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Cholinergic Drugs Flashcards

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1
Q

2 types of Ach receptors

A

Muscarinic (heart, smooth muscles, exocrine glands)

Nicotinic (ganglion and skeletal muscles)

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2
Q

What do direct-acting cholinergic drugs affect?

A

Muscarinic and nicotinic receptors (direct binding)

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3
Q

What do indirect-acting cholinergic drugs affect?

A

Mainly acetylcholinesterase

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4
Q

Examples of direct-acting cholinergic drugs

A

Choline esters: acetylcholine, metacholine
Carbamoyl esters: carbachol, bethanechol
Natural alkaloids: pilocarpine, muscarine

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5
Q

Difference between tertiary and quaternary agents

A

Tertiary: Neutral, therefore lipid soluble, can pass BBB
Quaternary: (+) charge, water soluble, CANNOT cross BBB

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6
Q

Examples of tertiary agents

A

Alkaloids (pilocarpine), Physostigmine

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7
Q

Examples of quaternary agents

A

Choline esters, muscarine (??), simple alcohols (edrophonium), carbamates

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8
Q

2 divisions of direct-acting cholinomimetics

A

Choline esters and Alkaloids

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9
Q

Cholinomimetic choline ester groups

A

1) Acetic acid esters (Acetylcholine, methacholine)

2) Carbamic acid esters (carbachol, bethanechol)

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10
Q

Acetylcholine profile

A 
Susceptability to AchE: +++
Muscarinic action: +++
Nicotinic action: +++
Antagonized by atropine: +++
Does not cross BBB, very short half-life
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11
Q

Methacholine profile

A 
Susceptability to AchE: +
Muscarinic action: +++
Nicotinic action: +
Antagonized by atropine: +++
More resistant to hydrolysis
NO LONGER USED
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12
Q

Carbachol profile

A 
Susceptability to AchE: -
Muscarinic action: ++
Nicotinic action: +++
Antagonized by atropine: +
Mitotic drug for glaucoma
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13
Q

Bethanechol profile

A

Susceptability to AchE: -
Muscarinic action: +++
Nicotinic action: -
Antagonized by atropine: +++

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14
Q

The muscarinic receptor is highly stereoselective. Which isomer of bethanechol does it have more affinity?

A

S-bethanechol is 1000x more potent than R-bethanechol

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15
Q

Examples of natural cholinomimetic alkaloids

A 
Pilocarpine (tertiary)
Muscarine (quaternary)
Nicotine
Labeline (tertiary)
Arecholine
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16
Q

Which is the only cholinomimetic alkaloid with therapeutic use?

A

Pilocarpine

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17
Q

Examples of synthetic cholinomimetic alkaloids

A

dimethylphenylpiperazinium (DMPP)
Oxotremorine
**Both used for research

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18
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: CVS

A

Decrease HR = (-) chronotrophy
Decrease SA & AV node conduction = (-) dromotrophy
(-) ionotrophy
Generalized vasodilation (from NO formation in endothelial walls/blood vessels)
LARGE doses: depressed AV conduction

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19
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: GIT

A 
Stimulation of GI smooth muscles, tone and motility
Increased secretions
Relaxation of sphincters
=DIARRHEA!!!! cha cha cha!!! =D 
Hi baby!
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20
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: GUT

A

Contraction of detrussor muscle

Relaxation of trigone and external sphincter

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21
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: Respiratory system

A

Contraction of bronchial smooth muscles

Increased tracheobronchial secretions

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22
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: Eyes

A

Miosis - contraction of pupillary sphincter

Cyclospasm - contraction of ciliary muscles

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23
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: Exocrine glands

A

Increased secretions of ALL glands: lacrimal, salivary, eccrine, sweat, nasopharyngeal, gastric, intestinal

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24
Q

Pharmacologic muscarinic actions of cholinomimetic drugs: CNS

A

For tertiary only: tremors, hypothermia, locomotor activity, improved cognition

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25
Pharmacologic nicotinic actions of cholinomimetic drugs: NMJ
Disorganized fasiculations or strong contractions of the entire muscle "depolarization blockade" - stimulation and then flaccid paralysis d/t persistent depolarization at NMJ
26
Pharmacologic muscarinic actions of cholinomimetic drugs: CNS
High concentrations: emesis, tremor, stimulation of respiratory center Higher concentration: convulsions to coma
27
Pharmacologic muscarinic actions of cholinomimetic drugs: Autonomic ganglia
Will depend on the dominant division of that organ CVS: sympathiomimetic (hypertension, tachycardia, followed by bradycardia) GIT, GUT: parasympathetic (nausea, emesis, diarrhea, voiding of urine)
28
Pharmacologic muscarinic actions of cholinomimetic drugs: Adrenal medulla
Increase Epi and Norepi release | Plus Dopa, VIP, Ach
29
Clinical uses of cholinomimetic drugs: Opthalmology
Glaucoma (pilocarpine, carbachol) Iritis, keratitis Accomodative esotropia - strabismus, hyperemetropic accomodative error
30
Clinical uses of cholinomimetic drugs: GI d/o
``` To increase GI motility Postop gastric distention, gastric atony Congenital megacolon Ileus **Bethanechol ```
31
Clinical uses of cholinomimetic drugs: Xerostomia
In head and neck radiation Sjogren's syndrome **Pilocarpine, bethanechol, Cevimaline (new drug)
32
Clinical uses of cholinomimetic drugs: CNS
Dementia | **Taclifenasine, Xanomeline
33
Major Contraindications of cholinomimetic drugs
``` Asthma Hyperthyroidism Coronary insufficiency Acid Peptic disease GIT obstruction ```
34
Adverse effects of cholinomimetic drugs
``` Flushing Sweating Salivation Abdominal cramps Belching Sensation of tightness in urinary bladder Difficulty in visual accommodation Bronchospasm Hypotension Bradycardia ```
35
Cholinomimetic Poisoning and treatment
Exaggeration of parasympathetic effects Treat with competitive blockers: atropine Epinephrine Supportive therapy
36
Treatment of mushroom poisoning: Mycetism
Dependent on species | Fast, without delay
37
Mushroom species: Inocybe & Clitocybe
High muscarine concentration Symptoms in 30-60 mins Treatment: Atropine
38
Mushroom species: Amantia
Contains muscarine, muscimol, ibotenic acid, etc S/Sx: irritability, restlesness, ataxia, hallucination, delirium, drowsiness, sedation Treatment: Mainly supportive, Benzodiazapines (restlessness)
39
Mushroom species: Psilocybe & Panaeolus
Contains psitocybin and tryptamine derivatives | S/Sx: hallucinations
40
Mushroom species: Gyromitra
Toxic substance: acetylaldehyde methylformyl hydrazone | S/Sx: GI d/o, delayed hepatotoxicity
41
Mushroom species: Amantia phalloides, leptiota, galerina
Worst of all the mushrooms (50% of fatal cases) Toxic substance: Amatoxins S/Sx: diarrhea, abdominal cramps, symptom free for 24 hours, hepatic/renal malfunction Treatment: Supportive, penicillin, thioctic acid, silbinin
42
MOA of indirect acting cholinomimetics
Inhibit hydrolysis of Ach by Acetylcholinesterase (AchE)
43
What are the steps for degradation of Ach by AchE
1) Ach binds to active site of AchE 2) It is then hydrolyzed to yield free choline and the acetylated enzyme 3) The COVALENT acetyl bond is split by hydration * *All this in 150 microseconds
44
What does an indirect acting cholinomimetic do?
It attaches to AchE and is consequently hydrolysed = Ach is spared from being degraded
45
2 Types of Cholinesterases
Acetylcholinesterase (specific for Ach) | Pseudocholinesterase or Butyrylcholinesterase (non-selective)
46
Examples of reversible anti-cholinesterases
1) Non-covalent inhibitors: Edrophonium, Tacrine, donepezil | 2) Carbamate inhibitors
47
Examples of carbamate inhibitors
``` Tertiary: Physostigmine Quaternary: Pyridostigmine Neostigmine Rivastigmine Propoxur (Baygon) Ambenomium Benzpyrinium Demecarium Carbaryl Distigmine ```
48
What are the uses of Edophorium?
``` For diagnosis (not treatment!!!) of Myasthenia Gravis For differential diagnosis between Myasthenia crisis vs cholinergic crisis ```
49
Drugs used as anti-curare (for reversal of NM blockade: PANE
``` Mnemonic: PANE Pyridostigmine Ambenomium Neostigmine Edrophonium ```
50
In abdominal surgeries, PANE drugs are given with what anti-muscarinic drug and why is it given?
Atropine, to block muscarinic receptors while reversing the neuromuscular blockade
51
Use for Rivastigmine
Alzheimer's | **Cross BBB
52
Uses for Physostigmine (tertiary)
Atropine intoxication
53
Use for Neostigmine (quaternary)
Curare intoxication
54
Use for Pyridostigmine (quaternary)
Chronic management of Myasthenia gravis Stimulation of bladder and GIT Has direct action at nicotinic NMJ
55
Examples of irreversible anticholinesterases:
``` Organophosphates: Echothiophate (more stable than others) Malathion Parathion Fenthion Chloropyrifos Dimpylate Nerve gas: Sarin, soman, tabun, cyclosarin ```
56
What does aging involve? (in organophosphate poisoning)
Breaking of the oxygen-phosphorus bonds of the inhibitor which further strengthens the phosphorus enzyme bond
57
What are the 2 active sites of AchE and what part of Ach do they bind?
``` Anionic site (glutamate)- choline (basic) moiety Esteratic site (histidine & serine) ```
58
Which active site of AchE do organophosphates bind to? Is it reversible or irreversible?
Only to esteratic sites (via serine residues) | It is irreversible especially after aging
59
What is the management for organophosphate poisoning? When do they need to be given?
Enzyme regenerators: Pralidoxime Obidoxime Need to be given before aging
60
Examples of AchE inhibitors that bind to both active sites of AchE
Physostigmine | Neostigmine
61
Examples of AchE inhibitors that bind to anionic active site of AchE
Edrophorium
62
Examples of AchE inhibitors that bind to esteratic active site of AchE
Dyflos
63
What are the 3 steps to Ach degradation
1) Bind to enzyme via electrostatic bond 2) Initial hydrolysis: acetyl group transfer to serine group = acetylated enzyme + free choline 3) Spontaneous hydrolysis of acetylated enzyme
64
What is the MOA of cholinesterase reactivators
Breaks the phosphorus-enzyme bond formin a phosphoxime
65
Pharmacologic actions/effects of AchE inhibitors: Eyes
Miosis, contraction of ciliary muscles Decrease elevated IOP DRUGS: Physostigmine, Demecarium, Echothiophate
66
Pharmacologic actions/effects of AchE inhibitors: GIT and GUT
Increased GIT motility and secretions Increase contraction of detrusor muscle and relaxation of trigone and sphincter DRUG: Neostigmine
67
Pharmacologic actions/effects of AchE inhibitors: NMJ
Therapeutic conc: Moderately prolongs actions of released Ach Higher conc: fasiculations followed by flaccid paralysis "depolarization block"
68
Pharmacologic actions/effects of AchE inhibitors: CNS
Initial excitation followed by convulsions and coma and respiratory failure Can be antagonized by atropine DRUGS (Alzheimers): Donepezil, Rivastigmine, Galantamine
69
Pharmacologic actions/effects of AchE inhibitors: CVS
Effects of parasympathetic limb dominate Mimic vagal nerve activation of the heart Decreased BP, CO, HR Large, toxic doses: Marked decrease in HR, CO and BP
70
Adverse effects of Anticholinesterase drugs
``` Exaggerated Parasympathetic activity GI distress Salivation and sweating Bradycardia Bronchospasm Difficulty of visual accomodation Flushing ```
71
What is DUMBELS in organophosphate poisoning?
``` Diarrhea Urinary frequency Miosis and muscle weakness Bronchospasm, bradycardia Emesis, excitation Lacrimation Salivation, sweating, seizures ```
72
Therapeutic uses of AchE inhibitors: Opthalmology
Glaucoma: Acute angle closure Direct: Pilocarpine Indirect: Physostigmine, demecarium, echotiophate
73
Therapeutic uses of AchE inhibitors: NMJ
Myasthenia gravis (diagnosis (edrophonium) and treatment (pyridostigmine, neostigmine, ambenomium)) Curare or curare-like OD Adjunct to surgical anesthesia
74
Therapeutic uses of AchE inhibitors: GIT and GUT
``` Postop ileus Congenital megacolon Urinary retention DRUGS: bethanechol, neostigmine Xerostomia (pilocarpine, cevimaline) ```
75
Therapeutic uses of AchE inhibitors: Antimuscarinic drug intoxication
Physostigmine (only if necessary) of atropine poisoning
76
Therapeutic uses of AchE inhibitors: CNS
Alzheimer's DRUGS: Donepezil, Rivastigmine, Galantamine Note: Memantine (N-methyl-D-aspertate receptor inhibitor) is still the #1 drug used but it is NOT an anticholinesterase drug

Pharmacology (14 decks)

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