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cholinergic agonist Flashcards

1
Q

types of cholinesterases

A

acetylcholinesterase and plasma cholinesterase

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2
Q

acetylcholinesterase

A

-located in synapses
-substrate selectivity: ACh

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3
Q

plasma cholinesterase

A

-located in plasma (non neuronal)
-substrate selectivity: ACh, succinylcholine, local anesthetics (procaine)

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4
Q

cholinesterase and hydrolysis of ACh

A

-AChE has the highest turnover rate of any known mammalian enzyme
-AChE hydrolyzes ACh molecules with a turnover time of 150 microseconds, ~5,000 times per second!
-The reaction requires water. Three amino acid residues that form a catalytic triad (esteric site)

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4
Q

anticholinesterase reversible agents

A

-Alcohol: edrophonium
-carbamates: Physostigmine, neostigmine, pyridostigmine
-others: donepezil (aricept)

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5
Q

anticholinesterase irreversible agents

A

-organophosphates: echothiophate (used in glaucoma), sarin (nerve gas, chemical warfare agents), malathion (pesticide, head lice)

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6
Q

acetylcholinesterase inhibitor edrophium

A

-tensilon
-quaternary ammonium alcohol
-simplest structure
-bind to anionic site and block ACh binding
-reversible
-non-covalent

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7
Q

acetylcholinesterase inhibitor neostigmine, pyridostigmine, and physostigmine

A

-carbamates
-quaternary or tertiary ammonium groups
-reversible
-covalent modification to AChE
-more slowly hydrolyzed than ACh

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8
Q

action of AChE inhibitors: edrophonium, neostigmine, pyridostigmine

A

-inhibition of acetylcholinesterase:
-Edrophonium via noncovalent, reversible
-“stigmines” as substrates that are more slowly hydrolyzed than ACh
-Does NOT readily cross BBB

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9
Q

clinical use of neostigmine

A
  • Used for MG, reversal of nondepolarizing neuromuscular blockade,
  • post-op urinary retention
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9
Q

problems of Edrophonium, Neostigmine, Pyridostigmine

A

excessive cholinergic receptor activation

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9
Q

action of physostigmine

A

Inhibition of acetylcholinesterase:
“stigmines” as substrates that are more slowly hydrolyzed than ACh

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9
Q

clinical use of edrophonium

A

very short-acting (minutes); diagnosis of Myasthenia Gravis (MG) (skeletal muscle weakness due to loss of skeletal muscle nicotinic receptors because of autoimmune disease)

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10
Q

clinical use of pyridostigmine

A

-Used in the treatment of MG, reversal of nondepolarizing neuromuscular blockade,
pretreatment for potential nerve gas exposure (occupy AChE so that nerve gas has nowhere to go)

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10
Q

clinical use of physostigmine

A

Physostigmine (can cross blood-brain barrier): Antidote to antimuscarinic poisoning

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10
Q

problems of physostigmine

A

excessive cholinergic receptor activation

11
Q

isofluorophate and echothiophate

A

-organophosphates (most are toxic)
-irreversible
-covalent modification to AChE
-longer acting
-used in the treatment of glaucoma

12
Q

action of echothiphate

A

inhibiton of acetylcholinesterase: long-acting (essentially irreversible)

13
Q

problem of echothiophate

A

Excessive cholinergic receptor activation (including miosis)

13
Q

sarin and soman

A

-organophosphate
-nerve gases
-irreversible
-covalent modification to AChE

14
Q

clinical use of echothiophate

A

-Originally for glaucoma (increase ACh and enhance muscarinic activation and subsequent outflow of aqueous humor)
-Not used currently due to availability of better drugs

15
Q

malathion and diazinon

A

-organophosphate
-insecticides
-irreversible
-covalent modification to AChE
-rapidly inactivated in mammals

15
Q

biotransformation of insecticides

A

malathion to malaoxon by Cyt P450 and insects

16
Q

antidote for AChE “poisoning”

A

-pralidoxine chloride
-antidote for pesticide or nerve gas poisoning
-most effective if given within a few hours of exposure

17
Q

action of pralidoxime (2-PAM)

A

-Strong nucleophile – will hydrolyze organophosphate IF TREAT BEFORE AGING OCCURS – this will regenerate acetylcholinesterase DOSE NOT CROSS THE BLOOD-BRAIN BARRIER (thus combine with the
muscarinic receptor antagonist atropine)

18
Q

Alzheimer’s

A

-most common cause of dementia after age 50
-atrophy of the brain
-widening of sulci and thinning of gyri
-improper processing of beta-amyloid precursor protein leads to toxic form beta A42 that promotes apoptosis
-loss of cholinergic neurons in the brain

18
Q

clinical use of pralidoxime (2 PAM)

A

treatment of organophosphate toxicity

19
Q

drugs for alzheimer

A

-donepezil (aricept)
-rivastigmine (exelon)
-galantamine (razadyne)
-memantine: donepezil and memanthine (namzaric)

20
Q

treatment of alzheimers by donepezil

A

-bind to anionic site and block ACh binding
-reversible, so non covalent
-enhances cognitive ability
-does not slow the progression of the disease
-approved to treat all stages of Alzheimers

21
Q

treatment of alzheimers by rivastigmine

A

-reversible carbamate AChE inhibitor
-enhances cognitive ability by increasing cholinergic function
-loses effectiveness as disease progresses
-side effects: nausea, vomiting, anorexia, and weight loss
-newer long-acting carbamate eptastigmine

22
Q

treatment of alzheimers by memantine

A

-N-methyl-D-asparate (NMDA) receptor antagonist
-NMDA receptors are activated by glutamate in the CNS in areas associated with cognition and memory
-neuronal loss Alzheimer’s may be related
to increased activity of glutamate
-Glutamate regulators to improve memory,
attention, reason, language and the ability
to perform simple tasks
-May slow progression of the disease,
approved for moderate-to-severe disease
-Favorable adverse effect profile

23
Q

DUMBBELs

A

Diarrhea
Urination
Miosis
Bradycardia
bronchoconstriction
emesis
lacrimation
salivation and sweating

24
Q

SLUD

A

salivation
lacrimation
urination
defecation

25
Q

contraindication to the use of parasympathomimetic drugs for asthma and COPD

A

increase bronchoconstriction

26
Q

contraindication to the use of parasympathomimetic drugs on coronary deficiency

A

further lower heart rate

26
Q

contraindications to the use of parasympathomimetic drugs on peptic ulcar

A

would increase acid secreation

27
Q

contraindications to the use of parasympathomimetic drugs on construction of the urinary or GI tract

A

if increased contraction does not remove an obstruction

28
Q

Contraindication to the use of parasympathomimetic drugs on epilepsy

A

M1Rs
CNS penetrable drugs

pt (17 decks)

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