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Foundations 2 > Cholinergic Agents > Flashcards

Cholinergic Agents Flashcards

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1
Q

muscarine

A

a poisonous substance found a a mushroom that mimics the effects of ACh

results in smooth muscle contractions, secretion, decreased heart rate, fall in blood pressure

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2
Q

atropine

A

blocks muscarinic response to ligand

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3
Q

nicotine

A

increases heart rate and blood pressure, mimics the effects of ACh in large doses or when injected with atropine, which blocks the muscarinic receptors

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4
Q

tubocurarine

A

blocks nicotinic receptors

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5
Q

structure-activity relationship (SAR) for acetylcholine

A

has nicotinic and muscarinic sides

the more substituents added to the molecule, the more muscarinic it becomes

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6
Q

acetylcholine as a direct-acting parasympathomimetic agent

A

mimics the effects of parasympathetic stimulation

slows heartrate through SA node

G-protein receptors opens potassium channels and generates the outward potassium currents to hyperpolarize the membrane

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7
Q

SA node pacemaker

A

driven by the funny current (pacemaker potential)

calcium channels activated by hyperpolarization and a potassium curve repolarizes the cells

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8
Q

three ways that vagal stimulation can decrease the heart rate

A

activation of potassium channels

inhibition of funny current

inhibition of L-type calcium currents

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9
Q

parasympathetic function at the AV node

A

ACh decreases AV conduction by an increase in gK (potassium conductance)

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10
Q

effect of ACh on blood vessels

A

even though there is no parasympathetic innervation on blood vessels, ACh can cause dilation through receptors that are in the endothelium

results in EDRF (NO) release and relaxation of smooth muscle

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11
Q

effect of a low dose of ACh alone

A

produces vasodilation and a reflex tachycardia in response to the decrease in blood pressure when injected IV

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12
Q

effect of ACh and neostigmine

A

much larger fall in blood pressure due to vasodilation and decrease in heart rate when injected IV

high doses in the vicinity of muscarinic receptors may be able to overcome the reflex

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13
Q

effects of ACh and neostigmine and atropine (a muscarinic blocker)

A

only increases blood pressure and heart rate are observed

removal of the muscarinic link leaves only the sympathetic division, which is then activated by the direct action of ACh on sympathetic ganglia

sustained effects eventually are produced from epinephrine after norepinephrine effects terminate

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14
Q

Why isn’t acetylcholine used clinically?

A

non-specific

rapid hydrolysis

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15
Q

methacholine

A

methyl group on beta carbon atom of ACh, making it more resistant to ACh and more specific for muscarinic receptors

metacholine challenge used to detect bronchial asthma

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16
Q

bethanechol

A

combines structural features of methacholine and carbachol

specific for muscarinic receptors and resistant to hydrolysis by esterases

therapeutic uses - treatment with disorders of low bowel tone (adynamic ileus) and urinary retention problems

contraindications - effect on heart can produce shock, asthmatics, hyperhtroid patients susceptible to arrhythmias, peptic ulcers, intestinal or bladder obstruction

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17
Q

adynamic ileus

A

absence of motility due to decreased activity of the autonomic nervous system - GI tract

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18
Q

pilocarpine

A

mimics the effects of acetylcholine - muscarinic activator

tertiary amine with the important part of its structure following the structure-activity relationship (SAR) for muscarainic receptors

natural alkaloid and not hydrolyzed by cholinesterases

therapeutic use - glaucoma therapy, dry mouth - sjogren’s syndrome (autoimmune disease of exocrine glands)

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19
Q

cevimeline

A

acetylcholine mimic

newer agent with more efficacy than pilocarpine to treat symptoms of Sjogren’s syndrome

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20
Q

glaucoma

A

disease associated with increased intraocular pressure resulting in blindness

increased pressure can be caused by increased synthesis and/or decreased outflow of aqueous humor

AH synthesis in ciliary body -> AH in anterior chamber -> AH to trabecular meshwork to canal of Schlemm -? AH out of the eye through the venous system

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21
Q

narrow angle glaucoma

A

acute, congestive

filtration angle is markedly reduced, impairing the exit of AH, drug pretreatment is required prior to surgery

pilocarpine contracts circular muscle fibers, pulls iris toward the center of the eye and uncrowds the angle

other agents prior to surgery are anti-cholinesterases, acetazolamide or methazolamide or dichlorphenamide, mannitol

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22
Q

open angle glaucoma

A

no physical obstructrion, but the trabecular meshwork has poor tone and is misaligned

tone is improved by pilocarpine and helps add tone and open the pores

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23
Q

surgical treatments for glaucoma

A

narrow angle - laser iridotomy

open angle - laser trabeculoplasty

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24
Q

anti-cholinesterases

A

indirect-acting parasympathomimetic agents (drugs which potentiate the action of endogenous ACh at muscarinic receptors)

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25
two types of cholinesterases
true, specific or acetylcholinesterase - localized to cholinergic synapses and red blood cells pseudo, non-specific or butyryl cholinesterases - all over
26
general symptoms of poisoning with anticholinesterase agents
**S**alivation **L**acrimation **U**rination **D**efecation "SLUD syndrome"
27
toxicity of irreversible cholinesterase inhibitors
ACh is released in unphysioligically high amounts due to activation of presynaptic nicotinics - high calcium permeability this causes the nerve to fire and increase the ACh concentration even more
28
CNS symptoms of cholinesterase poisoning
anxiety, headache, tremors, conusion, violent activity, convulsions, coma, depression of respiratory and CV centers, cyanosis, fall in blood pressure
29
-stigmine
reversible cholinesterase inhibitor
30
physiostigmine
reversible cholinesterase inhibitor tertiary amine, can cross the blood brain barrier duration about 1-2 hours oral or parenteral administration therapeutic uses - glaucoma therapy, as an antidote
31
neostigmine
reversible cholinesterase inhibitor quaternary so no CNS effects duration 2-4 hours oral or parenteral administration
32
therapeutic uses of neostigmine
treat myasthenia gravis reverse non-depolarizing block at the end of surgery miotic glaucoma therapy treat urinary retention treat GI stasis, most common autonomic use
33
pyridostigmine bromide
reversible cholinesterase inhibitor same as neostigmine except available in slow release form for long-lasting 4-12 hour oral effect, useful at bedtime
34
edrophonium
duration only 5-15 minutes generally IV but you can give IM therapeutic uses - to test for MG and distinguish from cholinergic chrisis
35
contraindications of reversible cholinesterase inhibitors
asthma, hyperthyroid patients, ulcers, GI or bladder obstruction similar to those of bethanecol other features - all are hydrolyzed by liver cholinesterase quaternary agents have direct stimulatory action on the ACh receptor in addition to inhibiting cholinesterase
36
mechanism of ACh hydrolysis by ChE
ACh anchors at the anionic site of ChE, enzyme activity is at the esteratic site interaction of ACh with the esteratic site causes a rearrangement of the complex leaving an acetylated enzyme and a free choline the acetylated enzyme then reacts with water to free the acetic acid and regenerate the enzyme
37
mechanism of reversible icholinesterase inhibitorsn
molecules have slower hydrolysis after the conformational change of the enzyme to cleave the molecule usually leaves the enzyme carbamylated and is hydrolyzed very slowly
38
mechanism of edrophonium
combines electrstatically at theanionic site of ChE and hydrogen bonds to the imidazole of histidine at the esteradic site transient inhibition
39
DFP mechanism
reacts only with the serine residue of the steratic site to fomr a phosphorylated enzyme which does not hydrolyze at all resynthesis of the enzyme is necessary to restore ChE, a process which takes 3-6 weeks
40
DFP
diisopropyl phosphorofluroidate prototype agent used as nerve gas by British and Americans in WWII oily liquid that is absorbed by every route, including skin effects similar to those of physostigmine
41
Tabun and Sarin
both synthetic nerve gasses made in Germany during WWII as insecticides SARIN is structurally DFP minus one isopropyl group irreversible inhibition of cholinesterases
42
parathion
agricultural insecticide metabolized to paraoxon, the toxic form that inhibits ChE responsible for many poisonings and deaths
43
malathion
insecticide slightly safer than parathion because higher animals can metabolize this faster than parathion
44
chlorpyrifos
extremely popular insectiside in garden products and in pet flea collars for many years
45
VX
the deadliest of nerve gases, 2.5 million tons in Newport still being cleared, terrorism in Japan, Gulf War, etc.
46
treatment of toxicity
1) decontaminate (remove from skin) 2) block excess muscarinic activity with atropine (a lot is needed) 3) treat skeletal muscle effects through artificial respiration or reactivation of the enzyme 4) yridostigmine (not good!) 5) anticonvulsants if severe (diazepam)
47
2-PAM and mechanism
aka pralidoxime designed on theoretical bases, reactivates ChE by first attaching to anionic site and then binding to the P atom of the inhibitor and removing the inhibitor from the esteratic site predominant effect is at skeletal neuromuscular junction with much less effect occurring at muscarinic neuro-effector sites
48
anticholinergic agents
muscarinic antagonists - agents that block actions of ACh at cholinergic neuro-effector sites ganglionic blockers - block nicotinic receptors on autonomic ganglia
49
atropine
a belladonna alkalid from deadly nightshade prototype drug acts as a competitive inhibitor at muscarinic receptors effects are opposite to those of parasympathetic stimulation causes pupillary dilation, bronchiolar dilation, constipation, urinary retention, decreased secretions, etc. decreased sweating as well, increases heartrate at clinical doses
50
therapeutic uses for atropine
- mydriatic and cycloplegic for eye exam - COPD treatment - GI and urinary bladder spasms - blockade of secretions - increase heart rate - antidote for cholinesterase poisoning - Parkinsonium effect of atropine is generally too long to be practical and other derivatives are employed instead may precipitate an attack of narrow angle glaucoma
51
accommodation
object moves toward eye -\> CNS reflex -\> parasympathetic firing is increased -\> lens is allowed to round into its natural shape to focus on the approaching object
52
cycloplegia
paralysis of accommodation, lens fixed for distant vision
53
cyclospasm
spasm of ciliary muscle and blurred vision
54
atropine treatment of bronchioles
treat COPD can also treat asthma with atropine-like agents such as **ipratropium** and **tiotropium**
55
atropine treatment of GI spasms
spasms of smooth muscle cause pain known as cholic, relieved by atropine current drug of choice can also treat enuresis in children
56
atropine treatment of blockade of secretions
respiratory secretions acid secretions, may be used synergeistically with antibiotics and proton pump inhibitors adjunct to surgical procedures such as intubation
57
atropine to increase heart rate
during stage 2 of anesthesia during spinal anesthesia
58
Parkinsonism
atropine was a popular treatment in the past, superseded by L-dopa symptoms of parkinsonism can be alleviated by blocking the ACh effects or increasing hte effects of dopamine
59
homatropine
derivative of atropine with a shorter duration of action
60
scopolamine
similar to atropine but has an additional oxygen on one of the rings, more CNS depressant effects at usual therapeutic doses has been used int he past for sedative hypnotic effects in conjunction with opiod analgesics not effective when severe pain is present very effective against motion sickness
61
effects of muscarinic receptor blockers
anti-emetic - targets muscarinic receptors in the vestibular nucleus and the vomiting center seadation - blocks the muscarinic receptors int he cholinergic basal forebraine and mesopontine cholinergic nuclei associated with the reticular activating system amnesia - blocks muscarinic receptors in the septo-hippocampal projection
62
symptoms of belladonna toxicity from atropine and scopolamine
**Dry** as a bone -decreased secretions, urinary retention **Red** as a beet - cutaneous vasodilation due to histamine and/or compensatory effect due to increased body temeprature **Mad** as a hatter - delierium, hallucinations, eventually coma **Hot** as a stove - increased body temperature (decreased sweating) **Blind** as a bat - mydriasis, cycloplegia
63
treatment of atropine toxicity
emesis if mental status is not severely impaired gastric lavage even as late as 24-48 hours after ingestion activated charcoal after gastric emptying if anticholinergic effects are severe use an antidote - physostigmine
64
drugs for overactive bladder
tolterodine fesoterodine oxybutynin solifenacin darifenacin
65
drugs for ocular defects
cyclopentolate tropicamide homatropine
66
drugs for Parkinson's disease
benztropine trihexyphenidyl
67
drugs for bronchiolar dilation in asthmatics and COPD
ipratropium - quaternary, blocks ganglia, produces effective bronchiolar dilation without impairing mucilliary clearance tiotropium - treats COPD, superior to ipratropium because it does not block presynaptic inhibitory muscarinic receptors as ipratropium does
68
drugs for spasms of GI tract
atropine lomotil glycopyrrolate
69
ganglionic blocking drugs
basic processes involved are essentialyl the same as the processes for skeletal neuromuscular junctions block the action of ACh at autonimc ganglia both sympatetic and parasympathetics are blocked particular effect observed depedns on whcih system controls ther esting tone of a particular organ predominatn tone is muscarinic cholinergic, mediated largely by the parasympathetic division
70
ganglionic blocking drugs

Foundations 2 (33 decks)

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