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
If given a toxic dose ( > 10 mg) of atropine what would you observe in the CV system?
Intraventricular conduction block that inhibits electrical pulse generation in pacemaker nodes
–> leads to death
What are some therapeutic uses for antimuscarinics in the cardiovascular system?
Increase HR in pts w/ acute MI, SA or AV node dysfunction in which there is an unwanted bradycardia
What dose level should be used to treat patients with unwanted bradycardia?
Moderate doses of atropine so as to block M2 receptor
What effects do antimuscarinics have on the respiratory system?
- Cause bronchodilation
2. Reduce/dry up secretions
What two respiratory diseases are treated with antimuscarinics. What are the two drugs used to treat these diseases?
COPD and Asthma
Ipratropium or tiotropium used in inhaler or nebulizer form
What drugs are useful to dry up respiratory secretions?
Atropine or scopolamine
List the effects of antimuscarinic drugs on the GI tract
- Reduced motility, prolonging gastic empthying
- Reduce salivary secretion –> xerostomia
- Reduce GI secretions