Lecture 13 - Cholinergic Antagonists Flashcards
What are the muscarinic antagonists? (six)
Atropine Scopolamine Glycopyrrolate Oxybutynin Ipratropium Tropicamide
What are the non-depolarizing NMJ blocking agents? (five)
D-tubocurarine Pancuronium Vecuronium Cisatracurium Atracurium
What are the depolarizing NMJ blocking agents? (one)
Succinylcholine
What does atropine come from?
Belladona/nightshade
What does scopolamine come from?
angels trumpet
What is the general distribution of atropine?
Only gets into CNS with very high doses
Mostly peripheral effects
About how long does atropine last in dogs?
30 min
What is the general distribution of scopolamine?
CNS!
What effects do you see with scopolamine?
Euphoria + Sedation + Amnesia
What determines the effects of atropine at a certain organ?
Dose
Prevailing tone
Distribution of M receptors
How do rabbits react to atropine?
Resistant, have special enzyme to metabolize quickly
How do goats, cattle, and horses react to atropine?
Can eat the plant, but injected atropine can be VERY toxic
How do swine react to atropine?
very sensitive, can’t even eat it
What are the general CNS effects of atropine?
Confusion + Coma
What are the toxic CNS effects of scopolamine?
Hallucinations + Delirium + Coma
What is the normal state of the eye?
PNS - slightly rounded lens + slightly constricted pupil
What does muscarinic antagonist do to the eye?
PNS decreased
Pupil dilated - via circular muscle
Lens flattens - via ciliary muscle
What is mydriasis?
Dilation
What is miosis?
Constriction
What side effects do you see with muscarinic blocked in the eye?
Photophobia + Blurry vision + Dry eyes
What type of muscarinic receptor is on the heart?
M2
What does M2 do at the heart?
ACh stimulates M2 on the heart at SA node
Pre-synaptic M2 decreases NE
Both decrease heart rate
What does muscarinic blockade due to the heart?
Tachycardia
When is atropine used in relation to the heart?
Cardiac arrest
What do cholinergic antagonists do to respiration?
Reverse bronchoconstriction
–or–
Bronchodilation
When is a cholinergic antagonist used in regards to respiration?
RAO or Heaves
What cholinergic antagonist is used for heaves?
Ipratropium
What does muscarinic blockade do in the GI tract?
Decrease motility + secretions
Decrease tone of bile duct
What does muscarinic blockade do to the bladder?
Decrease bladder motility
Decrease tone of ureter
What does muscarinic blockade do to the uterus?
Depress hypertonicity
What is a cholinergic antagonists used for during surgery?
Decrease secretions
What is a common side effect with cholinergic antagonists?
Dry mouth
What is the general effect of cholinergic antagonist in regards to secretions?
Dry eyes + Lack of sweating
What is used to reverse bradycardia in sx?
Atropine
What is used to prevent/treat post-operative bradycardia ?
Glycopyrrolate
What is something you have to watch out for with Glycopyrrolate?
Colic in horses
What is used for decreasing GI hypermotility + spasms?
Glycopyrrolate + Propantheline
What is used to decrease bladder activity + incontinence?
Oxybutynin
What is used to treat anterior uveitis?
Atropine
What is used in corneal ulceration treatment to decrease pain?
Atropine
What is used to cause mydriasis for intraocular exam?
tropicamide
How does tropicamide act differently in horses?
lasts for up to 12 hours
What is used to decrease respiratory secretions in surgery?
Atropine + Glycopyrrolate
What is used in treatment of organophosphate poisoning?
Atropine
What are the common side effects with cholinergic antagonists?
Dry mouth Decrease secretions Tachycardia with possible arrhythmias Mydriasis + Cycloplegia Decreased GI motility
What is the phrase for atropine overdose?
Dry as a bone
Blind as a bat
Mad as a hatter
What do you see with atropine overdose specifically?
Hot + Dry Constipated + Urinary retention Dilated pupils + blurred vision Tachycardia Aggitation + Delirum Cardiovascular + respiratory collapse
What is used to treat atropine overdose?
AChE inhibitors
Physostigmine to increase CNS ACh
What are the two types of Neuromuscular blockers?
Depolarizing
– and –
Non-depolarizing
What do the depolarizing NM blockers do?
Stimulate a muscular contraction before blocking the receptor
What do the non-depolarizing NM blockers do?
Competive antagonists
Direct blockade of channel occurs with no contractions
What are NM blockers used for?
paralysis with surgery
What is the onset of action for non-depolarizing NM blockers?
1 to 6 minutes
What is the distribution of non-depolarizing NM blockers in the CNS? Why?
Not able to get to CNS
Highly ionized
What can reverse non-depolarizing NM blockers?
Cholinesterase inhibitors to increase ACh levels enough to overcome blocker
What is the most common non-depolarizing NM blocker to use?
Atracurium
What is atracurium broken down by?
Plasma cholinesterase
How does cisatracurium compare to atracurium?
More potent
Less likely to cause histamine release
What are the long acting non-depolarizing drugs?
d-tubocurarine
pancuronium
What are the intermediate non-depolarizing drugs?
Vecuronium
Atracurium
Cisatracurium
What is the duration of the long action non-depolarizing drugs?
2 to 3 hours
What is the duration of the intermediate non-depolarizing drugs?
30 to 90 minutes
What is the progression of paralysis with the non-depolarizing drugs?
Small muscles
Larger muscles
Deglutition + Laryngeal + Abdominal intercostal muscles
Respiratory muscles
How long does succinylcholine last?
5 ot 10 minutes
What is succinylcholine used for?
Short procedures
What animals are resistant to succinylcholine?
Horse + Pigs
What ion is important to watch out for with use of succinylcholine?
K+
What does succinylcholine do in regards to K+?
Increases release of K+, leading to hyperkalemia in dogs who are already sick = cardiac arrest
What effect does tetracylines + aminoglycosides have on ACh release?
Decreased
reverse with Ca but NOT neostigmine
What effect does Polymixins have on ACh?
Decrease post-synaptic sensitivity
What effect does clindamycin have on muscle?
Inhibits, cannot be reverse with Ca or neostigmine
