How does Atropine cause an initial decrease in HR?
stimulation of central vagal nucleus in medulla
This anticholinergic is associated with decreases in GI and ruminal motility in horses and ruminants
Atropine
*can lead to ruminal stasis & colic (ileus)
When comparing species sensitivities to atropine toxicity:
1) herbivores vs. carnivores
2) least resistant?
3) why are cats, rats, and rabbits more resistant?
1) herbivores are more resistant
2) pigs are least resistant
3) possess atropinase
An anticholinergic that doesn’t penetrate the BBB as easily as atropine? Why doesn’t it penetrate as well?
Glycopyrrolate; larger molecular size
Acepromazine has an effect on this neurotransmitter
Dopamine (antidopaminergic…increases turnover rate)
Ace is involved in what receptor blockade? What does it lead to?
alpha-1; vasodilation/hypotension (anti-epinephrine)
How can Ace cause hypothermia?
depletion of catecholamines from hypothalamus (thermoregulatory center) and peripheral vasodilation
Name 3 important systemic effects of ace? (think heart, gut, cells)
antiemetic (good against opiate-induced vomiting)
antiarrhythmic (stabilizes myocardium)
Antihistaminic (acts on mast cells)
T/F: though it lacks analgesic effects itself, ace can potentiate the analgesic effects of other drugs
True
What drug should not be used to reverse droperidol-induced hypotension
epinephrine
What two drugs combine to make innovarVet and what word is used to describe that drug? Use?
1) Droperidol & Fentanyl
Neuroleptanalgesic (tranquilizer & analgesic)
Vicious Dogs
Describe the 3 MOA/effects of benzodiazepines
1) stimulate the benzodiazepine receptors and potentiate GABA–>increases Cl influx into cell to cause hyperpolarization
2) depresses limbic system (anxiolytic)
3) central muscle relaxation
Purpose of propylene glycol vehicle for Dizepam?
increases solubility (Diazepam is usually not H2O soluble)
Best anesthetic adjunct for critical patients due to its minimal cardiovascular effects?
diazepam
Which two drugs combine to make telazol?
Zolazepam & Tiletamine
Benzodiazepine antagonist
Flumazenil
Sedatives are ______ receptor ______
alpha-2 receptor AGONISTS
3 general anesthetic effects of the alpha-2 agonists
Sedation
Analgesia
Muscle relaxation
How is the A2:A1 ratio related to potency?
Which drug has:
1) highest ratio
2) lowest ratio
the higher the ratio, the more potent the drug
1) Medetomidine/Dexmeditomidine
2) Xylazine
Name 2 important systemic effects associated with Xylazine
1) increases urine output (inhibits ADH…esp. ruminants)
2) increases intrauterine contraction and pressure (premature parturition)
Describe Xylazine’s impact on the cardiovascular system
biphasic effect on BP:
initial HYPERtension, followed by HYPOtension
Sensitizes myocardium (arrythmias likely!)
How does Xylazine cause a biphase BP response?
Initial stimulation of post-synaptic A2 receptors
followed by stimulation of pre-synaptic A-2 receptors
This drug can cause hypoxemia in sheep and calves
Xylazine
Describe the species variations with xylazine:
1) ruminants vs. horses?
2) least sensitive?
3) list spp. from least to most sensitive
1) ruminants are 10X more sensitive than horses
2) pigs are least sensitive (need highest dose)
3) Pigs > horses > dogs > cats > ruminants
It’s important to let a horse calm down before giving ________
Xylazine (due to high circulating catecholamines after traveling…can lead to sudden death)
Which a-2 receptor agonist is only approved for horses?
Detomidine
Major difference between the IV and sublingual preparations of detomidine?
Sublingual preparation will not have analgesic effects
Which drugs would be indicated for prevention of the oculocardiac reflex during surgery?
Anticholinergics (atropine, Glycopyrrolate)
2 drugs that can treat Acepromazine-induced hypotension
Phenylephrine
Methoxamine
Which drug should be used cautiously in horses during standing procedures and why?
Diazepam–can cause profound relaxation and recumbency
Which benzodiazepine has the longest duration of action?
Zolazepam
Which sedatives are associated with vomiting in cats/dogs?
Xylazine; Medetomidine
3 contraindications for xylazine/sedatives in general
1) pregnancy
2) urethral obstruction
3) cardiac aberration
This sedative is the best choice for diagnostic procedures (require deep sedation/immbolization but not general anesthesia)
Medetomidine
Medetomidine + ________ can provide short-term anesthesia in small animals and zoo/wildlife spp.
Ketamine
A unique feature of this sedative is its use as a CRI
Dexmeditomidine
A benefit of Romifidine (compared to xylazine & meditomidine)
causes less ataxia and sedation (horses can maintain higher head position)
*good for dentals!
Name 3 alpha-2 antagonists
Yohimbine
Tolazoline
Atipamezole
Concerning the 3 a-2 antagonists, which:
1) has the greatest selectivity for a-2
2) has least selectivity for a-2
1) Atipamezole
2) Tolazoline
Two major side effects associated with Tolazoline?
Tachycardia GI distress (stimulates GI musculature)
Severe toxicity of llamas and camels is associated with which a2 antagonist?
Tolazoline
*Llamas and camelids are sensitive to Tolazoline
Best drug choice if you’re trying to:
1) reverse sedation (CNS effects)
2) reverse ruminal hypomotility
1) atipamezole
2) Yohimbine & Tolazoline
Which pre-anesthetic is useful for large animals when other sedatives/tranquilzers fail?
Chloral Hydrate
This sedative is characterized by “latent action” (name it and describe why)
Chloral Hydrate
it has to form an active metabolite (Trichloroethanol)
**it’s active metabolite exerts the anesthetic effects
What benefit does magnesium sulfate offer when combined with Chloral hydrate?
enhances muscle relaxation (has neuromuscular blocking effects)
