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eLCRS - 팜 > PHARM 7: Cholinoceptor Antagonists > Flashcards

PHARM 7: Cholinoceptor Antagonists Flashcards

1
Q

define affinity

A

the strength with which an agonist binds to a receptor

  • to form a drug receptor complex
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2
Q

define efficacy

A

once a drug has bound to the receptor,

the ability to transduce a response and activate intracellular signaling pathways

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3
Q

affinity is shown by:
and
efficacy is shown by:

A

affinity is shown by: both agonists + antagonists

efficacy is shown by: agonist only

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4
Q

What are the 2 groups of cholinoceptors ?

A
  • Nicotinic

- Muscarinic

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5
Q

What are the 2 ways in which you can interfere with an ion channel linked receptor ?

A

a) block receptor (receptor blockade antagonists)
- -> prevents ion channels from opening
- -> causes total loss of autonomic function

b) block ion channel itself (ganglionic blocking drugs)

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6
Q

How do ganglion blocking drugs work?

A
  • Ganglion blockage drugs block the ion channel
  • prevents ions from moving through the channel pore
  • it interferes with both Para + Sympa action
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7
Q

How do ganglion blocking drugs work?

A
  • Ganglion blockage drugs block the ion channel
  • prevents ions from moving through the channel pore
  • it interferes with both Para + Sympa action
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8
Q

What is Use dependent block?

A
  • if more agonist = present at the receptor,
  • there is more opportunity for antagonists to block the channel so these drugs become more effective
  • i.e means that the drug is more effective when the channels are open
    note: this is an ‘incomplete block’ - slows it down
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9
Q

Which of the following effects would be observed at rest after treatment with a ganglion blocking drug?

a) Increased heart rate
b) Pupil constriction
c) Bronchodilation
d) Detrusor contraction
e) Increased gut motility

A

answer =

a) Increased heart rate
c) Bronchodilation

  • AT REST –> so opposite of that
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10
Q

what was hexamethonium previously used as?

why is it no longer used?

A
  • previously used as anti hypertensive
  • no longer used as side effect profile = v large
    note: more of a channel blocker
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11
Q

What are some uses of Trimetaphan?

is it long lasting or short acting?

A
  • used during surgery when controlled hypotension is needed
  • short acting

note: more of a receptor blocker

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12
Q

What effect does alpha bungarotoxin have on the body?

A
  • alpha bungarotoxin = snake venom
  • it is a nicotinic receptor blockade antagonist
  • targets skeletal muscle of the somatic nervous system
  • causing paralysis of skeletal muscle + diaphragm
  • leading to suffocation + death
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13
Q

In normal doses, atropine causes:

In normal doses, hyoscine:

in higher does both cause:

A

atropine
- little CNS effect

Hyoscine
- good sedative

high dose atropine = agitation

high dose hyoscine = CNS depression

  • -> different responses may be due to atropine being less M1 selective
  • so hyoscine = more effective on m1
  • also hyoscine = more lipid soluble than atropine
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14
Q

What is Tropicamide?

and what is its use

A

Tropicamide = Muscarinic receptor antagonist

  • acts on receptors in iris
  • causes pupil dilation –> useful for retinal examination
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15
Q

Why are muscarinic receptor antagonists good as an anesthetic premedication ?

A
  • causes airways to dilate (useful for gas mask + intubation)
  • dries throat –> reduces risk of aspiration
  • reduces secretion in the lungs (+ mouth + saliva)
  • removes parasympathetic effect on the heart (anesthetic reduced rate + contractility anyways –> so to reduce doubling effect of slowing down heart parasympathetic influence = removed)
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16
Q

other than as a sedative, why is hyoscine used as a patch for motion sickness?

A
  • neurological effect
  • muscarinic receptors = important in relaying info from inner ear –> vomiting centers
  • muscarinic receptor ANTAGONISTS reduce flow of info from inner ear labyrinth (periphery) –> brain
  • reducing nausea.

note: hyoscine patch interferes with the vomiting signal –> less nausea

17
Q

How do muscarinic receptor antagonists act as a treatment method for parkinson’s disease?

A
  • in parkinson’s nigrostrial dopamine neurons = lost
  • nigrostrial dopamine neurons (in basal ganglia) –> important in fine control of movement

NORMALLY: muscarinic receptors have inhibitory effect on dopamine signaling
- if person has parkinson’s, they have already LOST these neurones so we don’t want these inhibitory effect anymore

SO

  • antagonists take out M4 receptors
  • which causes inhibitory effect to be lost
  • and so remaining D1 dopamine neurons can fire at max rate

parkinson - u lose dopaminergic neurones

  • so d1 receptor stimulation is less effective
  • so fine control of movement is lost
  • drug –> enhances the D1 receptor
18
Q

How do muscarinic receptor antagonists act as a treatment method for asthma + COPD?

give an example

A
  • administered as an aerosol
  • aerosol = +vely charged
  • -> so doesn’t get out of lungs very well
  • so it is held localized in the lungs

e. g IPRATROPIUM BROMIDE –> removed effects of bronchoconstriction
- helps in obstructive airway diseases.

19
Q

How do muscarinic receptor antagonists act as a treatment method for Irritable Bowel Syndrome (IBS) ?

A
  • it knocks out parasympathetic effect in gut
  • and reduces smooth muscle contraction/gut motility/ gut secretions
  • relieves symptoms
20
Q

List unwanted side effects of muscarinic receptor antagonists

A
  • decreased sweating
  • reduced secretions (e.g saliva, mucous)
  • affects accommodation ability of colliery muscle (cycloplegia)
  • high dose: CNS agitation/restlessness/confusion
  • risk of poisoning

note: hot as hell
dry as bone
blind as a bat
mad as a hatter

21
Q

Describe the mechanism of botulinum toxin

A
  • NORMALLY: SNARE complex allows vesicles to fuse with memb + release ACh

BUT

  • Botulinum toxin binds to SNARE complex –> prevents release of ACh –> vesicle remains in nerve

–> very potent

22
Q

how is botulinum toxin used clinically?

A
  • botox = injected in the face to remove wrinkles

- locally paralyses skeletal muscle

23
Q

Why might nicotinic antagonists cause hypotension?

A
  • increase in HR
  • interference with vasoconstriction
  • so there is more vasodilation and TPR goes down –> hypotension
  • renin release decreases
  • -> hypotension
24
Q

What is the effect of nicotinic antagonists on exocrine secretions?

A
  • decrease in secretions
25
Q 
Which of the following drugs would you
administer to treat an atropine overdose?
a) Bethanechol
b) Ecothiopate
c) Hyoscine
d) Physostigmine
e) Pralidoxime
A

ANSWER: d) Physostigmine

technically both Ecothiopate + Physostigmine work
but b = irreversible (long + lasting effects) and usually you want a drug that is reversible

26
Q

How does physostigmine

used for atropine poisoning?

A
  • in atropine poisoning, you have are no. of atropine binding to muscarinic receptor
  • so you get muscarinic side effects
  • if you use physostigmine
  • which blocks acetyl cholinesterase reversibly
  • so Ach becomes dominant
  • and it outcompetes atropine
  • so normal function is restored
27
Q

Give two examples of ganglion blocking drugs

A
  • Hexamethonium

- Trimetaphan

28
Q

What are ganglionic blocking drugs also known as ?

A

Nicotinic receptor antagonists

29
Q

describe the characteristic of side effects of Trimetaphan

A
  • depends on whether SNS / PSN is dominant

eLCRS - 팜 (36 decks)

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