Cholinergic Antagonists Part 1 Flashcards
name 2 kinds of nicotinic antagonists
ganglionic blockers
neuromuscular blockers
cholinergic antagonists will cause what kind of responses?
FIGHT OR FLIGHT
will mimic sympathetic nervous systek
explain how neuromuscular blockers work
they bind to Nm receptors on the postsynaptic membrane of skeletal muscle, PREVENTING the binding of ACh
prevents motor endplate from depolarizing - muscle paralysis
explain how ganglionic blockers work
prevent ACh (released from preganglionic neuron) from binding Nn receptor on the ganglia, in both the PSNS and SNS
explain how muscarinic blockers work
prevent ACh from binding to the muscarinic receptors on smooth muscle, cardiac tissue, secretory glands, etc
explain the history of cholinergic antagonists
from Belladonna plants - Atropa Belladona (source of atropine) and Datura stramonium
preparations of belladonna were used in ancient india and the roman empire used it as poisoning
what are the 3 classes of cholinergic antagonists?
naturally occurring alkaloids
semisynthetic derivatives of these alkaloids
synthetic derivatives
*imp to know examples
name 2 naturally occuring alkaloids that are cholinergic antagonists
atropine
scopolamine
name 2 semisynthetic derivatives of atropine and scopolamine
homatropine
some quaternary ammonium derivatives
name a synthetic derivative that is a cholinergic antagonist
ipratropium — has selectivity for some subtypes of the muscarinic receptors
explain the action of muscarinic antagonists
prevent the effects of acetylcholine by blocking its binding to muscarinic receptors
these muscarinic receptors can be on effector cells at parasympathetic Neuroeffector junctions, in peripheral ganglia, and in the CNS
TRUE OR FALSE
muscarinic antagonists are not selective
FALSE
they are selective for certain subtypes
explain the metabolism and excretion of cholinergic antagonists
half of the drug is excreted UNCHANGED in the urine (bc so hydrophilic)
the other half is hydrolyzed and conjugated and ecreted
thus, the effects are gone very quickly in all organs EXCEPT THE EYE
the effect on iris + ciliary muscles may last over 72 hours
explain the mechanism of action of atropine
a competitive (reversible) blockade of ACh at muscarinic receptors
prevents the release of IP3 and prevents the inhibition of adenylyl cyclase (M1, M3, M5)
true or false
atropine is not selective for its receptors
FALSE
it’s highly selective for muscarinic receptors
binds M1, M2, and M3 - not selective for subgroups, but selective for muscarinic in general
explain the effect of scopolamine and atropine on the CNS
Scopolamine has CNS affects like drowsiness and amnesia
atropine has minimal effect on the CNS. slow, long lasting sedative effects
in toxic doses, esp scopolamine can cause hallucination and coma
true or false
atropine is used to treat parkinsons disease
FALSE – used to decrease the TREMORS that result from parkinsons
scopolamine is used to treat…..
vestibular disturbances - motion sickness
that involves cholinergic transmissionw
what is scopolamine
a muscarinic antagonist
name 2 cholinergic inverse agonists
atropine
ipratropium
brings original action down below the baseline
true or false
atropine is highly selective for muscarinic receptors
true
selective for muscarinic receptors in general but
not selective for M1,M2,M3 – binds all 3
true or false
atropine is competitive with Ach at muscarinic receptors
TRUE
reversible and competitive
both bind to same site
true or false
scopolamine is a muscarinic antagonist
TRUE
what is mydriasis
dilation of the eye
what is cycloplegia
weakened contraction of the ciliary muscle
what drug can be used to cause mydriasis and cycloplegia?
ATROPINE ****8
true or false
atropine increase lacrimation
FALSE - decreases
that’s why used for treatment of mydriasis and cycloplegia
what is the result of atropine on the heart
causes TACHYCARDIA (fast heartbeat)
SA and AV node are very sensitive to antimuscarinics
HOW does atropine cause tachycardia
by blocking vagal slowing
true or false
atropine causes vasodilation
FALSE
vasoconstriction
true or false
atropine can cause increased blood pressure
TRUE
due to vasoconstriction + tachycardia
what is the effect of an anticholinergic on salivary secretion
decreases salivary secretion and causes dry mouth
true or false
anticholinergics cause bronchoconstriction
FALSE - bronchodilation
selective ________ agents are best for treatment of asthma and COPD
selective to M3
bronchodilation
M3 is glands, smooth muscle, and endothelium
TRUE OR FALSE
anticholinergics have no effect on the uterus
TRUE
what is the effect of anticholinergics on the genitourinary tract
the smooth muscle of the ureters and bladder wall relaxes and SLOWS VOIDING
true or false
anticholinergics contract the smooth muscle of the ureters and bladder wall and thus slow voiding
FALSE
relax this smooth muscle which slows voiding
what is the effect of atropine on sweating?
suppresses THERMOREGULATORY sweating
as mentioned, atropine suppresses thermoregulatory sweating
explain a negative effect of this
in infants and children, even normal doses can cause “atropine fever” bc the body isn’t sweating enough to cool itself down
true or false
anticholinergics increase tremors
FALSE - decrease
ex: atropine used to treat parkinson’s tremors
besides atropine, name 3 other anticholinergics used to treat the tremors from parkinsons
benztropine (cogentin)
benzhexol (Artane)
procyclidine
name 2 adverse effects of scopolamine
sedation, dry mouth
true or false
homoatropine is synthetic
false - semisynthetic
how are anticholinergics used in ophthalmic examination?
to cause mydriasis and cycloplegia (ciliary paralysis)
for adults and for older children, _____ acting drugs are preferred for ophthalmic examination
shorter
true or false
cholinomimetics are used for ophthalmic examination
false
anticholinergics
what kind of preparations are useful to prevent synechia (adhesion) formation in uveitis and iritis?
longer lasting anticholinergics like homoatropine
name 5 anticholinergics used as eye drops
atropine
scopolamine
homatropine
cyclopentolate
tropicamide
rank the 5 anticholinergic eye drops in order of duration of action
longest:
atropine
scopolamine
homatropine
cyclopentolate
shortest = tropicamide
name 2 drugs used pre-surgery to prevent laryngospasm and decrease secretions
atropine and scopolamine
name 3 drugs used in COPD
ipratropium
tiotropium
aclidinium
iprat and tio also used in asthma
true or false
to treat asthma and COPD, an anticholinergic can be used
true
graves disease
hyperthyroidism
how can atropine be used in people with graves disease?
hyperthyroidism can cause atrial fibrillation
atropine can treat
_______ can be used in myocardial infarction
atropine
bc myocardial infarction leads to bradycardia and decreased cardiac output, potentially leading to fainting
atropine can be used in patients with circulating……
cardiac M2 antibodies
what can treat traveler’s diarrhea
atropine + diphenoxylate (low dose opioid) = lomotil
how can anticholinergics be used in urinary disorders
in bladder spasm and urinary urgency, urinary incontinence
what is urinary incontinence and how can it be treated
involuntary leakage of urine bc of loss of bladder control
treated with anticholinergics
name 3 sources of cholinergic poisoning
insecticides (cholinesterase inhibitors)
wild mushrooms
chemical warfare
name 2 remedies to cholinergic poisioning
-use antimuscarinic therapy (atropine - a tertiary amine)
-use cholinesterase regenerators (pralidoxime)
true or false
there is NO way to directly block the nicotinic effects that occur bc of cholinesterase inhibition
true
only the muscarinic part - give atropine
how is it possible for pralidoxime to be used in cholinergic poisoning
pralidoxime can remove the phosphate from the enzyme-organophosphate complex bc it has a higher affinity for the phosphate
enzyme has been regenerated
what is mushroom poisoning and what is used to treat it
due to too much cholinergic activity - nausea, vomiting, diarrhea, urinary urgency, sweating, salivaiton, bronchoconstrivtion
PARENTERAL ATROPINE IS GIVEN **
when an antimuscarinic agent is used to reduce GI motility/secretion, name 2 adverse effects
mydriasis
cycloplegia
what are the results of atropine poisoning
dry mouth
mydriasis
tachycardia
hot and flushed skin
agitation
delirium for as long as 1 week
children and infants = atropine fever. very subject to hyperthermic effects
what are ganglionic blockers/ganglion blocking agents?
COMPETITIVELY block the action of ACH and similar agonists at Nn receptors of parasymp and symp autonomic ganglia
some also BLOCK THE ION CHANNEL that’s gated by the nicotinic cholinoceptor
explain the clinical use of ganglionic blockers
they can block all autonomic outflow, and have a LACK of selectivity
this, there are a lot of undesirable effects when used, and thus they have limited clinical use
true or false
ganglionic blockers noncompetitively block the action of ACh at Nm receptors of both parasympathetic and sympathetic autonomic ganglia
FALSE
competitively block at Nn RECEPTORS
(neuronal nicotinic)
name 4 ganglionic blockers***
what are they blocking?
blocking action of ACh at Nn receptors of both sympathetic and parasympathetic ganglia
hexamethonium
mecamylamine
tetraethylammonium
decamethonium
explain the structure of the ganglionic blockers
they are synthetic amines and structurally similar to acetylcholine
(remember - competes with same site ! makes sense that they’re similar)
which of the ganglionic blockers was first identified?
what is its duration of action?
tetraethylammonium
short duration
which of the ganglionic blockers was first used clinically to treat hypertension
hexamethonium
why was mecamylamine developed originally
to improve absorption from GI trat]ct
analog of hexamethonium and a depolarizing neuromuscualr blocking agent
decamethonium
