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Pharmacology > Lecture 13: Cholinergic Antagonists > Flashcards

Lecture 13: Cholinergic Antagonists Flashcards

1
Q

How does a neuromuscular blocking agent generally work

A

Blocks the binding site for ACh on Nm receptor

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2
Q

What drugs are commonly used for NMJ blockade

A

Atracurium
Pancuronium and vercuronium bromide- cats and dogs only

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3
Q

T or F: all uses for atracurium are labeled use

A

False, all extra label

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4
Q

What’s are the indicated uses for atracurium besylate

A
  1. Paralyze dogs, cats, small mammals and horses
  2. Intraurethral administration for blocked male cats- relaxes urethral musculature
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5
Q

How is atracurium administered

A

IV

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6
Q

What is the distribution of atracurium

A

Undefined

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7
Q

How are the NMJ blockade drugs metabolized, which one is special and why

A
  1. Pancuronium and vecuronium via plasma esterases
  2. Atracurium spontaneously breaks down
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8
Q

You need to paralyze an animal for a procedure or unblock a male cat. The patient has renal and liver insufficiency which drug are you choosing and why

A

Atracurium because it spontaneously breaks down unlike pancuronium and vercuronium which are broken down via plasma esterases that are produced by the liver

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9
Q

How long do the effects of NMJ blockers last

A

25-30 minutes

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10
Q

__is extended by 15 minutes in dogs when maintained on sevoflurane

A

Atracurium

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11
Q

How is pancuronium eliminated

A

Renal

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12
Q

How is vecuronium eliminated

A

Renal and hepatic

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13
Q

What is the order of NMJ blockade

A
  1. Skeletal muscles become weak, flaccid and then paralyzed
  2. Small muscles
  3. Large muscles
  4. Laryngeal, abdominal, and intercostal muscles
  5. Finally respiratory muscles

**recovery in opposite direction so breathe first

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14
Q

What do you reverse NMJ blockade with

A

Acetylcholinesterase inhibitor, particularly neostigmine

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15
Q

How does neostigmine reverse NMJ blockade

A

Competitive antagonist for acetylcholinesterase, therefore ACh can build up concentration in cleft and outcompete atracurium for binding site at Nm receptor

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16
Q

What type of drug is atropine sulfate

A

Cholinergic antagonist

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17
Q

What are the labeled uses for atropine sulfate

A
  1. Pre-anesthetic to reduce bronchial secretions- improve airway
  2. Sinus bradycardia, sinoatrial arrest, incomplete AV blocks
  3. Differentiate vagally mediated bradycardia vs primary
  4. Treatment for cholingeric agonist toxicity
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18
Q

What receptor does atropine antagonize/ pharmacodynamics

A

Competitive antagonist of M receptors

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19
Q

How do you differentiate between vagally mediated bradycardia vs primary

A

Administer atropine sulfate if vagally mediated should respond because atropine decrease PNS function, but primary involves SNS and PNS and therefore no response if primary

20
Q

What is the absorption of atropine sulfate

A

High bioavailability by many routes

21
Q

What is the distribution of atropine sulfate

A

Very wide, including CNS, milk and placenta

22
Q

How is atropine sulfate metabolized

A

Hepatic

23
Q

How is atropine sulfate excreted and what is the t 1/2

A

Urinary, t1/2= 50 minutes

24
Q

Why is the half life for atropine sulfate clinically relevant

A

Atropine is used in cardiac arrest but usually only once due to 50 minutes half life. If given often will increase concentration rapidly and can result in death of patient

25
Q

Very low does of atropine around 0.02mg/kg IV will be used for what and cause what

A

Preanesthetic use to cause dry mouth and decrease sweating

26
Q

0.04mg/kg IV dose of atropine is use for what

A

Cardiac arrest situations to increase HR

27
Q

What are the adverse effects of atropine sulfate

A
  1. Dry mouth
  2. Decreased bronchial secretions
  3. Arrhythmias
  4. Decreased GI motility
28
Q

What can be a negative side effect in cattle if atropine is used as a premed

A

Postoperative rumen atony

29
Q

What is a negative side effect of atropine use in horses

A

Colic

30
Q

How does atropine sulfate effect the eyes

A
  1. Block iris sphincter- dilation
  2. Absent PLR
  3. Absent accommodation
  4. Dry eyes
  5. Intraocular pressure increases
31
Q

What are the indicated uses for atropine on the eyes

A
  1. Pain secondary to uveal or corneal diseases
  2. Dilation during intraocular surgery
  3. Synechiae breakdown during uveitis
32
Q

How long does dilation of the eyes last with atropine

A

> 100hrs in many species

33
Q

What drug should be used in place of atropine for ophthalmic exams

A

Tropicamide- recovery within 12 hours

34
Q

Ophthalmic atropine can cause __ in horses

A

Colic

35
Q

What is glycopyrolate

A

Synthetic version of atropine

36
Q

What is the labeled use for glycopyrolate

A

Premed for dogs and cats

37
Q

What are the extralabel uses for glycopyrolate

A
  1. Premed in ferrets and small mammals
  2. Bradycardia
  3. Counteract cholinergic effects of imidocarb in horses
38
Q

What are the pharmacokinetics of glycopyrolate

A

Quaternary amine so reduced Vd compared to atropine

Doesn’t cross CNS, placenta or milk

39
Q

In a pregnant animal would would you want to use glycopyrolate or atropine and why

A

Glycopyrolate because doesn’t cross into placenta or milk

40
Q

What is oxybutynin chloride indicated extra label for

A

Treatment of detrusor hyperrflexia in dogs and cats

41
Q

How id oxybutynin chloride given

A

Oral

42
Q

What is the bioavailability of oxybutynin chloride

A

Well absorbed in GI

43
Q

What is the distribution of oxybutynin chloride

A

Everywhere, triple bond makes drug very non-polar

44
Q

How is oxybutynin chloride metabolized

A

Liver

45
Q

How is oxybutynin chloride excreted

A

Urinary

46
Q

What are the side effects of oxybutynin chloride

A

Tachycardia, increase IOP

47
Q

What are some contraindications for oxybutynin chloride

A
  1. Blocked pets
  2. Tachycardia
  3. Glaucoma

Pharmacology (14 decks)

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