Exam II: Cholinergic Antagonists Flashcards
What are the two groups of anticholinergics? (Cholinergic antagonists)
- Muscarinic
2. Nicotinic
What are muscarinic antagonists also called?
Parasympatholytic or antimuscarinic
An example of a parasympatholytic or antimuscarinic is…
Atropine
Describe the actions of atropine
- Reversibly block muscarinic receptors
2. Typically block actions of exogenously administered cholinergics > endogenous acetylcholine
What tissues are most sensitive to atropine?
Salivary
Bronchial
Sweat Glands
What are the tissues effected by atropine?
Eye CV System Respiratory system GI tract GU tract Sweat glands CNS
Examples (3) of nicotinic anticholinergics
- Tetraethylammonium
- Tubocurarine
- Succinycholine
Which antimuscarinic is better to elicit CNS effects: atropine or scopolamine?
Scopolamine
Atropine is hydrophillic and cannot cross BBB well so it has a minimal effect
What does scopolamine cause at therapeutic doses? At toxic doses?
Therapeutic doses:
- -> drowsiness
- -> amnesia (if pt is sensitive)
Toxic doses:
- -> CNS excitement
- -> Agitation
- -> Hallucination
- -> Coma
What are two common therapeutic uses for antimuscarinic agents?
Treatment of Parkinson’s Disease
Treat motion sickness
What drug(s) are used in tx of Parkinson’s Dz
Benzotropine (antimuscarinic agent) along with a dopamine precursor drug (levodopa)
What drug(s) are used to treat motion sickness
Scopolamine
injected, oral, or transdermal patch
What effects do antimuscarinics have on the eye?
- Relax papillary constrictor –> mydriasis (dilation of eyes)
- Relax ciliary muscle –> cycloplegia (loss of accommodation)
- Reduces lacrimal secretion –> dry eyes!
Are antimuscarinincs indicated in patient’s w/ narrow angle galucoma?
NO!
Why would we use an antimuscarinic on the eye?
Useful for ophthalmologists to view the retina with the eye dilated and cycloplegia (given as drops)
If given a low dose (0.5 mg) of an antimuscarinic (atropine) what would you observe in the CV system?
Bradycardia
Low doses only block M1 receptors; M3 receptors still stimulated by ACh on SA node to create slowed HR
If given a medium to high dose (1-5 mg) of an antimuscarinic (atropine) what would you observe in the CV system?
Tachycardia
Blocks M2 receptors in SA and AV nodes, which usually slow HR