopramide

Question 13

what is the most widely used “motilide” in equine medicine

Answer 13

Erythromycin

Motilide comes from the combination of motilin and macrolide, which describes the class and effect of this antibiotic

Question 14

Erythromycin, the most commonly used motilide, is second only to what drug for it’s prokinetic effects in our equine species

Answer 14

Lidocaine

Question 15

what is the primary use for erythromycin

Answer 15

cecal impactions

Question 16

why should adult horses only receive IV administration of erythromycin, and not PO

Answer 16

PO administration increases the risk of colitis

Question 17

would the presence of GI Dz reduce the prokinetic effect of erythromycin in horses?
if so….. how?

Answer 17

• Motilin receptors are found predominately in the horses duodenum and jejunum, after that there is a decrease in motilin receptors.
• These receptors are particularly susceptible to ischemic injury and intestinal distension, which in turn can cause damage to these receptors
• resulting in reduced effectiveness of erythromycin

Question 18

What would the Take Home message be for post opperative ileus

Answer 18

• effective pain management is important (NSAIDs preferential)
• lidocaine helps with inflammation and analgesia although still clinician dependent
• others drugs are used at the discretion of clinician

Question 19

what 2 H2 antagonists are typically used in horses, and which one is more efficatious

Answer 19

• ranitidine
• cimetidine

Ranitidine is preferred to cimetidine

Question 20

besides H2 antagonistic effects, what other condition is cimetidine used to treat

Answer 20

melanomas in horses

Question 21

what unique characteristic should be considered when prescribing a proton pump inhibitor

Answer 21

• they require special formulation for absorption in SI (alone are unstable in acidic enviroment)
• they take ~3 days to reach steady state

Question 22

what is the MOA of sucralfate in horses

Answer 22

• binds directly to the ulcer
• creates a physical barrier to protect it from stomach acids to prevent further damage
• Promotes bicarb production

Question 23

what are some adverse side effects to be aware of with sucralfate administration in horses

Answer 23

• constipation
• xerostoma (dry mouth)
• flatulance
• headache