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Pharmacology - Cholinomimetics

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two types of cholinomimetic drugs - mode of action
direct-acting -bind M2,M3receptors
indirect-acting-inhibit acetylcholinesterase (anti)
acetylcholinesterase
enzyme that rapidly degrades Acetylcholine in the synaptic cleft at the NMJ
indirect acting - mode of action
anti-cholinesterase
inhibit the enzyme
reversibly and irreversibly
direct acting cholinomimetics MODE OF ACTION
receptor agonists - bind to and activate muscarine M2,M3 receptors
direct acting drugs of choline esters
Ach (miochol)
bethanechol
carbachol
methacholine
direct acting drugs -
alkaloids
muscarine (M)
pilocarpine (M)
nictotine (N)
memory trigger for choline ester
beth, meth, carb and Ach all went to see cholinester
memory trigger for alkaloids
nic piled in his muscarine and vroomed away
indirect acting drugs cholinomimetics
anti-cholinesterases
antagonists
reversible indirect-acting
Tensilolon (edrophonium)
reversible indirect-acting
carbamates (4)
demacarium
neostigmine
physiostigmine
pyridostigmine
reversible indirect-acting drugs for Alzheimers disease
donepezil
galantamine
memory trigger for the AD drugs
she's a DONE GAL
IRreversible indirect-acting anticholinesterases
--Organophosphates
echothiphate (phospholine)
Malathion
parathion
soman
memory trigger
- think military call-out
echo, mala, para, soma
what are the two main types of Glaucoma?
acute narrow angle
chronic open (wide) angle
what issues do these glaucomas create?
both increase intra-occular fluid pressure
how is aqueous humor produced?
by the ciliary body behind the peripheral edge of the iris
where does this aqueus humor flow?
medially to the posterior chamber, then anteriorly to the anterior chamber
describe flow pattern
medially toward pupil in space b/t back of iris and front of the lens, then fwd thru pupil, to speace b/t front of iris and back of cornea
what is the function of the aqueous humor?
nourish the lens of the eye
what happens if it does not exit the anterior chamber?
fluid pressure builds up and causes the riris to bulge forward creating a "narrow angle"
what happens when the aqueous humor does exit the anterior chamber?
it is absorbed by a network of trabeculae and drained into a conjunctival vein
what is the name of the conjunctival vein?
the canal of schlemm
(sinus venosus sclerae)
where is this "angle" of the eye located?
where the back of the cornea meets the front peripheral edge of the iris - and is usually wide and 'open'
what is a narrow angle?
when the irish bulges
how is a narrow angle detected?
by shining a penlight from the lateral side of the eye across the front
what is present when detecting the angle?
the bulging iris casts a shadow on the medial side of anterior chamber
what is the risk of a narrow angle?
rapid build up of fluid pressure if the pupil becomes significantly dilated
what issue is created by this risk?
as the iris contracts radially it can cause acute obstruction of fluid outflow and rapid increase in intra-ocular pressure
what causes significant eye dilation?
dark places (movie theater)
stress
drugs used in eye exams
pre-op atropine
antidepressants
nebulized brhochodilators (B2 agnosists)
how does stress affect dilation?
increased EPI secretion and sympathetic tone
what drugs are used during eye exam to cause dilation?
mydriatic drugs - mydriacyl (topicamide)
cyclogyl (cyclopentolate)
Mydriasis
dilated eyes
why is pre-op atropine an issue?
it is an anti-cholinergic drug
why do antidepressants affect dilation?
anticholinergic effects
how do nebulized bronchodilators dilate the eye?
these Beta 2 agonists cross react with Alpha1 receptors of radial muscle of iris
what are negative effects of long-term dilation?
*acute eye pain
*blurred vision
*see halos around light
*nausea/abd pain
*conjunctivitis
*stamy cornea
*dilated pupil that is unreactive to light
*permanent vision loss 2-5 days
T/F acute narrow angle glaucoma is a medical emergency?
TRUE - must treat immediately by reducing the pressure - by re-constricting the puil and reopening the angle
what drug treatment is used to treat narrow angle glaucoma?
muscarinic agonist combined with anticholinesterases
what is the effect of the general treatment?
cause ciliary muscle contraction, stretching the trabeculae, allowing for draining of fluid
what muscarinic agonists are used?
pilocarpine drops or carbachol drops
what anticholinesterases are used to treat narrow angle?
physostigmine - opth. ointmnt
echothiophate drops
demecarium drops
what other drugs are used to decrease fluid pressure?
carbonic anhydrase inhibitors
Acetazolamide
brinzolamide
why are carbonic anhydrase inhibitors used?
to decrease the fluid production
what is the effect of prostaglandins?
increase drainage of aqueous humor
what prostaglandins are used?
Lumigen (bimatroprost)
rescula (unoprostone)
does surgical treatment work?
Yes - laser peripheral iridotomy is a permanent cure
describe Chronic open angle glaucoma
simple, wide angle glaucoma - with increased intra-ocular pressure doe to inadequate drainage of trabeculae
is this a true angle problem>
no, it is an issue of inadequate drainage
what is the etiology?
unknown - idiopathic, could be familial or cx by diabetes
what secondary events could cause chronic open glaucoma?
uveitis or trauma
which glaucoma is considered to be bilateral?
chronic open angle
is surgical treatment a viable option for chronic open angle?
typically no, but laser trabeculopplasty may come into play on some
what is the recommendation for drug treatment for chronic glaucoma? (timeframe)
long term is required using alpha-agonists, beta-blockers, caronic anyhdrase inhibitors and prostaglandins
how do cholinomimetics work to treat COG?
enhance drainage of fluid by contracting ciliary muscles and stretching trabeculae
what cholinomimetic drugs are used?
muscarinic agonists
*pilocarpine, carbachol
anti-cholinesterase
-physostigmine
what carbonic anhydrase inhibitors are used?
acetazolamide
brinzolamide
what alpha agonists are used?
nonselective =EPI, and propine
alpha2 = iopidine & alphagan
what affect do the alpha agonists have?
non-selective
**INCREASE DRAINAGE
selective alpha 2
**DECREASE humor PRODUCTION
What beta blockers are used?
betaxolol (betoptic)
timolol(timoptic, betomil)
what is the function of beta blockers for this?
DEcrease humor production
what drugs decrease humor production?
*beta blockers betoptic, betomil, timoptic
*aplha2 agonists-iopidine, brimonidine
what cholinomimetics are used to counteract GI and UT smooth muscle activity depression?
muscarinic agonist
*bethanechol (uricholine)
indrect-acting (anti-cholins.)
*neostigmine
what is Post-Op Ileus?
atony or paralysis of stomach or bowel after surgery
depressed muslce activity causing urinary retention occurs from?
*post-op
*postpartum
*after spinal cord injury/disease
"neurogenic bladder"
reflux esophagitis (GERD) is treated with?
H2 blockers, bethanechol, neostigmine
What is used to treat DRY MOUTH cx by sjorgren's syndrom or other sicca syndromes?
muscarinic agonist -
cevimiline (Evoxac)
what is the relationship b/t Myesthenias gravis and receptors?
Ab-mediated reduction in the # of FX nicotinic Nm receptors of NMJ
what is used to treat MG for this?
ONLY indirect-acting anticholinesterases
-pyridostigmine
-neostigmine
-ambenomium
demercarium
LONG TERM
how is MG diagnosed?
by giving Tensilon to pt - will see decreased fatigue w/in 5 min,
how is Tensilon used regarding MG?
diagnosis
assess level of longterm tx with anitcholinesterases
what is the result of overmedicating the pt?
depolarizing blockade and excessive stimulation of muscarinic receptors
what are the signs of an overmedicated pt?
miosis
bradycardia
excessive salivation and bronchial secretions
abd pain cramps and diarrhea
how do you know if pt is over or under medicated?
by giving Tensilon -
if weakness does not improve - overmedicatd
if weakness does improve - undermedicated
are cholinomimetics useful in treating Alzheimer's Disease?
NO - but people use as a last hope and some results have been positive SHORT TERM
What cholinomimetics are prescribed for AD?
anticholinesterases
-donepezil
-galantamine
T/F AD is the result of too little Ach due to a reduction of brain neurons?
TRUE
what is the action of anesthetics during surgery?
neuromuscular blockade - imposing dysfunction of the motor endplate - cx muscle paralysis via NT dysfunction at NMJ
what drugs are used to impose this skeletal muscle paralysis? (general class)
anti-cholinergics
deoplarizing and nonpolarizing
what depolarizing drugs are used?
succinylcholine
what nonpolarizing drugs are used?
curare
attracurium
pipecuronium
pancuronium
vecuronium
(remember 3 curoniums)
trigger- who are the 3 curonium brothers and their sister?
pipe, panc, vec and sister curare
which anti-cholinergic class is used most frequently and what is its action?
non-depolarizing - they block the Nm receptors by competing w/ Ach, thereby preventing depolarization of muscle fiber membrane
T/F the muscle paralysis induced by these drugs is caused by upper/lower motor neuron dysfunction?
FALSE - it is from neurotransmitter dysfunction at the NMJ
what drug class is used to reverse this process?
anti-cholinesterases- aimed at increasing amount of Ach (and icreasing half-life) at the motor end plate
what are these drugs?
neostigmine
pyridostigmine
Tensilon
what ailments are cholinomimetics used for?
acute narrow angle glaucoma
chronic wide angle glaucoma
GI and UT activity depression
Alzheimer's Disease
Dry mouth
Myasthenias Gravis
reversal of surgical NM block
antidotes for insecticides and humanocides
What does DUMBELS represent?
( OR...DUMB3ELS)
Diarrhea
Urination
Miosis
Bronchorrhea
Bronchospasm
Bradycardia
Excitation (anxiety, fasciculation, seizures)
Lacrimation
Salivation
what is the other name for cholinomimetics?
parasympathomimetics
or cholinoreceptor activating drugs
what is the action of insecticides?
organophosphates kill via irreversible anticholinesterase activity-causing excessive parasympathetic activity-
what parasympathetic activity is induced from ingestion of insecticides?
vegetative manifestations:
miosis
salivation
hyperactive bowel sounds
lethargy
bradycardia (muscarinic axn)
or tachycardia (nicotinic axn)
death can occur from?
respiratory depression - you can NOT take IN another breath
what is the mnemonic used to describe the effects of insecticides?
DUMBELS
what does DUMBELS stand for?
Diarrhea
Urination
Miosis
Bronchorrhea
Bronchospasm
Bradycardia
Excitation: anx,fasciulations, seizures
Lacrimation
Salivation
what are the antidotes for DUMBELS?
Atropine
pralidoxime(Protopam 2-PAM)
what is the action of Atropine?
competitive muscarinic receptor blocker
M1,2,3 etc.
_reduces symptoms, may need repeated doses
what is the action of Pralidoxime? (protopam, 2pam)
competitively INHIBIT binding of organophosphates to acetylcholinesterase
(2-PAM carried by military personnel)
carbachol
cholinomimetic direct acting choline ester
Tx: narrow angle glaucoma
fx: M + N,
resistant to AchE,
Acetylcholine
cholinomimetic direct-acting
M+N shortest duration
Bethanechol
cholinomimetic direct-acting
Fx: Muscarinic
resistant to AchE,
TX: stimulates post op bladder and GI
Pilocarpine
Cholinomimetic direct-acting alkyloid
Fx: M
Tx: glaucoma, narrow angle and chronic wide
cevimeline (Evoxac)
cholinomimetic direct-acting
fx: M
tx: dry mouth from Sjogrens or sicca syndrome
nicotine
cholinomimetic direct-acting
Alkaloid
Fx: nicotinic receptor
endrophonium (Tensilon)
anticholinesterase
indirect-acting -reversible
FX: M+N
Tx: diagnostic test for myasthnia gravis
reversal of surgical NM blockade
demecarium (Humorsol)
Indirect-anticholinesterase
a carbamate
Fx: inhibit, reversible
Tx: Myastehnias Gravis
wide angle glaucoma
neostigmine
indirect-anticholinesterase - carbamate

Fx: inhibit, reversible
tx: myasthenias gravis
GI, GERD, UT post-op
reversal of surgical blockade
physostigmine
cholinomimetic indirect-acting
Fx: M+N carbamate=reversible Tx: glaucoma
echothiophate
indirect-acting M+N organophosphate
=irreversible
Tx: glaucoma
parathion
indirect-acting M+N irreversible organophosphate
longest lasting=most toxic
atropine
antidote for organophosphate insecticides
Fx: blocks M1,2,3 etc
no effect on nicotinic
curare,atracurium,pipecuronium,pancuronium, vecuronium
non-polarizing anti-cholinergic drugs used for surgical NM blockade
succinylcholine
depolarizing anti-cholinergic drug used for reversal of surgical NM blockade
what anticholinesterases are used for reversal of NM blockade post surgery?
neostigmine
pyridostigmine
Tensilon
"PEN"
pralidoxime (Protopam, 2PAM)
used by military and in hospitals to counteract DUMBELS poisoning
Fx: inhibitrs binding of organophosphates to acetylcholinesterase
what drugs decrease aqueous humor production?
beta blockers=
Betoptic, Timoptic,Betimol
carbonic anyhdrase inhibitors =
Diamox, Azopt
what drugs increase drainage of aqueous fluid to trabeculae?
non-selective alpha agonists=
EPI, Propine
Prostaglandins =
Lumigan, Rescula
memory trigger for beta blockers
Tim and Beto Bet-im-ol at the casino, and you beta their wives blocked their receptors
treatment of myasthenias Gravis can include one of the following
indirect -anticholinesterases
reversible
pyridostigmine
neostigmine
ambenonium(Mytelase)
demercarium (Humorsol)
Donepezil (Aricpet)
anticholinesterase -indirect, reversible
Tx: alzheimer disease
neurogenic bladder tx
treat with cholinomimetic
M =bethanechol (urecholine)
anti-ChE=neostigmine (prostigmin)
memory trigger
neurogenic bladder and urecholine
when you 'gotta go'
ur-e-choline for the drugs to help you out
Mytelase
generic for ambenonium for tx of MG
Humorsol
generic for demecarium
tx for MG, wide angle glaucoma (drops)
trigger for increased draining of aqueous humor
ED, please RESCULA my LUMIGAN, I AZOPT it in the DIAMOX drain and it is full o PCP's
p=pilocarpine, C-carbachol p=physostigmine
ED = epi, diivefrin
trigger for decreased humor production (tx for glaucoma)
no humor until you do your ABC's
alpha 2 agonists, beta blockers, carbonic anhydrase inhibitors
memory trigger ro decreased humor productionn - specific drug names used
IOPIDINE THE BRIMONIDINE, BETA clean my diamox beore I azopt for the night.
CAIs
acetazolamide (diamox)
brinzolamide (Azopt)
memory trigger for GI, UT, GERD
when those go crazy - some people smell like "P U" .
my mouth is dry, bring me some
cevimiline

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