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notes to flashcards year 2 - LCRS1 > SNS agonists > Flashcards

SNS agonists Flashcards

1
Q

how do directly acting sympathomimetics work?

A
  • mimic actions of NA/A by binidng to and stimulating adrenoreceptors
  • used principally for their actions in CVS, eyes, lungs
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2
Q

what do the adrenoreceptors in the eye do?

A
  • ALPHA 1: contraction of iris radial muscle

- BETA: aqueous humour proudction by ciliary body

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3
Q

what do the adrenoreceptors do in the trachea and bronchioles?

A
  • BETA 2: dilate
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4
Q

what do the adrenoreceptors in the liver do?

A
  • ALPHA 1: glycogenolysis

- BETA 2: gluconeogenesis

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5
Q

what do the adrenoreceptors in the adipose tissue do?

A
  • ALPHA 1, BETA 1: lipoylsis
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6
Q

what do adrenoreceptors do in the kidney?

A
  • BETA 1: inc. renin release
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7
Q

what do adrenoreceptors do in the urinary bladder?

A
  • BETA 2: relaxes detrusor

- ALPHA 1: constricts trigone and sphincter

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8
Q

what do adrenoreceptors do in the ureter?

A
  • ALPHA 1: inc. motility and tone
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9
Q

what do adrenoreceptors do in male genitalia?

A
  • ALPHA 1: stimulates ejaculation
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10
Q

what do adrenoreceptors do in the lacrimal glands?

A
  • ALPHA 1: stimulates tears
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11
Q

what do adrenoreceptors do in salivary glands?

A

ALPHA/BETA: thick viscid secretion

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12
Q

what do adrenoreceptors do in heart?

A

BETA 1: inc. rate and contractility

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13
Q

what do adrenoreceptors do in GIT?

A

ALPHA/BETA: dec. muscle motility and tone, contraction of sphincters

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14
Q

what do adrenoreceptors do in female genitalia?

A
  • BETA 2: relaxation of uterus
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15
Q

what do adrenoreceptors do in blood vessels?

A
  • BETA 2: skeletal muscle blood vessel dilation

- ALPHA 1: skin, mucus membranes, splanchnic are, abdo viscera, salivary gland bloos vessels construction

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16
Q

what is the noradrenaline selectivity?

A
  • sensitive to alpha

- alpha 1 = alpha 2 > beta 1 = beta 2

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17
Q

what is the adrenaline selectivity?

A
  • sensitive to beta

- beta 1 = beta 2 > alpha 1 = alpha 2

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18
Q

where is NA synthesised? A?

A

NA in nerve terminals

A in adrenal medulla

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19
Q

what is the -ve feedback on NE?

A

NE binding to prejunctional alpha 2 adrenoceptors negatively feedbacks on NE exosytosis

20
Q

name 6 directly acting SNS agonists and what they are selective for?

A
  1. adrenaline: non selective
  2. phenylephrine: alpha 1 selective
  3. clonidine: alpha 2 selective
  4. isoprenaline: beta selective
  5. dobutamine: beta 1 selective
  6. salbutamol: beta 2 selective
21
Q

how is adrenaline used in the treatment of anaphylaxis?

A
  • Adrenaline non selective
    management of:
  • airways: beta 2 = bronchodilation
  • tachycardia: beta 1 = reduced chronotropic and ionotropic effect
  • peripheral vasodilation: alpha 1 = vasoconstriction
  • suppression of mediator reelease
22
Q

why is adrenaline used in COPD management?

A 
- asthma
management of:
- airways, breathing: beta 2 = bronchodilation
- suppression of mediator release
- selective beta 2 agonsist preferable
23
Q

why is adrenaline used in glaucoma management?

A
  • inc. IOP
  • vasoconstriction of ocular blood vessels restricts blood flow so production of aqueous humour
  • ALPHA 1: vasoconstriction, dec. in IOP
24
Q

what are some other uses of adrenaline?

A
  • cardiogenic shock (beta 1 actions)
  • spinal anaesthesia (maintain BP)
  • local anaesthesia (prolong duration of action using alpha 1)
25
what are the unwanted actions of adrenaline?
- secretions: reduced and thickened - CVS: tachycardia, palpitations, arrhythmia, cold extremities, hypertension - skeletal muscle: tremor
26
what is the selectivity of phenylephrine?
most selective to least selective alpha 1 alpha 2 beta 1/2
27
what is the difference between adrenaline and phenylephrine?
- molecularly similar to adrenaline | - but resistance to COMT (but not MAO)
28
what are the clinical uses of phenylephrine?
- vasoconstriction - mydriasis - dilation - nasal decongestant via vasoconstriction
29
what is the selectivity of clonidine?
most selective to least selective alpha 2 alpha 1 beta 1/2
30
where does clonidine act?
mainly on prejunctional neuronal alpha2-receptor to inhibits NA release
31
what are the clinical uses of clonidine?
- treatment of hypertension and migraine - reduces sympathetic tone (alpha 2 mediated presynaptic inhibition of NA release, central brainstem action within baroreceptor to reduce sympathetic outflow)
32
what is the selectivity of isoprenaline?
beta 1/2 >> alpha 1/2
33
what is the structure of isoprenaline?
- molecularly similar to adrenaline - less susceptible to uptake 1 and MAO breakdown - fast plasms half life of 2 hrs
34
what are the clinical uses of isoprenaline?
- cardiogenic shock - acute HF - MI - CAUTION: beta 2 stimulaiton in VSM in skeletal muscle triggers a fall in venous BP, trigger reflex tachycardia via BR stimulation
35
what is the selectivity of dobutamine?
beta 1>> beta 2 >>> alpha 1/2
36
describe the pharmacokinetics of dobutamine?
admin by IV infusion very short half life of 2 mins rapidly metabolsied by COMT
37
what are the uses of dobutamine?
- cardiogenic shock | - lacks isoprenaline's reflec tachycardia
38
what is the selectivity of salbutamol?
beta 2 >> beta 1 >>> alpha 1/2
39
what is the structure of salbutamol?
synthetic catecholamine | resistance to COMT and MAO
40
what are the clinical uses?
- treatment of asthma (beta 2 relaxation of SM, inhibition of release of bronchoconstriction substances) - treatment of threatened premature labour (beta 2 relaxation of SM)
41
what are the side effects of salbutamol?
- reflex tachycardia - tremor - blood sugar dysregulation
42
name an indirectly acting SNS agonist. what is it's MoA?
- cocaine | - uptake 1 blocker
43
what are the CNS effects of cocaine?
low doses: euphoria, excitement, inc, motor activity | high doses: activation of CTZ, CNS depression, resp failure, convulsions, death
44
what are the CVS effects of cocaine?
low doses: tachycardia, vasoconstriction, raised BP | high doses: VF and cardiac arrest
45
what is tyramine? what is the problem with it?
- false neurotransmitter | - usually not a problem when the normal mechanisms for degradation are in place
46
what happens when there is inhibited MAO?
- tyramine admin can compete with any MAO left | - lead to a massive hypertensive crisis when NA build up is more than usual
47
describe the actions of tyramine
1. weak action at the receptors for NA 2. weak inhibitory effect on the uptake 1 3. displaces NA form vesicles 4. competes for MAO breakdown so less breakdown of NA 5. leakage of NA out of vesicles

notes to flashcards year 2 - LCRS1 (58 decks)

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