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Pharmacology - Autonomics > Neuromuscular and ganglionic blockers > Flashcards

Neuromuscular and ganglionic blockers Flashcards

1
Q

Definition of Ganglionic Blockers (GBs)?

A

nicotinic receptor antagonists

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2
Q

What do GBs do?

A

block reflexes- baroreceptor, pupillary

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3
Q

Examples of GBs…

A

Trimethaphan-hypotension for surgery

Mecamylamine-in severe hypertension, smoking cessation, Tourette’s Syndrome

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4
Q

Natural state of vascular smooth muscle tone in body

A

Sympathetic > Parasympathetic

blockade=vasodilation

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5
Q

Natural state of all other ANS function

A

Parasympathetic > Sympathetic

blockade=tachycardia

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6
Q

What are the two ways to block Ach transmission?

A

pre-synaptic: decrease Ach formation or release, increase metabolism
post-synaptic: block cholinergic receptors

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7
Q

Which one is the clinical use?

A

block cholinergic receptors

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8
Q

limitation of neuromuscular blockers?

A

quarternary ammonium->only peripheral use

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9
Q

What is the function of neuromuscular blockers?

A

to relax skeletal muscles needed in:

surgery, orthopedic procedures, bronchoscopy, artificial respiration/intubation

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10
Q

First clinically used neuromuscular blockers?

A

curare: D-tubocurarine is the major active alkaloid in it

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11
Q

What is the purpose of neuromuscular blockers?

A

allow for using different classes of drugs for muscle relaxation and anesthesia

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12
Q

Train of Four (TOF)?

A

used to monitor the strength of neuromuscular blockage

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13
Q

TOF ratio can be used for…

A

determine at the end of procedure if the patient can be extubated

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14
Q

When extubation can occur?

A

TOF ration >0.7

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15
Q

What is non-depolarizing blocking agent?

A

competitively blocking the binding of ACh to its receptors

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16
Q

What is depolarizing blocking agent?

A

depolarizing the sarcolemma of the skeletal muscle fiber-> persistent depolarization makes the muscle fiber resistant to further stimulation by ACh

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17
Q

Non-depolarizing vs. depolarizing agent

A

“Fade” vs. no “Fade” until TOF ratio

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18
Q

What determines if the patient’s muscles are sufficiently blocked?

A

the number of twitches: procedures are performed when patient responds with 1-2 twitches
under this condition, blockade can be quickly reversed

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19
Q

Sequence of muscle paralysis under neuromuscular blockers?

A

muscles of eye, speech, then fingers, toes, limbs, lastly intercostals and diaphragm

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20
Q

Sequence of muscle paralysis mimics…

A

Guillain-Barre syndrome

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21
Q

Example of depolarizing agent (nicotinic Ach receptor agonist)

A

Succinylcholine

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22
Q

Characteristics of Succinylcholine

A

short duration=5-10mins

metabolized by butyrylcholinesterase to choline, which incases BP

23
Q

Benefits of using Succinylcholine

A

fast onset, short duration of action

24
Q

When do you use Succinylcholine?

A

trauma care, INTUBATION, electro-convulsant therapy

25
Q

When not to use Succinylcholine?

A

patients with HYPERKALEMIA -cause cardiac arrest

26
Q

Examples of non-depolarizing agents (curare-like, nicotinic Ach receptor antagonist)

A

Pancuronium (180mins)
Vecuronium, Atracurium (30-40mins)
Trimethaphan (short)
all easily reversible->widely used

27
Q

mechanism of Succinylcholine?

A

nicotinic Ach receptor agonist->persistant opening of Na+ channel->prevent repolarization->no further action potentials occurs

28
Q

What is Rocuronium?

A

non-depolarizing neuromuscular blocker (muscle relaxant)

29
Q

There are two ways to reverse Rocuronium actions.

A

use AchE inhibitor like Neostigmine

use Sugammadex- sequester Rocuronium by directly binding to it

30
Q

The function of AchE inhibitors is like…

A

a cholinergic agonist
its function relies on the presence of Ach-> so little effect on function of M3 receptors in blood vessels as no Ach in blood stream anyway

31
Q

Two types of cholineesterases

A

AchE in synapses w/. high affinity for Ach

BuchE in plasma, metabolize Succinylcholine and procaine

32
Q

3 classes of AchE inhibitors

A

Carbamates
Organophosphates
Quaternary ammonium alcohols

33
Q

How Carbamates work?

A

temporarily covalent bound to AchE

reversible, dissociate in 0.5-8hrs

34
Q

1st example of Carbamates

A

Physostigmine:
tertiary amine, enters CNS
for atropine overdose
Clinical: glaucoma, Alzheimer’s Disease

35
Q

2nd and 3rd examples of Carbamates

A

Neostigmine and Pyridostygmine
quartanary amine, peripherally restricted
reveal of NMB, post-operative ileus, bladder distention
Pyrido=less side effect, longer duration
Clinical: Myasthenia gravis

36
Q

How Organophosphates work?

A

irreversibly covalent bound to AchE -> long duration of action
Clinical: glaucoma- not commonly used

37
Q

What other uses of Organophosphates?

A

as insecticides and nerve gas (sarin)

38
Q

What is Pralindoxime?

A

antidote for pesticide or never gas (AchE inhibitors) poisoning

39
Q

When to give Pralindoxime?

A

it is only effective within a few hours of exposure to insecticides

40
Q

What is Organophosphate Aging?

A

once organophosphate covalently bound to AchE, the bond will be hydrolyzed and this step is IRREVERSIBLE, called aging.

41
Q

Mnemonics for symptoms of AchE inhibitor poisoning is…

A 
D=diarrhea(M3)
U=urination(M3)
M=miosis(M3)
B=bronchospasm(M3)
B=bradycardia(M2)
E=excitation of skeletal muscles and CNS(Nm)
L=lacrimation(M3)
S=sweating(M3)
S=salivation(M3)
42
Q

The trigger word for AchE inhibitor poisoning is…

A

farmer

43
Q

How quaternary ammonium alcohol work?

A

binds non-covalently, reversible

44
Q

Example of quaternary ammonium alcohol

A

Edrophonium:
short action(5-10mins)
Clinical: used for diagnosis of Myasthenia Gravis(MG) and to distinguish it from Lambert Eaton MG

45
Q

Clinical effect of Edrophonium in MG

A

MG patient exercise-> worsen muscle strength-> give Edrophonium-> improves muscle strength

46
Q

What is Lamber Eaton MG?

A

Abs against calcium channels rather than Abs against Nm in MG

47
Q

Clinical effect of Edrophonium in Lamber Eaton MG

A

Lamber Eaton MG patient exercise-> improves muscle strength-> give Edrophonium-> no effect

48
Q

What is cholinergic crisis?

A

overdose of AchE inhibitors-> overstimulation-> paralysis-> weak muscles

49
Q

How to distinguish MG from cholinergic crisis?

A

Edrophonium-> no effect in CC

-> improves muscle strength in MG

50
Q

Contraindications to use of parasympathomimetic drugs:

A 
Asthma and COPD
Coronary deficiency
Peptic ulcer->increase acid secretion
Obstruction of urinary or GI tract
Epilepsy
51
Q

Cholinergic and adrenergic centers in CNS

A

brain stem and nucleus basal is of Meynert ->Ach

locus coeruleus -> NE

52
Q

Alzheimer Disease

A

loss of cholinergic neurons in brain due to improper processing of beta-amyloid proteins->toxicity->apoptosis of neurons

53
Q

AchE inhibitors in Alzheimer disease

A

Donepezil, Rivastigmine (carbmate), Galanthamine (from daffodil):
reversible binding to AchE
enhance cognitive ability
lose effect as Ach decreases due to Ach-producing neurons die
DO NOT slow progression of AD

54
Q

How to increase Galanthamine bioavailability?

A

give inhibitors of CYP3A4, CYP2D6

Pharmacology - Autonomics (2 decks)

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