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Y2 LCRS Pharm Fwong > SNS antagonists COPY > Flashcards

SNS antagonists COPY Flashcards

1
Q

What are the 2 main roles of alpha 1 adrenoceptors?

A

Vasoconstriction + GIT relaxation

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2
Q

What subtype of G protein are alpha 1 adrenoceptors linked to?

A

Gq

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3
Q

What are the 2 main roles of alpha 2 adrenoceptors?

A

Neg. feedback at presynaptic terminal

CNS actions

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4
Q

What subtype of G protein are alpha 2 adrenoceptors linked to?

A

Gi

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5
Q

What are the 2 main roles of beta 1 adrenoceptors?

A
  1. Increase HR and contractility

2. Increase renin release

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6
Q

What are the 2 main roles of beta 2 adrenoceptors?

A

Bronchodilation

Vasodilation

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7
Q

What is the main role of beta 3 receptors?

A

Lipolysis

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8
Q

Give an example of a selective alpha 1 antagonist

A

Prazosin

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9
Q

What is the main clinical use of alpha antagonists?

A

TPR decrease

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10
Q

Give an example of a non-selective alpha antagonist

A

Phentolamine

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11
Q

Where do non-selective antagonists act other than alpha receptors?

A

Baroreceptors

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12
Q

Difficult – why do alpha 2 receptors and baroreceptors reduce the effectiveness of phentolamine?

A

A2 blockade- loses negative feedback and so more NA released into synapse. NA competes with phentolamine for a1 blockade and eventually outcompetes phentolamine as NA conc goes up

Baroreceptor reflex triggered which causes heart to beat quicker and stronger whilst the phentolamine is dilating the vessels and this is not good for the heart. (Although TPR will have greater influence on overall BP, it is still not great for the heart )

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13
Q

What is the main side effect of phentolamine and why?

A

alpha receptors NORMALLY:
Decrease motility + tone, Sphincter contraction. ie decreases GIT activity

Blocking this = increased motility + tone and sphincter relaxation

= DIARRHOEA

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14
Q

Give 2 examples of selective beta 1 antagonists

A

Atenolol, nebivolol

Remember from coursework= atenolol is better than pindolol due to less reflex tachycardia because of its B1 selectivity

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15
Q

Clinical use of beta blockers?

A

Anti-hyertensives
Anti-arrhythmic
Angina
Glaucoma

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16
Q

Recall 6 possible side effects of beta receptor antagonism

A
  1. Bronchoconstriction (caution: asthma)
  2. Reduced Hepatic glucose release + masking symptoms of hypoglycaemia (caution: diabetics)
  3. Reduced SNS action on heart (caution: heart failure)
  4. Fatigue
  5. Cold extremities
  6. Bad dreams due to CNS effects
17
Q

Give 2 examples of non-selective beta antagonists

A

Propanolol

Carvedilol

18
Q

Recall the selectivity of carvedilol

A

Beta 1, beta 2, alpha 1

19
Q

Recall an advantage and a disadvantage of carvedilol use

A

Advantage: antagonises beta and alpha 1 receptors so pronounced effect on BP
Disadvantage: significant side effect profile

20
Q

Give an example of a false transmitter

A

methyldopa

21
Q

MOA of false transmitter

A

Methyldopa is basically an altered version of DOPA (physiological NA precursor). The alpha-methylnoradrenaline from methyldopa is similar to NA but a less powerful agonist for a1, b1 and b2 BUT a better agonist for a2. alpha methyl-NA gets released into synaptic cleft. After its reuptake via uptake 1, it is resistant to MAO-A metabolism hence builds up in presynaptic terminal and eventually reaches high enough concentration to displace NA in the vesicles and be released again back into the synapse

22
Q

Main effect of methyldopa

A

postural hypotension (theyre too good at what they do)

23
Q

How does the sympathetic nervous system worsen arrhythmias and therefore which class of drugs would you use ?

A

B1 receptor involved in
- HR and contractility
- facilitates AV conductance
Use beta blockers eg propanolol

24
Q

3 types of angina

A

stable - atherosclerosis
unstable - bad atherosclerosis leading to significant narrowing/rupture causing a thrombus
variable - narrowing is due to coronary artery vasospasm rather than atherosclerosis but can be associated with it

25
Q

Summarise how b blockers help with angina

A

reduce the demand on the heart (think of demand supply)

  1. reduce HR
  2. reduce contractility
26
Q

outline how b blockers can be used for glaucoma

A

B1 receptor drives Aqueous humour Production. Beta blockers Can block this and hence Reduce b1 stimulation and less
Aqueous humour production

Y2 LCRS Pharm Fwong (40 decks)

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