Cholinergics II and Muscle Blockers Flashcards

1
Q

What is the mechanism of action

of Indirect Cholinergic Agonists?

A

Block acetylcholinesterase thereby increasing the amount of Ach in the synapse

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2
Q

Why are anticholinesterases called “Indirect” Cholinergic Agonists?

A

They do not directly activate the Cholinergic receptors,

but rather,

they increase the actions of endogenous Ach

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3
Q

What is the effect of Indirect Cholinergic Agonists on vascular smooth muscle (and blood pressure)?

A

No effect

because they increase the amount of

endogenous Ach in the synapse

and there is no endogenous Ach

at smooth muscles because there is no innervation!

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4
Q

How much do Indirect Cholinergic Agonists

affect muscarinic and nicotinic receptors?

A

At low-moderate doses they affect muscarinic.

At high concentration they activate nicotinic receptors

and thus muscle contractions, fasciulations and convulsions

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5
Q

What are other names for “Indirect Cholinergic Agonists?”

A

Indirect Cholinomimetics

Anticholinesterases

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6
Q

What are the important Indirect Cholinergic Agonists we need to know?

A

Neostigmine

Physostigmine

Donepesil

Sarin

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7
Q

Name the durations of actions of:

Physostigmine

Neostigmine

Donepezil

Sarin

A

Physostigmine: .5 - 2 hours

Neostigmine: .5 - 2 hours

Donepezil: 24 hours

Sarin: > 4 days

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8
Q

If you needed to prescribe a short-acting anticholinesterase, what would your choices be?

A

Neostigmine

Physostigmine

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9
Q

What do the key indirect cholinomimetics treat?

Neostigmine

Physostigmine

Donepezil

A

Neostigmine: Myasthenia Gravis, Paralytic Ileus

Physostigmine: Glaucoma (miotic)

Donepezil: Alzheimers

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10
Q

What Anticholinesterase would you prescribe to treat Alzheimer’s

A

Donepezil

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11
Q

What anticholinersterase would you prescribe for a patient with glaucoma

A

Physostigmine

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12
Q

What Indirect Cholinomimetic would you prescribe to treat Myasthenia Gravis or Paralysic Ileus?

A

Neostigmine

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13
Q

What Anticholinesterase

is used to diagnose Myasthenia Gravis?

Why is this the best anticholinesterase for this purpose?

A

Edrophonium

Because its Duration of action is 5-15 minutes

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14
Q

Which reversible anticholinesterase

can cross the blood brain barrier?

A

Physostigmine

Donepezil

(Neostigmine cannot cross BBB)

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15
Q

If you are prescirbing Neostigmine to treat Myasthenis Gravis, what do you do about

unwanted muscarinic receptor activiation?

A

Give Atropine to control these side effects

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16
Q

What anticholineresterase can reverse the paralytic effects of Vecuronium?

(What is the “antidote”)

A

Neostigmine

17
Q

Your patient just got out of abdominal surgery

and now has a paralytic ileus.

How do you treat this?

A

Neostigmine

18
Q

How does Donepezil treat Alzheimer’s Disease?

A

Alzheimer’s patients have decreased cholinergic function

due to cholinergic neuron damage and death,

leading to problems with memory and cognition.

Donepezil crosses the BBB

decreases aceylcholinesterase by 40%

and thereby increases ACh at CNS synapses.

HOWEVER: does not prevent progression!

19
Q

How do Sarin

and other organophosphates like Parathion

get into the body?

A

They are very volatile liquids and

are lipid soluble and enter through any exposure to skin

20
Q

What are the initial symptoms

of organophosphate poisoning?

(like Sarin or Parathion)

A

SLUDGE:

Salivation

Lacrimation

Urination

Defecation

GI Distress

Emesis

Basically if you have a patient who has stuff pouring out of every orifice, think organophosphate poisoning!

21
Q

What are late symptoms of organophosphate poisoning?

A

bronchodilation, bradycardia, hypotension, pulmonary edema

twitching

respiratory paralysis (skeletal muscles: diaphragm, etc)

Ataxia, confusion, convulsions, coma, death

22
Q

A 25 year old landscaper is brought in on an ambulance.

He loos very sick, vomiting, drooling, with watery eyes.

He smells terrible and the EMT says that he urinated and defecated in his pants and was moaning about his stomach hurting.

What are you thinking?

A

Organophosphate poisoning

23
Q

What is the antidote to nerve gas/Sarin gas?

A

Atropine to block excess muscarinic activation

plus

Pralidoxime to reactivate acetylcholinesterase.

24
Q

What is the only available ganglionic blocker and what is it used to treat and why?

A

Trimethaphan

Used to treat acute dissecting aortic aneurysm

Used to allow physician to completely control BP

by blocking physiologic reflexes

25
Q

Does Trymethaphan control the

sympathetic or

parasympathetic systems?

A

Both

because it blocks gangionic nicotinic receptors.

But it has no effect on skeletal muscles.

26
Q

What are skeletal muscle blockers and how are they used?

A

Skeletal Muscle Nicotinic Antagonists

used to temporarily paralyze muscles for surgery

27
Q

What are the two types

of skeletal muscle blockers and how to they work?

A

Depolarizing: agonist that opens channel gate,

but then blocks the channel

Nondepolarizing: Prevents the channel gate from opening, thus a competitive antagonist.

28
Q

Is vecuronium a nondepolarizing or depolarizing skeletal muscle blocker?

What is it used for?

A

Nondepolarizing

Used to paralyze skeletal muscles for 1-1.5 hrs during surgury.

Highly charged.

Does not cross BBB.

NOT an anesthetic!!!!

29
Q

Your patient is out of surgery

and you want to reverse the effect of Vercuronium.

What can you use?

A

Neostigmine

increases Ach levels

and overcomes the competitive blockade

at the nicotinic receptors.

Atropine often added as well.

30
Q

Is succinylcholine

a depolarizing or nondepolarizing muscle blocker?

What is it used for?

A

Depolarizing

Used in preparation for endrotracheal intubation

because it has rapid onset and is short acting.

31
Q

You have given your patient succinylcholine

to paralyze the muscles to trach him,

but it has been over 30 minutes

and the effect has not worn off.

What is happening and what do you do?

A

Some patients (rare) have atypical cholinesterase.

Usually succinylcholine is metabolized by acetylcholinesterase, but this this case, it is not readily metabolized.

You cannot use neostigmine as an antidote.

(Presumable you would just wait it out.)

32
Q

What is a major contraindication

for use of succinylcholine?

A

It increases K+ from the muscle

causing hyperkalemia and cardiac arrhythmia.

Contraindicated if patient has renal failure, is a burn patient, or multiple trauma, or has large areas of denervated muscle.

Alternative: rocuronium (duration of activity: 20-40 mins)

“Succ sucks, roc rocks”

33
Q

What is the mechanism of action

of Botulinum Toxin?

A

It is a neurotoxin found in Botulinus anaerobic bacteria

that blocks ACh release by cleaving SNAP-25

thereby paralyzing muscles.

34
Q

What are the therapeutic uses of Botulinum Toxin

A

Botox is used for:

Cosmetic surgery

Chronic Migraine

Local IM injection for blepharospasm, hemifacial spasm

and spasms in muscular diseases.

35
Q

What neurotransmitters do Botulinum toxin target?

A

It is specific for the presynaptic terminals

of cholinergic neurons.

36
Q

Your 55 year old female patient

suffers from migraines about 7 days each month

and asks you to prescribe Botox shots.

Should you?

A

FDA says Botox shots are for patients with a migraine

most days of the month.

Shot is administered every 12 weeks

in areas around the head and neck.

Adverse effects: neck pain and headache.