Cholinergic Agonists and Antagonists Flashcards

1
Q

What are the functions of the M1 muscarinic receptor?

A

Activates myenteric plexus

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2
Q

What are the functions of the M2 muscarinic receptor?

A

Decreases HR and contraction via opening of the K channels

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3
Q

What are the functions of the M3 muscarinic receptor?

A
Pupillary constriction
Bronchoconstriction
Increase GI motility
Contract bladder detrusor
Stimulate salivary secretion
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4
Q

What are the muscarinic receptors?

A

M1
M2
M3

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5
Q

What are the nicotinic receptors?

A

Nn

Nm

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6
Q

What is the Nn receptor?

A

Neuronal nicotinic receptor

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7
Q

What is the Nm receptor?

A

Muscle cell nicotinic receptor

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8
Q

What receptor does nicotine bind?

A

Nn

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9
Q

What is the effect of nicotine?

A

Diffuse activation of central and peripheral nicotinic receptors

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10
Q

Nicotine indication

A

Limited to preparations for smoking cessation often in a transdermal patch

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11
Q

Nicotine Toxicity

A

Effects include irritation at site of administration and dyspepsia

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12
Q

What does succinylcholine stimulate?

A

Succinylcholine sticks on the Nm receptor for a
long period of time and that leads to prevention
of action potential conduction by blocking the Nm receptor

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13
Q

Succinylcholine indication

A

Used clinically as a muscle relaxant during intubation or electro convulsive shock therapy

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14
Q

Succinylcholine Contraindications

A

Familial hyperthermia

Skeletal muscle myopathies

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15
Q

What are the types of muscarinic agonists?

A

Quaternary nitrogen analogs
Tertiary amine alkaloids
Synthetic analogs

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16
Q

What does ACh stimulate?

A

Binds to both nicotinic and muscarinic receptors of the autonomic nervous system, the CNS and the neuromuscular junction.

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17
Q

ACh indication

A

It is rapidly hydrolyzed by acetyl- and plasma cholinesterases. Therefore, it has no therapeutic use.

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18
Q

What does methacholine stimulate?

A

Primarily muscarinic effects on smooth muscle, glands and heart

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19
Q

Methacholine indication

A

Used to diagnose bronchial hyperactivity in patients suspected of having asthma

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20
Q

Methacholine Toxicity

A

Bronchiolar constriction

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21
Q

Methacholine Contraindications

A

Contraindicated in pts given β-blockers since antidote to overdose is β-agonist.

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22
Q

What does carbachol stimulate?

A

Muscarinic and nicotinic activity

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23
Q

Is carbochol easily hydrolyzed by AChE?

A

Resistant to hydrolysis by AchE

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24
Q

Carbachol indication

A

Miotic agent for ocular surgery and glaucoma

Used as an intraocular injection to reduce pressure after cataract surgery

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25
Q

Carbachol Toxicity

A

Side effects are related to excessive muscarinic and nicotinic receptor activation i.e., bronchoconstriction, reduced cardiac conduction

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26
Q

Bethanechol targets

A

Muscarinic selectivity

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27
Q

Bethanechol hydrolysis

A

It is resistant to hydrolysis by cholinesterases

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28
Q

What is the effect of bethanechol?

A

It has selective action on muscarinic receptors of GI tract and urinary bladder and minimizes the cardiac effects.

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29
Q

Bethanechol indication

A

Post-op urinary retention

Neurogenic bladder atony

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30
Q

Bethanechol Toxicity

A

Bradycardia

Bronchoconstriction

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31
Q

Bethanechol Contraindications

A

Asthma
Peptic ulcer
Bradycardia

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32
Q

What are the quaternary nitrogen analogs?

A

Methacholine
Carbachol
Bethanechol

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33
Q

Muscarine targets

A

Pure muscarinic activity

34
Q

Muscarine hydrolysis

A

Resistant to hydrolysis (no ester moiety)

35
Q

Muscarine indication

A

No therapeutic use

36
Q

What is muscarine poisoning treated with?

A

Muscarinic poisoning causes profound parasympathetic activation, and is treated with atropine, a muscarinic receptor antagonist

37
Q

Pilocarpine targets

A

Pure muscarinic activity

38
Q

Pilocarpine and BBB

A

Crosses the BBB and has CNS effects

39
Q

Pilocarpine indication

A

Dry mouth due to head and neck radiotherapy
Sjogren’s syndrome
Open angle glaucoma
Acute and chronic angle-closure glaucoma

40
Q

Pilocarpine Toxicity

A

Excess muscarnic activation (slowed AV conduction), Hypotension
Excessive salivation
Bronchoconstriction

41
Q

Pilocarpine Contraindications

A

Administer with care to patients taking β-blockers due to exacerbation of conduction slowing.

42
Q

Acetylcholinesterase

A

Acetylcholinesterase catalyzes the hydrolysis of acetylcholine

43
Q

What are indirect cholinergic agonists?

A

Inhibition of cholinesterase protects acetylcholine from hydrolysis, and leads to the accumulation of endogenous acetylcholine and increased cholinergic activity. Thus, cholinesterase inhibitors act indirectly as cholinergic agonists.

44
Q

What is regional function of acetylcholinesterase?

A

Hydrolysis of acetylcholine liberated in synaptic cleft or in neuroeffector transmission.

45
Q

What is the regional function of butyl cholinesterase?

A

Plasma, non-specific esterase. Does hydrolyze certain exogenous drugs, e.g., succinylcholine.

46
Q

Neostigmine and BBB

A

Contains a quaternary nitrogen, and thus poorly penetrates blood brain barrier.

47
Q

What is the effect of neostigmine?

A

Inhibits acetylcholinesterase and has direct stimulatory effect on nicotinic receptors at the skeletal muscle endplate

48
Q

Neostigmine indication

A

Myasthenia gravis

Used to reverse neuromuscular blockade

49
Q

Neostigmine Toxicity

A

Side effects due to excessive Ach action at peripheral muscarinic and nicotinic receptors

50
Q

Neostigmine Contraindications

A

Intestinal obstruction

51
Q

Edrophonium targets

A

Inhibits cholinesterases and stimulates nicotinic receptors

52
Q

Edrophonium onset and duration of effect

A

Has a very rapid onset of action, and a very short duration of action (10-15 min)

53
Q

Edrophonium indication

A

Diagnosis of myasthenia gravis

Differential diagnosis of too little or too much AchE inhibitor in myasthenia gravis

54
Q

Edrophonium Toxicity

A

Bradycardia

55
Q

Edrophonium Contraindications

A

Intestinal blockade

Urinary obstruction

56
Q

How does treatment with edrophonium allow for differential diagnosis in myasthenia gravis?

A

Treatment with short acting cholinesterase inhibitor reduces symptoms if muscle weakness is due to disease progression. It will worsen symptoms if due to cholinesterase toxicity.

57
Q

Physostigmine and BBB

A

Readily crosses the BBB

58
Q

Physostigmine onset and duration

A

Inactivated by plasma cholinesterases but takes a long time with duration of action up to 2 hours

59
Q

Physostigmine indication

A

Antidote for muscarinic antagonist poisoning

60
Q

Physostigmine Toxicity

A

Side effects related to increased Ach
at muscarinic or nicotinic receptors.

Convulsions, respiratory and CV depression

61
Q

Physostigmine Contraindications

A

Asthma
Cardiac insufficiency
Gut obstruction

62
Q

Donezipil indication

A

Alzheimer’s Disease

63
Q

Donezipil target

A

Inhibits only acetylcholinesterase and is reversible inhibitor in the CNS

64
Q

What are the irreversible cholinesterase inhibitors?

A

Organophosphates phosphorylate cholinesterases which exhibits severe toxicity.

65
Q

What are the signs of organophosphate toxicity?

DUMBBELS

A
D Diarrhea
U Urination
M miosis
B bradycardia 
B bronchorrea 
E emesis
L lacrimation 
S Salivation
66
Q

How is atropine used in the treatment of organophosphates?

A

It protects from systemic muscarinic effects

67
Q

How does pralidoximine treat organophosphate poisoning?

A

Reactivation of the alkylphosphorylated acetylcholinesterase with Pralidoxime Chloride (2-PAM)

68
Q

Echothiophate targets

A

Irreversible acetycholinesterase inhibitor

69
Q

Echothiophate indication

A

Produce long term miosis in the treatment of open angle

glaucoma

70
Q

Echothiophate Toxicity

A

Blurred vision

Brow ache

71
Q

Echothiophate duration

A

Long half life and once a day administration is enough

72
Q

What are the competitive muscarinic antagonists?

A

Atropine
Scopolamine
Glycopyrrolate

73
Q

Atropine target

A

Muscarinic antagonist

74
Q

Atropine indication

A

Organophosphate poisoning
Induction of mydriasis and cycloplegia (though long duration of action)
Reverse bradycardia of vagal origin
Reverse gastrointestinal hypermotility
Bladder spasms (urgency) associated with cystitis

75
Q

Scopolamine target

A

Muscarinic antagonist

76
Q

Scopolamine indication

A

Used in preparation for surgical anesthesia to minimize
secretion

To treat nausea and vomiting associated with motion sickness and chemotherapy induced nausea

77
Q

Scopolamine Toxicity

A

Anti-muscarinic actions

78
Q

Scopolamine Contraindications

A

Narrow angle glaucoma

79
Q

Glycopyrrolate target

A

Muscarinic antagonist

80
Q

Glycopyrrolate indication

A

Its antimuscarinic activity is used to prevent overstimulation of the gut during reversal of neuromuscular blockade

81
Q

Glycopyrrolate Toxicity

A

Heat stroke due to inability to sweat in heat

82
Q

What are the signs of atropine poisoning?

A
Dry mouth
Hot
Dilated pupils
Tachycardia
Increased BP
Nervousness