Cholinergic Antagonists Flashcards
What is the prototype drug of the antimuscarinic/anticholinergic drugs?
Atropine! Could also say Scopalomine.
Compare atropine and scopolamine and their CNS entry
Atropine - enter CNS only at high doses
Scopolamine - enters CNS easily
Name effects of Atropine
Blocks msucarinic receptors
Depends on prevailing tone to start with.
Salivary, sweat, bronchioles all affected at [low]
Heart, eye
GI and GU at higher [ ]
only see CNS effects with very high doses
Explain what a muscarinic antagonist does to the eye
Think:
muscarinic antagonist will inhib PSNS action
Pupil will dilate (mydriasis)
Angle will decrease
Lens flattens –> sight affected
Eyes will be dry due to inhibited lacrimation.
Name a muscarinic antagonist with the shortest duration of action that is used on the eye?
Tropicamide - 6hrs of effect
Explain the role PSNS has on Sympathetics at the heart with respect to M2 receptors.
PSNS release Ach that will bind M2 and inhibit cAMP
NE release is decreased
K channels are opened –> hyperpolarization
Explain what a muscarinic antagonist could do to the heart.
Removes the direct effect of PSNS, so increases NE release and increases HR.
Explain Atropine’s effects on HR and BP.
low does: atropine will decrease HR
increased Ach release –> removes blockade of ACh
release by presynaptic M2 receptors
high dose: atropine will increase HR
NO EFFECT ON BP
Compare atropine’s effect on CV between young and old patients.
Young patient with lower resting HR (high vagal tone)
will see tachycardia
Older patient or BABY with higher resting HR (low vagal)
small CV effect
Name a drug that can be used to prevent vagal firing during surgery?
Glycopyrrolate
Why does atropine not have an effect on BV?
NO PSNS innervation to BV
when atropine O.D. –> see vasodilation in response to decrease the heat from increased body temp
What cholinergic antagonists act in the lungs locally?
“=tropiums”
ex: tiotropium
Acute Asthma or COPD
Can reverse bronchoconstriction
Give an example of cholinergic antagonist that works in the GI system?
Dicyclomine - antispasmodic
often give to those with IBS
Dominant tone in GI is PSNS
Name the classes of cholinergic antagonists that work in the bladder?
“-terodine” and “-fenacin”
NO CNS EFFECTS!
decrease bladder motility - helpful with overactive bladder
Ex: tolterodine
What is one problem of giving Tolterodine to men with BPH?
Exaccerbates urinary retention.
What is one danger of giving Tropicamide in the eye?
If pt has high intraoccular pressure due to glaucoma, can further narrow the angle!
Atropine can be used to decrease what heart rate phenomenon?
Atropine will decrease bradycardia
(think: muscarininc antagonist –> muscarinic would usually decrease heart)
give after MI
Name some side effects from “-terodines” and “-fenacines”
used for over active bladder treatment
since M3 antagonist –> can get side effects:
dry mouth
glaucoma
blurred vision
Name one over active bladder drug that has pharmacokinetic interactions?
Darifenacin
(Enablex)
“enables you to have big probs with other meds”
Name a good choice for post-surgery bladder issues?
Trospium
patch, keeps [ ] low and steady
less side effects
decreases bladder tone which can spasm post-op
Name a few side effects of scopolamine
Sedation
short term memory loss
euphoria if abused
toxicity has CNS effects
Common side effects of a cholinergic antagonist?
Dry mouth Decreased bronchial secretions Tachycardia (dependent on existing tone) Mydriasis Decreased GI motility Urinary retention (older men) Dry skin, decreased sweat
2 diseases that are contraindicated for cholinergic antagonist?
GLAUCOMA
BPH!
Colloquial description of an atropine O.D?
Dry as a bone
Blind as a bat
Red as a beet.
Mad as a hatter.
What is the treatment for an atropine overdose?
Supportive treatment
PHYSIOSTIGMINE! (AChE inhibitor)
It has CNS effects - which we want here!
reasoning: atropine is a cholinergic antagonist
physiostigmine will leave ACh in the cleft longer
Eventually, it will be able to act
Also - has CNS effects
What is the treatment for cholinergic agonist or AChE inhibitory toxicity?
Inject atropine until pupils dialate and mouth is dry
