RESP - C. SAR AT BETA-ADRENORECEPTORS-COVERED

Question 1

what is an adrenoceptor

Answer 1

• receptor in the body that can bind to adrenaline
• adrenaline binds to all classes
• noradrenaline only binds to alpha

Question 2

adrenaline (adrenalin/epinephrine)

Answer 2

• R-stereoisomer
• hormone, neurotransmitter (fight or flight)
• agonist
• heart rate, blood vessel diameters, air passage diameter, metabolism
• treatment for anaphylaxis (epipen, Auvi-Q)
• mono-amine, ‘catecholamines’
• alpha- and beta-AR activation

Question 3

noradrenaline

Answer 3

• neurotransmitter (fight or flight)
• affects heart rate
• alpha-AR activation

Question 4

alpha1 and alpha2

Answer 4

alpha1:
- smooth muscle contraction via release of Ca2+ etc
- vasoconstriction in blood vessels

alpha2:
- inhibits insulin release
- inhibits NA release in brain and CNS
- contraction of sphincters in GIT

*phenylephrine is selective agonist for alpha-1 receptor

Question 5

beta1, beta2, beta3

Answer 5

beta1:
- increases heart rate, renin secretion from kidney etc

beta2:
- relaxes bronchi smooth muscles
- stimulates insulin release
- inhibits histamine release from mast cells

beta3:
- enhances lipolysis in adipose tissue

*isoprenaline is non-selective agonist

Question 6

how to make isoetharine more resistant to metabolism by COMT

Answer 6

• replace meta-OH with -CH2OH
• B2 agonist but short-acting as methylated by COMT to inactive form

Question 7

isoprenaline

Answer 7

B1 (heart) and B2 (bronchi)
mortality epidemic

• caused cardiac depression as well as relaxation of smooth muscle

Question 8

salbutamol (SABA)

Answer 8

B2 (bronchi)
R = active form
S = blocks metabolism of R (racemate will be cheaper and metabolism of R won’t occur)
t-butyl group produces selectivity for B2 receptors

Question 9

salmeterol (LABA)

Answer 9

• bulky N-substituent
• selective for B2 receptors due to bulkiness
• more lipophilic
• acts 2x longer than salbutamol due to bulkiness
• slower onset - prevention/management rather than relief

Question 10

fenoterol

Answer 10

• short-acting B2 agonist
• also stimulated B1 when used above recommended dose
• withdrawn due to mortality issues