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PT 1 > L16 Cholinergic Agonists and Antagonists > Flashcards

L16 Cholinergic Agonists and Antagonists Flashcards

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1
Q

What is the endogenous agonist of cholinergic receptors?

A

Acetylcholine

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2
Q

What are the two classes of cholinergic receptors?

A
  1. Muscarinic receptors (G-protein linked)

2. Nicotinic (ligand-gated ion channels)

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3
Q

Where are muscarinic receptors located?

A
  1. Nerves
  2. Heart and smooth muscle
  3. Glands and endothelium
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4
Q

Where are nicotinic receptors located?

A
  1. Neuromuscular end plate, skeletal muscle

2. Autonomic ganglion cells

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5
Q

What does M1 do?

A

Activates the myenteric plexus

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6
Q

What does M2 do?

A

Decreases HR and contraction

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7
Q

Where on the heart are M2 receptors located?

A

SA node

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8
Q

What does M3 do?

A

Contracts ciliary muscle, bronchiolar muscle, GI smooth muscle, and bladder detrusor muscle

Stimulates secretions of the GI tract and glands

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9
Q

What are the two types of nicotinic receptors?

A

Nm (skeletal muscle membranes)

Nn (plasma membranes of parasympathetic and sympathetic post-ganglionic cells in the autonomic ganglion)

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10
Q

Describe the structure of nicotinic receptors.

A

Pentameric transmembrane polypeptides that forma cation-selective channel permeable to K+ and Na+

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11
Q

Nicotinic agonists can activate both the sympathetic and parasympathetic systems simultaneously - why?

A

Because nicotinic receptors are present on post-ganglionic cells of both systems

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12
Q

What are the two major nicotinic receptor agonists?

A
  1. Nicotine

2. Succinylcholine

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13
Q

Where does nicotine act?

A

Nn receptors in autonomic ganglia and CNS

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14
Q

What is nicotine used for clinically?

A

Smoking cessation

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15
Q

Where does succinylcholine act?

A

Blocks nicotinic receptors at the NMJ

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16
Q

What are the two broad categories of muscarinic agonists?

A
  1. Quaternary nitrogen analogs

2. Naturally occurring tertiary amine alkaloids and synthetic analogs

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17
Q

What are the 4 quaternary nitrogen analogs?

A
  1. Acetylcholine
  2. Methacholine
  3. Carbachol
  4. Bethanechol
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18
Q

What does acetylcholine bind to?

A

Nicotinic and muscarinic receptors

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19
Q

Why does acetylcholine have no therapeutic use?

A

It is rapidly hydrolyzed by acetyl- and plasma cholinesterases.

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20
Q

Why is methacholine clinically useful?

A

Though it is hydrolyzed by acetylcholinesterase, hydrolysis is slower, so it has a longer duration of action.

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21
Q

What is the mechanism of action of methacholine?

A

Primarily muscarinic effects on smooth muscle, glands, and the heart; limited nicotinic effects

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22
Q

What are the indications of methacholine?

A
  1. Diagnosis of asthma*
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23
Q

What are the toxicities of methacholine?

A
  1. Bronchiolar constriction*
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24
Q

What are the contraindications of methacholine?

A
  1. Patients taking beta-blockers*
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25
What is the mechanism of action of carbachol?
Muscarinic and nicotinic activity
26
Describe the effect of acetylcholinesterase on carbachol.
Less effective, as carbachol is more resistant to hydrolysis by acetylcholinesterase
27
What are the indications of carbachol?
1. Miotic agent (ocular surgery and glaucoma)*
28
What are the toxicities of carbachol?
1. Excessive muscarinic activation (bronchoconstriction, reduced cardiac conduction)*
29
What is the mechanism of action of bethanechol?
Muscarinic receptor activity of GI tract and urinary bladder (no nicotinic)
30
Describe the effect of acetylcholinesterase on bethanechol.
Resistant to hydrolysis by cholinesterases
31
What are the indications of bethanechol?
1. Post-operative non-obstructive urinary retention* | 2. Neurogenic bladder atony*
32
What are the toxicities of bethanechol?
1. Bradycardia* (though less so, as there is less activity at M2 receptors) 2. Bronchoconstriction*
33
What are the contraindications of bethanechol?
1. Asthma* 2. Peptic ulcer* 3. Bradycardia*
34
What are the naturally occurring tertiary amines?
1. Muscarine | 2. Pilocarpine
35
Muscarine has no clinical use; however, it causes poisoning and must be treated with ___.
Atropine
36
What is the mechanism of action of pilocarpine?
Pure muscarinic receptor agonist that crosses the BBB
37
What are the indications of pilocarpine?
1. Dry mouth due to head and neck radiotherapy or Sjogren's syndrome* 2. Open angle and angle-closure glaucoma*
38
What are the toxicities of pilocarpine?
1. Excess muscarinic activation 2. Hypotension 3. Excessive salivation 4. Bronchoconstriction
39
What does aceylcholinesterase do?
Catalyzes the hydrolysis of ACh to choline and acetic acid
40
What does a cholinesterase inhibitor do?
Increase endogenous ACh and cholinergic activity
41
What are the two types of endogenous cholinesterases?
1. Acetylcholinesterase | 2. Butyrylcholinesterase
42
What is the function of acetylcholinesterase?
Hydrolysis of ACh liberated in the synaptic cleft or in neuroeffector transmission
43
What are the reversible cholinesterase inhibitors?
1. Neostigmine 2. Edrophonium 3. Physostigmine 4. Donepezil
44
What is the mechanism of action of neostigmine?
Inhibits AchE, leading to direct stimulatory effects on nicotinic receptors at the skeletal muscle endplate
45
What are the indications of neostigmine?
1. Myasthenia gravis* | 2. Reversal of non-depolarizing neuromuscular blockade*
46
What are the toxicities of neostigmine?
1. Muscarinic and nicotinic excess*
47
What are the contraindications of neostigmine?
1. Intestinal obstruction
48
Does neostigmine penetrate the BBB?
No
49
What is the mechanism of action of edrophonium?
Inhibits cholinesterases and stimulates nicotinic receptors at the NMJ
50
Describe the onset and duration of action of edrophonium.
Rapid onset, short duration of action
51
What are the indications of edrophonium?
1. Diagnosis of myasthenia gravis* 2. Differential diagnosis between progression of myasthenic weakness and a cholinergic crisis due to cholinesterase toxicity*
52
What are the toxicities of edrophonium?
1. Bradycardia* | 2. Cardiac standstill
53
What are the contraindications of edrophonium?
1. Intestinal blockade | 2. Urinary obstruction
54
Does physostigmine cross the BBB?
Yes
55
What are the indications of physostigmine?
1. Antidote for muscarinic antagonist poisoning (delirium)*
56
What are the toxicities of physostigmine?
1. Excess muscarinic and nicotinic receptor activation (convulsions, respiratory/CV depression)*
57
What are the contraindications of physostigmine?
1. Asthma 2. Cardiac insufficiency 3. Intestinal obstruction
58
What is the mechanism of action of donepezil?
Reversible inhibitor of acetylcholinesterase in the CNS
59
What are the indications of donepezil?
1. Alzheimer's disease*
60
What are the irreversible cholinesterase inhibitors?
1. Organophosphates (used as insecticides) | 2. Nerve gases
61
What are the symptoms of anticholinesterase poisoning?
1. Diarrhea 2. Urination 3. Miosis 4. Bradycardia 5. Bronchorrea 6. Emesis 7. Lacrimation 8. Salivation DUMBBELS
62
What are the 4 major methods of treating anticholinesterase poisoning?
1. Ventilation 2. Suction of tracheal secretions 3. Anti-muscarinic agent (atropine) 4. Reactivation of acetylcholinesterase with Pralidoxime Chloride (2-PAM)
63
What is the mechanism of action of echothiophate?
Irreversible acetylcholinesterase inhibitor
64
What are the indications of echothiophate?
1. Long-term miosis in the treatment of open angle glaucoma*
65
What are the muscarinic antagonists?
1. Atropine 2. Scopolamine 3. Glycopyrrolate
66
What are the indications of atropine?
1. Organophosphate poisoning* 2. Induction of mydriasis and cycloplegia* 3. Reverse bradycardia of vagal origin* 4. Reverse GI hypermotility* 5. Bladder spasms associated with cytstitis*
67
What are the indications of scopolamine?
1. Nausea and vomiting associated with motion sickness or chemo*
68
What are the toxicities of scopolamine?
1. Anti-muscarinic actions*
69
What are the indications of glycopyrrolate?
1. Protect against excessive muscarinic effects of cholinesterase inhibitors during reversal of neuromuscular blockade*
70
What are the toxicities of glycopyrrolate?
1. Can cause heat stroke due to inability to sweat in heat
71
Describe atropine poisoning.
``` Blind as a bat Mad as a hatter Red as a beet Hot as a hare Dry as a bone Bowel and bladder lose their tone Heart runs alone ```

PT 1 (34 decks)

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