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Y2 Pharmacology and Therapeutics > Cholinoreceptor antagonists > Flashcards

Cholinoreceptor antagonists Flashcards

1
Q

What is the relationship between agonists, antagonists and affinity

A

agonists and antagonists possess affinity

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2
Q

What is the relationship between agonists, antagonists and efficacy

A

Only agonists possess efficacy

activate the receptor to generate a response

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3
Q

What are nicotinic receptor antagonists

A

ganglion blocking drugs

Blocks ligand-dating ion channels or receptors

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4
Q

Give 2 examples of nicotinic receptor antagonists and what are their clinical uses

A

hexamethonium - 1st anti-hypertensive (nictonic receptor)

trimetaphan - hypotension during surgery (LG-ion channel)

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5
Q

Why do ganglion blocking drugs cause hypotension

A

Blocks the sympathetic system which increases renin secretion in the kidney and causes constriction in the blood vessels -> hypotension

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6
Q

What are the overall effects of ganglion blocking drugs

A

Hypotension (CVS)

Overall relaxation (pupil dilation, decrease GI tone, bladder dysfunction, bronchodilation
Exocrine secretions decrease
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7
Q

What is a natural nicotinic receptor anrtagonist

A

alpha-bungarotoxin from the common krait snake which strongly covalently bonds to nicotinic receptor (affects somatic nervous system -> skeletal muscle affected)

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8
Q

Give 2 examples of muscarinic receptor antagonists

A

Atropa belladone -> atropine

Hyoscymus niger -> Hyoscine

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9
Q

What are the effects of atropine on the CNS

A

Normal dose - little effect

toxic - mild restelessness, agitation

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10
Q

What are the effects of hycosine on the CNS

A

normal dose - sedation, amnesia

Toxic dose - CNS depression or paradoxical CNS excitation (associated with pain)

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11
Q

Which drug permeates into the CNS greater: atropine or hycosine

A

Hycosine

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12
Q

Give an example of a msucarinic receptor antagonists used clinically for the eye

A

Tropicamide
Examination of the retina
Blocks the muscarinic receptor, paralysing the ciliary muscle and pupil causing dilation to widen the view of the retina

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13
Q

What are the effects of the muscarinic receptor antagonists that are useful for anaesthetic premedication

A

Blocks constriction of trachea and bronchioles
Blocks copious watery secretion from the salivary glands
Blocks and decreases heart rate and contractility
Sedation

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14
Q

How are muscarinic receptor antagonists used neurologically

A

Hycosine patch

Motion sickness

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15
Q

How are muscarinic receptor antagonists used in Parkinson’s disease

A

cholinergic/dopaminergic balance in basal ganglia

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16
Q

How are muscarinic receptors antagonists used in respiratory diseases

A

Asthma/obstructive airway disease

e.g. ipratropium bromide (+atropine)

17
Q

How are muscarinic receptor antagonists used in GI diseases

A

Irritable bowel syndrome

M3 receptor antagonists to reduce side effects

18
Q

What are the unwanted effects of muscarinic receptor antagonists

A

Hot - decreased sweating and thermoregulation
Dry - Decrease secretions
Blind - cyclopegia
Mad - CNS disturbance

19
Q

Describe LG-ion channels

A

No affinity
Use-dependent
Incomplete blocking/antagonism

20
Q

What are the kinds of effects you can achieve from a ganglion blocking drug

A

Increased heart rate

Bronchodilation

21
Q

How do ganglia blocking drugs cause hypotension

A

Dilation of blood vessels (reduced TPR)

Stops renin secretion (less aldosterone, less reabsorption)

22
Q

What are the clinical uses of hexamethonium and trimetaphan

A

Hexamethonium -> 1st Anti-hypertensive

Trimetaphan-> Hypotension during surgery (short acting)

23
Q

Which physiological responses are influenced by muscarinic receptor antagonists

A

Pupil and ciliary muscle contraction
Bronchiole constriction
Saliva production
Increased GI motility, tone and secretion
Contraction of depressor, relaxation of trigone and sphincter
Sweating

24
Q

Why is ipratropium used clinically despite its structure being similar to atropine

A

Charged group added so therefore more polar

Less likely to diffuse through lipid membranes and hence the lungs

25
Q

Which drugs could you administer to treat an atropine overdose

A

Bethanechol
Physostigmine

*ecothiopate would work but is irreversible and would be dangerous

26
Q

Why is physostigmine used to treat atropine overdose

A

Is an anti-acetylcholinesterase and therefore increases acetylcholine conc. in the synapse, making it a better competitive substrate for the receptor

27
Q

What is the botulinum toxin

A

Parasympatholytics

Prevents acetylcholine exocytosis

Y2 Pharmacology and Therapeutics (34 decks)

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