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Pharmacology > Cholinergic Agonists and Antagonists > Flashcards

Cholinergic Agonists and Antagonists Flashcards

1
Q

Cholinergic Agonists

  • Direct Acting
  • 1-Muscurinic receptor
  • 2-Nicotinic receptor
  • 3 Indirect Acting
  • Cholinergic Antagonist
  • 4-Muscurinic receptor antagonist
  • -Nicotinic receptor antagonists
  • -5-Ganglion blockers
  • -6-Neuromuscular blockers
    • Drugs that act presynaptically
  • -7-Inhibitors of ACh Synthesis
  • -8-Inhibitors of ACh Storage
  • -9-Inhibitors of ACh Release
A

-1-Acetylcholine, Bethanechol, Carbachol, Methacholine, Muscarine, Arecoline, Pilocarpine
-2-Nicotine
-3 Edrophonium, Carbamates (Physostigmine, Neostigmine, Pyridostigmeni), Organophosphates (Echothiophate, Malathion and Parathion), Nerve Agents (Tabun, Sarin, Soman), Tacrine/Donepezil/rivastigmine/galantamine all for Alzheimers. Pralidoxime to reactivate inhibited acetylcholinesterase before ageing occurs
*4-Atropine, Scopolamine, Synthetic (Ipratropium, Tiotropium, Homatropine, Cyclopentolate and Tropicamide, Benztropine, Trihexyphenidyl, Glycopyrrolate, Tolterodine)
*5- hexamethonium, mecamylamine, trimethaphan
*-6- Tubocurarine (nondepolarizing), Succynilcholine (depolarizing)
7-hemicholinium-3
8-Vesamicol
9-Botulinum Toxin

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2
Q

ACh has 4 primary direct effects on the cardiovascular system

A
  1. Vasodilation M3
  2. Decrease Heart Rate M2
  3. Decrease in rate of conduction M2
  4. Decrease in force of contraction M2
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3
Q

Small Dose ACh vs Large Dose ACh

A

Small=vasodilation=decrease in BP and reflex tachycardia

Large=bradycardia, and decrease in conduction and decrease in BP

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4
Q

ACh effects on various organ systems

A

Vasculature: vasodilation, release of NO
Eye iris: contraction and miosis
Ciliary muscles: contraction to accommodate to near vision
Salivary and lacrimal: increased secretion
Bronchi: Bronchoconstriction, increased secretions
GI: increased tone, peristaltic activity, secretions, relaxation of sphincters
Bladder: contraction of detrusor muscle, relaxation of sphincter
Sweat glands: diaphoresis
Male repro: Erection
Uterus: variable

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5
Q

Acetylcholine

A

*no therapeutic application because it affects too much and is quickly hydrolyzed by acetylcholinesterase and a little bit by butyrylcholinesterase.
Binds to Nicotinic and muscurinic receptors
Only real use is to get rapid miosis after delivery of lens in cataracts surgery

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6
Q

Bethanechol

A

Not hydrolyzed by acetylcholinesterase. Inactivated through hydrolysis by other esterases.
Strong Muscurinic action, no nicotinic
Treatment for a “lazy” bladder.

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7
Q

Carbachol

A

Both muscarinic and nicotinic agonist.
Not hydrolyzed by acetylcholinesterase.
Used for quick miosis during surgery, and reduces intraocular pressure after cataracts surgery

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8
Q

Methacholine

A

Mostly Muscarinic
Hydrolyzed slowly by AChesterase (almost totally resistant to hydrolysis by nonspecific cholinesterase)
Used for diagnosis of bronchial airway hyperreactivity in subjects that don’t clinical show asthma

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9
Q

Pilocarpine
Muscarine
Arecoline

A

P: tertiary amine, partial muscarinic agonist. Uses: Treat Glaucoma. Stimulate Sweating and salivation
M: acts almost exclusively at muscarinic receptors, not clinically used
A: act at both muscarinic and nicotinic receptors, not clinically used.

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10
Q

Nicotine

A

Tertiary amine, low doses causes ganglionic stimulation by depolarization affecting both SNS and PSNS at same time.
In CVS: increases heart rate and blood pressure
In GI: mainly PSNS, nausea, vomiting, diarrhea, voiding of bladder.
Increase in salivary and bronchial secretions.
At High doses, it causes a ganglionic blockade as a consequence of depolarization. Also causes a neuromuscular blockade.
- Nicotine is highly liposoluble
and absorbs fast via oral mucosa, lungs, GI, Skin and crosses the placenta and is secreted in milk.
USE FOR QUITTING SMOKING

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11
Q

Indirect acting cholinergic agonists

A

These are cholinesterase inhibitors. They allow endogenous acetylcholine to remain in the synapse

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12
Q

Edrophonium

A

Binds reversibly. Effects last 2-10 minutes. Quaternary ammonium.
USES: diagnose myasthenia gravis becuase of its short acting duration. Used to reverse neuromuscular block produced by nondepolarizing muscular blockers

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13
Q

Carbamates

A

form covalent bond with enzyme but can spontaneously hydrolyze within 30 min - 6 hours

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14
Q

Organophosphates

A

They phosphorylate active sites of the enzyme and this is an extremely strong bond. It may undergo ageing which further strengthens the phosporous enzyme bond. ***Pralidoxine can reverse the bond but only before ageing occurs

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15
Q

Physostigmine

A

a carbamate, tertiary amine, treatment for overdoses of anticholinergic drugs like atropine. **Do NOT give PHyso to anyone on TCA because it will slow the heart conduction too much.
Adverse Effects: may lead to convulsions at high doses, bradycardia may occur, paralysis of muscles since ACh builds up at NMJ

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16
Q

Neostigmine

A

carbamate, Quaternary amine, reversal of nondepolarizing neuromuscular blockers after surgery. Used for symptomatic treatment of myasthenia grravis. Prevention and treatment of postoperative distention and urinary retention
Adverse: Salivation, flushing, low BP, Nausea, Abdominal Pain, diarrhea, bronchospasm

17
Q

Pyridostigmine

A

Carbamate, quaternary amine, treatment use for myasthenia gravis. *Most common anticholinesterase used for this

18
Q

Echothiophate

A

organoP. used for chronic open angle glaucoma, subacute or chronic angle closure glaucoma after iridectomy or where surgery is refused or contraindicated

19
Q

Malathion and Parathion

A

M: rapidly metabolized to inactive products in birds and mammals but not insects. safe enough to sell to the public
Parathion: not detoxified effectively in vertebrates so more dangerous. High yield in farmers

20
Q

Tabun, sarin, soman

A

very potent synthetic toxic agents

21
Q

Tacrine, Donepezil, rivistigmine, galantamine

A

active inhibitors of acetylcholinesterase for treatment of Alzheimers

22
Q

Atropine

A

binds competitively to muscarinic receptors. Tertiary amine
Mydriasis, unresponsive to light, cycloplegia (paralyisis of ciliary muscles so you can’t accomadate to near vision), antispasmodic in GI, Decreased gastric motility but HCl secretion not affected, decreased hypermobility of bladder, you block M2 on the heart causing tachycardia, secretions are inhibited for saliva, sweat, and tears.
t0.5=4hrs, eliminated in urine and metabolized in liver.
USES: reduce airway secretions for surgery, to increase heart rate or decrease AV vlock, antidoite to overdose on cholinergic drugs, antidote to mushroom poisoning, alleviates muscarinic side effects of anticholinesterase drugs like neostigmine

23
Q

Scopolamine

A

produces peripheral effects similar to atropine. Greater actions on CNS and longer duration. One of most effective drugs for motion sickness. Unusual effect: blocks short term memory, produces sedation unlike atropine. At high doses can cause excitation.
USES: for mydriasis and cyclopegia in diagnostic procedures, prevention of nausea

24
Q

Ipratropium and Tiotropium

A

inhalation drugs that treat COPD and Asthma

muscarinic antagonists

25
Q

Homatropine, cyclopentolate and tropicamide

A

tertiary amine, muscarinic antagonist.

-mydriasis with cycloplegia. Preferred to atropine because of its shorter duration of action.

26
Q

Benztropine and Trihexyphenidyl

A

tertiary amine used to treat parkinsons and extrapyramidal effects of antipsychotic drugs
muscarinic antagonist

27
Q

Glycopyrrolate

A

4 amine, used orally to inhibit the GI motility. Also prevents bradycardia during surgical procedures

28
Q

Tolterodine

A

3 amine for overactive bladder

29
Q

Contraindications for antimuscarinic drugs

A
  • angle-closure glaucoma
  • prostatic hypertrophy (you already have a hard enough time peeing
  • Elderly patients
30
Q

Hexamethonium, mecamylamine and trimethaphan

A

Ganglion blockers ti treat HTN. but they have a wide array of adverse effects and have been replaced by better drugs

31
Q

Tubocurarine

A

Non depolarizing competative neuromuscular blocker.
-bind to nicotinic receptor and prevent acetylcholine binding so no contraction. used to treat overdose with neostigmine or edrophonium
-Used in surgery to relax the body muscles.
-must give IV b/c oral absorption is too little
Side effects: may cause histamine release and moderately inhibit muscarinic receptors

32
Q

Succinylcholine

A

acts like ACh to cause depolarization through nicotinic receptor. It isn’t metabolized as effectively and so depolarization stays longer..
-Uses: useful when rapid endotracheal intubation is needed and also during ECT.
-Given by IV, very fast effect and quickly action 5-10 minutes
ADVERSE: malignant hyperthermia because there will be a flood of Ca from the SR. Dantrolene can block ca form leaving SR to reduce heat production and relaxing muscle tone.

33
Q

Hemicholinium 3

A

Inhibitor of ACh synthesis because it blocks high affinity transporter for choline. *Just a research tool

34
Q

Vesamicol

A

Inhibitor of ACh Storage

Blocks H+ACh antiporter to prevent storage. Also only a research tool

35
Q

Botulinum Toxin

A

Inhibitor of ACh Release

  • produced by C botulinum, prevent synaptic vesicle fusion.
  • Injected into muscles to treat torticollis, achalasia, strabismus, blepharospasm, and other focal dystonias
  • Approved to use for botox and can treat headache and pain syndromes
36
Q

Effects of Autonimic Ganglion Blockade

A

Arterioles, veins = Sympathetic adrenergic: vasodilation and decreased BP
Sweat Glands: Sympathetic cholinergic: anhydrosis
Everything else is Parasympathetic cholinergic
- Heart: tachycardia
-Iris: Mydriasis
-Ciliary Muscles: Cyclopegia: can’t focus near
-GI tract: reduced tone and motility
Urinary: urinary retention
Salivary Glands: xerostomia

Pharmacology (9 decks)

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