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Pharmacology Exam 3 (Toy's) > Pharmacolgy of NMJ > Flashcards

Pharmacolgy of NMJ Flashcards

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0
Q

Muscarinic is associated with what nervous system response

A

Rest & digest (parasympathetic)

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1
Q

What are the two cholinoceptors

A
  • muscarinic

- Nicotinic

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2
Q

Nicotinic receptors are associated with nervous system response

A

Excitatory

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3
Q

What is the neurotransmitter at both muscarinic and nicotinic receptors

A

Ach

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4
Q

Characteristic of muscarinic receptors

A
  • G protein linked

- Regulate 2nd messenger production

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5
Q

Where are muscarinic subsets located

A
  • heart
  • airway smooth muscle
  • salivary gland
  • tissues innervated by cholinergic postganglionic nerves
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6
Q

Muscuranic stimulation will cause what type of response (heart, lungs, salivary glands, nervous tissue)

A
  • decrease HR
  • bronchoconstriction
  • increase saliva
  • increased muscle relaxation
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7
Q

Nicotinic characteristics

A
  • selective ligan gated ion channel receptors
  • Cholinoceptor selectivity
  • excitatory mainly, does have inhibitory receptors
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8
Q

Where are nicotinic receptors located

A
  • In PNS cells, postganglionic SNS cells and skeletal muscle endplates
  • N1 @ autonomic ganglia, N2 @ NMJ
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9
Q

Cholinoceptor direct activation Vs. Indirect activation

A
  • Direct activation acts on muscarinic and nicotinic receptors directly.
  • Indirect activation inhibits the hydrolysis of Ach (acts on acetylcholinesterase enzyme)
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10
Q

Where is Ach broken down?

A

NMJ

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11
Q

What drug and/ or neurotransmitter are choline esters?

A

Ach, Succinylcholine

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12
Q

What drug/ neurotransmitters are alkaloids/ amines

A

muscarine, nicotine

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13
Q

What is the effect of a Beta-methyl group at a nicotinic receptor?

A

reduces the potency

methacoline, challenge test; bethanecol, urinary retention

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14
Q

How are esters absorbs (r/t rate of absorption) and distributed? What is the reason for this absorption/ distribution rate rate?

A

-Esters are poorly absorbed and distributed due to hydrophillic properties

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15
Q

What hydrolizes Ach and at what rate?

A

Ach rapidly hydrolyzed by acetylcholinesterase

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16
Q

What hydrolyzes succinylcholine?

A

Pseudocholinesterase

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17
Q

What contributes to ester compounds with longer DOA

A

Greater resistance to acetylcholinesterase (ex. Metacholine 3x more resistant)

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18
Q

What type (structure) of alkaloid is Nicotine. How does it (type) effect its absorption?

A

Tertiary alkaloid, lipid soluble, well absorbed

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19
Q

What type (structure) of amine is Muscarine and how does it effect rate of absorption?

A

Quarternary amine. Less completely absorbed. Decrease lipid solubility. (can still be toxic, eg. certain mushrooms)

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20
Q

(2) Ways(MOA) in which a direct acting, muscarinic cholinoceptor stimulants can work

A
  1. Ach activates muscarinic receptors directly on effector organ
  2. Ach interacts w/ muscarinic receptor on nerve terminal to inhibit release of neurotransmitter (- feedback loop); likely involves 2nd messenger
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21
Q

Nicotinic MOA

A

Depolarization of nerve cells or neuromuscular endplate

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22
Q

Define: Neuromuscular blockade

A

If depolarization of nerve cell becomes prolonged, the response is abolished (neuron stops firing), skeletal muscle relaxes.

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23
Q

Cardiovascular effects of cholinoceptor stimulation

A
  • Decrease HR, contraction, and conduction velocity

- Muscarinic agonist release EDRF (endothelium-derived relaxing factor)

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24
Result of the release of EDRF(endothelium-derived relaxing factor) from muscarinic agonist in small doses vs. large doses
- small doses:Venous & arterial dilation | - large dose: Direct vasoconstriction effect
25
Effect of Cholinoceptor stimulation on CNS
(Think nicotine stimulation w/ CNS) - Nicotine tremor - Stimulation or respiratory center - High levels cause Sz.
26
****What happens with Stimulation of cholinoceptors at NMJ
-Depolarization of endplate (r/t increased permeability to Na+ & K+ ions (caused by nicotine stimulation)
27
How do indirect acting cholinoceptors (stimulants) work?
Inhibit acetylcholinesterase thereby allowing increased concentration of Ach
28
Where is the primary effect of indirect acting cholinomimetics
- AT the active site of the enzyme | - Some have direct action on nicotinic receptors
29
In terms of the amount manufactured, what is the most common use for INDIRECT-acting cholinomimetics
Insecticides
30
How do the therapeutic and industrial structures of INDIRECT-acting cholinomimetics compare
- Differences are in chemical structure and pharmacokinetics. - The pharmacodynamics are almost always the same.
31
3 commonly used groups of INDIRECT-acting Cholinoceptor stimulants (with examples)
1. Organic derivatives of phosphoric acid (organophosphates) 2. Simple alcohols w/ quaternary ammonium group (edrophonium) 3. Carbamic acid esters of alcohol with quaternary ammonium (neostigmine) or tertiary amine group (physostigmine)
32
Characteristic of Organophosphate INDIRECT-acting Cholinoceptor stimulants (with examples)
-Highly lipid soluble, well absorbed by skin - Soman, potent nerve gas - Paratione & malathione insecticides are converted to phosphate derivatives in plants & animals and are better for insecticide use
33
***** Quartenary carbamates vs. tertiary amines (INDIRECT-acting Cholinoceptor stimulants) absorption rates -drug example of each
- Quaternary carbamates (Neostigmine) is poorly absorbed via skin, lungs, PO - Tertiary amines (Physostigmine) are well absorbed (Eserine eye drops) and more readily distributed to CNS
34
How does affinity of INDIRECT-acting Cholinoceptor stimulants effect potency
- differences in potency reflects differences in affinity | - Increase infinity = increased potency (and the opposite)
35
3 MOA of INDIRECT-acting Cholinoceptor stimulants drugs. (Mechanisms in which they inhibit ach-esterase)
1. Reversible inhibition 2. Formation of carbamyl esters (reversible) 3. Irreversible inactivation
36
Uses for Edrophonium
- Skeletal muscle relaxant reversal | - Tensilon Challenge (Myasthania gravis/ cholinergic crisis dx.)
37
Why are drugs that form carbamyl esters effective at inhibiting ach-esterase. (what makes them good INDIRECT-acting Cholinoceptor stimulants)
Carbamylated Ach-esterase can't hydrolyze Ach
38
Drugs that are Carbamyl esters
1. Neostigmine 2. Pyridostigmine 3. Physostigmine
39
Use for INDIRECT-acting Cholinoceptor stimulants
Muscle relaxant reversal
40
Where do cholinesterase inhibitors bind to block enzyme's action?
anionic and esteric sites
41
In reference to ech-esterase enzyme site, where & how does Neostigmine, pyridostigmine, and edrophonium bind.
- Neostigmine & pyridostigmine covalently bind at esteratic site - Edrophonium hydrogen binds to anionic site
42
Which type INDIRECT-acting Cholinoceptor stimulant has irreversible inactivation? Why?
- Organophosphates form irreversible bond with enzyme to for an ineffective complex - can't be hydrolyzed - Reversal effects require new enzyme production
43
Myasthenia Gravis
- Affects skeletal muscle NMJ - Autoimmune process produces antibodies, which decrease functional nicotinic receptors on end plates. - Symptoms: weakness, and fatigue which improves with rest and worsens with exercise. Often difficulty w/ speaking, swallowing, breathing
44
Drug class that Myasthenia gravis (MG) patients are VERY sensitive to and why?
NDMRs (functional receptors are blocked)
45
Drugs used to treat MG, and why
- Cholinesterase inhibitors | - Increase Ach present, therefor increase stimulation to nicotinic receptors
46
MG crisis vs. Cholinergic crisis
- MG crisis: pt. weak because not enough drug/ ach present | - Cholinergic crisis: pt. weak because too much much drug / ach
47
How is MG vs. Cholinergic crisis differentiated to diagnose?
Tensilon Challenge
48
What is involved in a Tensilon Challenge
- Edrophonium is given. If pt. gets better, than MG crisis was the problem. (Ach levels were low...increased with drug..pt. feels better) - If pt. gets worst, than Cholinergic crisis is the problem (pt. has too much Ach r/ too much ach-esterase,causing increased levels makes pt. worst)
49
Neuromuscular blockade mechanisms
- Channel blockade (closed ion channel blockade: pre-syneptic block) (open ion channel blockade- Succinylcholine) - Receptor desensitization (mechanism unknown): agonist receptor binding, but no ion channel
50
Drug class and drug of Open ion channel Neuromuscular blockade mechanism
- NDMR | - Succinylcholine
51
How are esters absorbed...metabolized...and cleared in the body?
- Poorly absorbed r/t hydrophillic properties - Hepatic metabolism - Urinary Clearance
52
What inhibits the action of Ach
acetylcholinesterase
53
Effect of direct acting cholinoceptor stimulation vs. indirect acting.
Results/ effects are the same
54
Where do cholinesterase inhibitors bind to block enzyme's action
At the anionic and esteric sites
55
What is the difference between a Myasthenia Gravis Crisis and a Cholinergic crisis?
- Myasthenia G. crisis requires more drug (weakness from not enough cholinesterase inhibitor present) - Cholinergic crisis has too much drug present (weakness from depolarizing blockade from too much Ach present)
56
Define malignant Hyperthermia
an AUTOSOMAL DOMINANT inherited skeletal muscle disorder. Dx. by muscle biopsy. During a crisis Ca+ is greatly increased & there's a problem w/re-uptake d/t defective channel receptors leading to sustained muscle contractions> severe cellular O2 debt>demand for ATP>glycolysis>lactic acidosis>membrane instability>cellular rupture>rhabdomyolysis
57
What are the 2 NMBDs that undergo Hoffman's hydrolysis?
- Atracurium | - Cisatracurium
58
Ultra short acting NMBD
Succinylcholine
59
Short acting NMBD
Mivacurium (Mivacron)
60
Intermediate acting NMBD
- Veruronium (Norcuron) - Rocuronium (Zemuron) - Atricurium - Cisatricurium - DTC (Curare)
61
Long acting NMBD
-Pancuronium -Pipecuronium (-Gellamine)
62
Biisoquaternarty aminosteroid NMBD
- Pancuronium | - Pipecuronium
63
Isoquinolinium NMBD
DTC (Curare)
64
Benzisoquinolinium NMBD
- Mivacurium (Mivacron) - Atricurium (Tracurium) - Cisatracurium (Nimbex) - (Doxacurium)
65
Monoquaternary Aminosteroid NMBDs
- Vecuronium (Norcuron) | - Rocuronium (Zemron)
66
- NMBDs that you can give a priming dose. | - How much is the priming dose
Can give 10% priming dose with: - Cisatracurium (Nimbex) - Vecuronium (Norcuron) - Rocuronium (Zemron)
67
The 2 NMBDs whose hydrolysis can be affected by atypical pseudocholinesterase
- Succinylcholine | - Mivacurium (Mivacron)
68
NMBD used for rapid sequence intubation (RSI)
- Succinylcholine - Rocuronium (Vecuronium not really good for RSI r/t prolong onset)

Pharmacology Exam 3 (Toy's) (5 decks)

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