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PT 1 > L16 Cholinergic Agonists and Antagonists > Flashcards

L16 Cholinergic Agonists and Antagonists Flashcards

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
Q

What is the mechanism of action of carbachol?

A

Muscarinic and nicotinic activity

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26
Q

Describe the effect of acetylcholinesterase on carbachol.

A

Less effective, as carbachol is more resistant to hydrolysis by acetylcholinesterase

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27
Q

What are the indications of carbachol?

A
  1. Miotic agent (ocular surgery and glaucoma)*
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28
Q

What are the toxicities of carbachol?

A
  1. Excessive muscarinic activation (bronchoconstriction, reduced cardiac conduction)*
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29
Q

What is the mechanism of action of bethanechol?

A

Muscarinic receptor activity of GI tract and urinary bladder (no nicotinic)

30
Q

Describe the effect of acetylcholinesterase on bethanechol.

A

Resistant to hydrolysis by cholinesterases

31
Q

What are the indications of bethanechol?

A
  1. Post-operative non-obstructive urinary retention*

2. Neurogenic bladder atony*

32
Q

What are the toxicities of bethanechol?

A
  1. Bradycardia* (though less so, as there is less activity at M2 receptors)
  2. Bronchoconstriction*
33
Q

What are the contraindications of bethanechol?

A
  1. Asthma*
  2. Peptic ulcer*
  3. Bradycardia*
34
Q

What are the naturally occurring tertiary amines?

A
  1. Muscarine

2. Pilocarpine

35
Q

Muscarine has no clinical use; however, it causes poisoning and must be treated with ___.

A

Atropine

36
Q

What is the mechanism of action of pilocarpine?

A

Pure muscarinic receptor agonist that crosses the BBB

37
Q

What are the indications of pilocarpine?

A
  1. Dry mouth due to head and neck radiotherapy or Sjogren’s syndrome*
  2. Open angle and angle-closure glaucoma*
38
Q

What are the toxicities of pilocarpine?

A
  1. Excess muscarinic activation
  2. Hypotension
  3. Excessive salivation
  4. Bronchoconstriction
39
Q

What does aceylcholinesterase do?

A

Catalyzes the hydrolysis of ACh to choline and acetic acid

40
Q

What does a cholinesterase inhibitor do?

A

Increase endogenous ACh and cholinergic activity

41
Q

What are the two types of endogenous cholinesterases?

A
  1. Acetylcholinesterase

2. Butyrylcholinesterase

42
Q

What is the function of acetylcholinesterase?

A

Hydrolysis of ACh liberated in the synaptic cleft or in neuroeffector transmission

43
Q

What are the reversible cholinesterase inhibitors?

A
  1. Neostigmine
  2. Edrophonium
  3. Physostigmine
  4. Donepezil
44
Q

What is the mechanism of action of neostigmine?

A

Inhibits AchE, leading to direct stimulatory effects on nicotinic receptors at the skeletal muscle endplate

45
Q

What are the indications of neostigmine?

A
  1. Myasthenia gravis*

2. Reversal of non-depolarizing neuromuscular blockade*

46
Q

What are the toxicities of neostigmine?

A
  1. Muscarinic and nicotinic excess*
47
Q

What are the contraindications of neostigmine?

A
  1. Intestinal obstruction
48
Q

Does neostigmine penetrate the BBB?

A

No

49
Q

What is the mechanism of action of edrophonium?

A

Inhibits cholinesterases and stimulates nicotinic receptors at the NMJ

50
Q

Describe the onset and duration of action of edrophonium.

A

Rapid onset, short duration of action

51
Q

What are the indications of edrophonium?

A
  1. Diagnosis of myasthenia gravis*
  2. Differential diagnosis between progression of myasthenic weakness and a cholinergic crisis due to cholinesterase toxicity*
52
Q

What are the toxicities of edrophonium?

A
  1. Bradycardia*

2. Cardiac standstill

53
Q

What are the contraindications of edrophonium?

A
  1. Intestinal blockade

2. Urinary obstruction

54
Q

Does physostigmine cross the BBB?

A

Yes

55
Q

What are the indications of physostigmine?

A
  1. Antidote for muscarinic antagonist poisoning (delirium)*
56
Q

What are the toxicities of physostigmine?

A
  1. Excess muscarinic and nicotinic receptor activation (convulsions, respiratory/CV depression)*
57
Q

What are the contraindications of physostigmine?

A
  1. Asthma
  2. Cardiac insufficiency
  3. Intestinal obstruction
58
Q

What is the mechanism of action of donepezil?

A

Reversible inhibitor of acetylcholinesterase in the CNS

59
Q

What are the indications of donepezil?

A
  1. Alzheimer’s disease*
60
Q

What are the irreversible cholinesterase inhibitors?

A
  1. Organophosphates (used as insecticides)

2. Nerve gases

61
Q

What are the symptoms of anticholinesterase poisoning?

A
  1. Diarrhea
  2. Urination
  3. Miosis
  4. Bradycardia
  5. Bronchorrea
  6. Emesis
  7. Lacrimation
  8. Salivation
    DUMBBELS
62
Q

What are the 4 major methods of treating anticholinesterase poisoning?

A
  1. Ventilation
  2. Suction of tracheal secretions
  3. Anti-muscarinic agent (atropine)
  4. Reactivation of acetylcholinesterase with Pralidoxime Chloride (2-PAM)
63
Q

What is the mechanism of action of echothiophate?

A

Irreversible acetylcholinesterase inhibitor

64
Q

What are the indications of echothiophate?

A
  1. Long-term miosis in the treatment of open angle glaucoma*
65
Q

What are the muscarinic antagonists?

A
  1. Atropine
  2. Scopolamine
  3. Glycopyrrolate
66
Q

What are the indications of atropine?

A
  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
Q

What are the indications of scopolamine?

A
  1. Nausea and vomiting associated with motion sickness or chemo*
68
Q

What are the toxicities of scopolamine?

A
  1. Anti-muscarinic actions*
69
Q

What are the indications of glycopyrrolate?

A
  1. Protect against excessive muscarinic effects of cholinesterase inhibitors during reversal of neuromuscular blockade*
70
Q

What are the toxicities of glycopyrrolate?

A
  1. Can cause heat stroke due to inability to sweat in heat
71
Q

Describe atropine poisoning.

A 
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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