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RCS > Cholinergic Agonist and Antagonist > Flashcards

Cholinergic Agonist and Antagonist Flashcards

1
Q

What are the 4 primary direct effects ACh has on the cardiovascular system?

A
  1. Vasodilation (M3 effect)
  2. Decrease in cardiac rate (M2 effect)
  3. Decrease in rate of conduction in the SA and AV nodes (M2)
  4. Decrease in force of contraction (M2 effect)
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2
Q

What is the effect of IV infection of small dose of aceytlcholine?

A
  • Vasodilation mediated by activation of endothelial M3 receptors
  • Reflex tachycardia
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3
Q

What are the effects of a large dose of IV ACh?

A
  • Vasodilation
  • Bradycardia from enough ACh to overcome baroreceptor reflex by decrease conduction velocity through the AV node (M2 mediated)
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4
Q

What is the function of M3 receptors on endothelial cells?

A
  • relaxation of vascular muscle via relase of NO from endothelial cells
  • M3 muscarinic receptors on endothial cells are unninervated
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5
Q

What are the effects of Acetylcholine on vasculature (endothelial cells), eye iris, ciliary muscle, salivary/lacrimal glands, bronchi, heart, GI tract, urinary bladder, sweat glands, male reproductive tract, and uterus?

A
  • Vasculature (endothelial cells): relase of NO and vasodilation (decrease in BP)
  • Eye iris: contraction and miosis
  • Ciliary muscle: contraction and accomodation of lens to near vision
  • Salivary/lacrimal glands: watery secretions
  • Bronchi: constrictions, increase secretions
  • GI tract: increase tone, increase peristaltic activity, increase secretions, relaxation of sphincters
  • Urinary bladder: contraction of detrusor muscle, relaxation of sphincter
  • Sweat glands: diaphoresis
  • Male reproductive tract: erection
  • Uterus: variable
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6
Q

What are the two types of direct-acting cholinergic agonist chemical structure?

A

Esters of choline and naturally occuring alkaloids

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7
Q

What are the Choline Esters?

A
  1. Acetylcholine
  2. Methacholine
  3. Carbachol
  4. Bethanechol
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8
Q

Acetylcholine

A

M: muscarinic and nicotinic agoinst; rapidly hydrolysis by acetylcholinesterase and plasma butyrylcholinesterase

CA: to obtain rapid miosis during eye surgery

AE:

TCo: Half life too short, not used clinically

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9
Q

Bethanechol

A

M: strong muscarinic agonist, little/no nicotinic actions

CA: treatment of acute p/o and postpartum non obstructive (functional) unrinary retention, and for neurogenic atony of the urinary bladder with retention

AE: generalized cholinergic stimulation: sweating, salivation, flushing, low BP, nausea, abd pain, diarrhea, bronchospasm

TCo: almost completely selective for muscarinic receptors

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10
Q

Carbachol

A

M: muscarininc and nicotinic agonist

CA: obtaining miosis during surgery, reduce intraocular pressure after cataract surgery

AE:

TCo: poor hydrolysis by acetylcholinesterase

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11
Q

Methacholine

A

M: predominantly muscarinic agonist

CA: methacholine challenge test (diagnosis of bronchial airway hyperreactivity)

AE:

TCo: slower hydrolysis by acetylcholinesterase

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12
Q

What are the natural alkaloids?

A

Pilocarpine and Nicotine

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13
Q

Pilocarpine

A

M: partial muscarinic agonist (tertiary amine)

CA: management and second line agent for open angle glaucoma; treatment of symptoms of dry mouth and salivary mouth hypofunction caused by radiotherapy and Sjogren’s Syndrome

AE: can enter CNS and cause disturbances, stimulate sweating/salivation

TCo:

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14
Q

Nicotine

A

M: nicotinic agonist (tertiary amine)

CA: smoking cessation therapy

AE: increase HR/BP (catecholamine release); N/V/D, voiding of urine, salivary/bronchial secretions; Acute Nicotine Poisoning same symptoms except BP drops

TCO: low doses causes parasympathetic and sympathetic ganglionic depolarization resulting is discharge symptoms from both systems; In high doses caused ganlionic blockade (including neuromuscular) from prolonged depolarization

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15
Q

What is the MOA of indirect-cholinergic agonist (anticholinesterases)?

A

Inhibit acetylcholinesterase thereby increase the concentration of endogenous acetylcholine

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16
Q

What are the 3 chemical groups of indirect-acting cholinergic agonsist (anticolinesterases)?

A
  1. Edrophonium
  2. Carbamates
  3. Organophosphates
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17
Q

Edrophonium

A

M: reversibly binds active site of acetylcholinesterase (Quaternary ammonium)

CA: diagnosis of myasthenia gravis by increase ACh concentrations to reverse the non-depolarizing muscular blockers

AE: excessive muscarinic stimulation (salivation, lacrimation, miosis, diarrhea, bradycardia) excessive nicotinic stimulation (muscle weakness, paralysis)

TCo: short lived (2-10 minutes)

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18
Q

What are the 3 carbamates?

A
  1. Neostigmine
  2. Physostigmine
  3. Pyridostigmine
19
Q

Physostigmine (carbamate)

A

M: covalent bond with acetylcholinesterase (tertiary amine)

CA: Tx of anticholinergic drug overdoses

AE: excessive muscarinic stimulation (salivation, lacrimation, miosis, diarrhea, bradycardia) excessive nicotinic stimulation (muscle weakness, paralysis)

TCo: can penetrate BBB so can effect CNS causing convulsions and bradycardia

20
Q

Neostigmine

A

M: covalent bond with acetycholinesterase; Quaternary amine (does not enter CNS)

CA: reversal of non-depolarizing neuromuscular blockers after surgery, symptomatic treatment of myasthenia gravis, prevention/tx or p/o distention and urinary retention

AE: salivation, flushing, low BP, nausea, abd pain, diarrhea, bronchospasm

TCo:

21
Q

Pyridostigmine

A

M: covalent bond with acetylcholinesterase (quaternary amine, does not enter CNS)

CA: treatment of myasthenia gravis (most common)

AE: excessive muscarinic stimulation (salivation, lacrimation, miosis, diarrhea, bradycardia) excessive nicotinic stimulation (muscle weakness, paralysis)

TCo:

22
Q

What are the organophosphates drugs?

A
  1. Echothiophate
  2. Parathion
  3. Malathion
  4. Tabun
  5. Sarin
  6. Soman
23
Q

Echothiophate

A

M: phosphorylate the active site of the acetylcholinesterase

CA: rarely used for open-angle glaucoma

AE: excessive muscarinic stimulation (salivation, lacrimation, miosis, diarrhea, bradycardia) excessive nicotinic stimulation (muscle weakness, paralysis)

TCo: only organophosphate that is not liposoluble

24
Q

Thiophosphate Insecticides

A

Malathion and Parathion

M: phosphorylate acetylcholinesterase

CA:

AE: malathion is for public use; parathion is not for general public

TCo: activated in body to conversion to oxygen anologs

25
Q

Nerve Agents

A

Tabun, Sarin, Soman

M: phosphorylate acteylcholinesterase

CA:

AE: CNS toxicity

TCo: among most potent synthetic toxic agents

26
Q

Acetylcholinesterase Inhibitors used in Alzheimer disease

A

Donepezil, Rivastigmine, Galantamine

M: orally active centrally acting inhibitors of acetylcholinesterase

CA: treatment of Alzheimer’s disease

AE:

TCo:

27
Q

Pralidoxime

A

M: split the phosphate-enzyme bond to reactivate inhibited acetylcholinesterase

CA: cholinesterase regenerator for organophosphate insecticide poisoning (ineffective in CNS)

AE:

TCo:

28
Q

What are the Belladonna Alkaloids?

A

Atropine and Scopolamine

29
Q

Atropine

A

M: muscarinic receptor competitive antagonist (tertiary amine)

CA: antisialogogue prior to surgery (decrease respiratory secretions), increase HR or decrease AV-block, overdose of cholinergic drugs, to alleviated muscarinic side effects of anticholinesterase drugs

AE: dry mouth, blurred vision, sandy eyes, tachycardia, constipation; CNS (restlessness, confusions, hallucinations, delirum, depression, and collapse of circulatory/respiratory system and death)

TCo: both central and peripheral muscarinic blocker

30
Q

Scopolamine

A

M: muscarinic receptor antagonist

CA: anti-motion sickness drugs, mydriasis/cycloplegia for diagnostic procedures, block short term memory

AE:

TCo: CNS and PNS

31
Q

What are the two types of synthetic/semisynthetic drugs and what specific drugs belong to them?

A
  1. Quaternary Ammonium Muscarinic Antagonist
    1. Ipratropium and Tiotropium
  2. Tertiary Amine Muscarinic Antagonist
    1. Homatropine and Tropicamide
    2. Benztropine and Trihexyphenidyl
32
Q

Ipratropium and Tiotropium

A

M: muscarinic antagonists (quaternary ammonium)

CA: inhalation drugs for COPD and asthma

AE:

TCo: contraindicated towards angle-closure gluacoma, prostatic hypertrophy, and the elderly

33
Q

Homatropine and Tropicamide

A

M: muscarinic antagonist (tertiary amine)

CA: mydriatic for fundoscopy, mydriasis with cycloplegia (better than atropine because shorter action)

AE:

TCo: contraindicated in pts with angle-closure glaucoma, prostatic hypertrophy, and in the elderly

34
Q

Benztropine and Trihexyphenidyl

A

M: muscarinic antagonist (tertiary amine)

CA: treats Parkinson’s disease and the extrapyramidal effects of antipsychotic drugs

AE:

TCo: contraindicated in pts with angle-closure glaucoma, prostatic hypertrophy, and in elderly

35
Q

Glycopyrrolate

A

M: antimuscarinic (quaternary ammonium)

CA: orally to inhibit GI motility, parenterally to prevent bradycardia during surgical procedures

AE:

TCo:

36
Q

Tolterodine

A

M: antimuscarinic

CA: overactive bladder

AE:

TCo:

37
Q

What are the 2 mechanisms of a ganglion blockade?

A
  • Prolonged depolarization
  • By antagonisms of nicotinic receptors (Hexamethonium and Mecamulamine)
38
Q

What are the 2 types of neuromuscular blockers?

A
  • Competitive antagonists (nondepolarizing blockers)
  • Agonsists (depolarizing blockers)
39
Q

Tubocurarine

A

M: competitive antagonist of nicotinic receptors (nondepolarizing blockers)

CA: adjuvant drugs in anaesthesia during surgery to relax skeletal muscle

AE:

TCo:

40
Q

Succinylcholine

A

M: binds to nicotinic receptor and depolarized the junction, persists in the synaptic cleft stimulating the receptor: receptor desensitizes which leads to flaccid paralysis

CA: rapid endotracheal intubation, ECT

AE: malignant hyperthermia (excessive calcium relase from SR), most incidents due to combination of succinycholine and halogenated anesthetic which can be treated by Dantrolene (blocks Ca2+ relase from SR)

TCo:

41
Q

What are the drugs that act presynaptically?

A
  • Hemicholinium-3
  • Vesamicol
  • Botulinum Toxin
42
Q

Hemicholinium-3

A

M: block the CHT (Na+ dependent choline transporter)

CA:

AE:

TCo:

43
Q

Vesamicol

A

M: blocks ACh-H+ antiporter whcih transports ACh into vesicles

44
Q

Botulinum Toxin

A

M: inhibits acetylcholine relase

CA: treatment of disease involving muscle spasms, cosmetic treatment

RCS (8 decks)

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