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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
Q

what are the unwanted actions of adrenaline?

A
  • secretions: reduced and thickened
  • CVS: tachycardia, palpitations, arrhythmia, cold extremities, hypertension
  • skeletal muscle: tremor
26
Q

what is the selectivity of phenylephrine?

A

most selective to least selective
alpha 1
alpha 2
beta 1/2

27
Q

what is the difference between adrenaline and phenylephrine?

A
  • molecularly similar to adrenaline

- but resistance to COMT (but not MAO)

28
Q

what are the clinical uses of phenylephrine?

A
  • vasoconstriction
  • mydriasis - dilation
  • nasal decongestant via vasoconstriction
29
Q

what is the selectivity of clonidine?

A

most selective to least selective
alpha 2
alpha 1
beta 1/2

30
Q

where does clonidine act?

A

mainly on prejunctional neuronal alpha2-receptor to inhibits NA release

31
Q

what are the clinical uses of clonidine?

A
  • 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
Q

what is the selectivity of isoprenaline?

A

beta 1/2&raquo_space; alpha 1/2

33
Q

what is the structure of isoprenaline?

A
  • molecularly similar to adrenaline
  • less susceptible to uptake 1 and MAO breakdown
  • fast plasms half life of 2 hrs
34
Q

what are the clinical uses of isoprenaline?

A
  • 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
Q

what is the selectivity of dobutamine?

A

beta 1» beta 2&raquo_space;> alpha 1/2

36
Q

describe the pharmacokinetics of dobutamine?

A

admin by IV infusion
very short half life of 2 mins
rapidly metabolsied by COMT

37
Q

what are the uses of dobutamine?

A
  • cardiogenic shock

- lacks isoprenaline’s reflec tachycardia

38
Q

what is the selectivity of salbutamol?

A

beta 2&raquo_space; beta 1&raquo_space;> alpha 1/2

39
Q

what is the structure of salbutamol?

A

synthetic catecholamine

resistance to COMT and MAO

40
Q

what are the clinical uses?

A
  • 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
Q

what are the side effects of salbutamol?

A
  • reflex tachycardia
  • tremor
  • blood sugar dysregulation
42
Q

name an indirectly acting SNS agonist. what is it’s MoA?

A
  • cocaine

- uptake 1 blocker

43
Q

what are the CNS effects of cocaine?

A

low doses: euphoria, excitement, inc, motor activity

high doses: activation of CTZ, CNS depression, resp failure, convulsions, death

44
Q

what are the CVS effects of cocaine?

A

low doses: tachycardia, vasoconstriction, raised BP

high doses: VF and cardiac arrest

45
Q

what is tyramine? what is the problem with it?

A
  • false neurotransmitter

- usually not a problem when the normal mechanisms for degradation are in place

46
Q

what happens when there is inhibited MAO?

A
  • tyramine admin can compete with any MAO left

- lead to a massive hypertensive crisis when NA build up is more than usual

47
Q

describe the actions of tyramine

A
  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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