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- AAI; Chemistry > Adrenaline chemistry > Flashcards

Adrenaline chemistry Flashcards

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1
Q

What are adrenaline’s effects on the body and what family does it belong to?

A
  • Increases heart rate, blood vessel diameter, airway diameter and metabolism
  • Of the catecholamine family (mono-amine)
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2
Q

What is adrenaline?

A
  • A hormone/neurotransmitter

- Fight or flight response

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3
Q

How does noradrenaline differ from adrenaline and what effect does this have?

A

Noradrenaline (NT of the body) features a hydrogen bound to the amine instead of a methyl group in adrenaline.

This conveys much more specific action, activating α-adrenoceptors.

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4
Q

What are the steps in adrenaline biosynthesis and what enzymes are involved?

A 
- L-tyrosine (amino acid)
(tyrosine hydroxylase)
- L-DOPA (L-dihydroxyphenylalanine)
(DOPA decarboxylase)
(Aromatic L-amino acid decarboxylase)
- Dopamine
(Dopamine beta-hydroxylase)
- Noradrenaline
(Phenylethanolamine)
(N-methyltransferrase; transferring methyl onto amine instead of hydrogen)
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5
Q

What do α-1 adrenoceptors activate?

A 
Smooth muscle contraction 
(often vasoconstriction in blood vessels e.g. 
-skin, 
-GI system, 
-renal artery, 
-brain) via release of Ca2+ etc.

(vascular smooth muscle contraction)

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6
Q

What do α-2 adrenoceptors activate?

A
  • Inhibits insulin release
  • Inhibits noradrenaline release in brain and CNS
  • Contraction of sphincters in GI tract.

(vascular smooth muscle contraction, pre-junctional regulation of NA release)

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7
Q

What do β-1 adrenoceptors activate?

A
  • Increase heart rate
  • Renin (an angiotensinogenase) secretion from kidney

(SA node and ventricles in heart; rate and force of contraction)

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8
Q

What do β-2 adrenoceptors activate?

A
  • Relaxes bronchi
  • Stimulates insulin release
  • Inhibits histamine release from mast cells (allergies)

(airway smooth muscle relaxation)

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9
Q

What do β-3 adrenoceptors activate?

A
  • Enhances lyopolysis in adipose (fatty) tissue etc

skeletal muscle, adipose tissue

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10
Q

Is adrenaline selective?

A

No; it is an agonist for both α and β receptors.

noradrenaline is agonist for just α

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11
Q

What structural change from adrenaline brings about α-selectivity? (and name a subsequent drug)

A
  • Removing the bottom -OH group on the aromatic ring,

e. g. phenylephrine.

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12
Q

What structural change from adrenaline brings about β-selectivity? (and name a subsequent drug)

A
  • Amine substitution (the 2 hydrogens from initial methyl group and both replaced with more methyl groups)
    e. g. isoprenaline
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13
Q

What structural change from adrenaline brings about short-lasting β-2 selectivity? (and name a subsequent drug)

A
  • Substitution of hydrogen between OH and N for butyl group

e. g. isoetharine

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14
Q

What structural change from adrenaline brings about longer-lasting β-2 selectivity? (and name a subsequent drug)

A
  • Addition of CH2 between top -OH on aromatic ring and the aromatic ring
  • Bulkier N-substituent (more lipophilic as a result; bigger R-group attached favours β-2 selectivity; T-butyl group in…)
    e. g. salbutamol
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15
Q

Why is the β-2 selective agonist isoetharine so short-lasting?

A
  • Taken up by tissues and methylated by COMT (Catechol-O-methyltransferase) to inactive form
    (thus replacing -OH with CH2OH yields greater resistance to metabolism)
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16
Q

Why is salbutamol #preferable to isoprenaline to treat bronchoconstriction?

A
  • Salbutamol acts just on the β-2 adrenoceptors
  • Isoprenaline acts on β-1 and β-2; gave rise to a mortality epidemic when small doses given to hypoxemic dogs (asthma sufferers would have low O2 too…) giving rise to fatal cardiac depression.
  • Salbutamol is 7 times less potent than isoprenaline in raising heart rate in humans.
17
Q

Why was the short-acting β-2 agonist fenoterol withdrawn from the market?

A
  • Short-acting β-2 agonist also stimulated β-1 when used above recommended dose (possible abuse of dose during bronchoconstriction)
  • Thus withdrawn from market (NZ) due to mortality issues
18
Q

Why is salbutamol given as a racemic mixture?

A
  • R-stereoisomer is active form
  • However S-form actually blocks metabolism of R-form thus lasting longer
  • Thus giving S with R enhances activity of R
19
Q

What are the steps of Salbutamol synthesis?

A
  • Fries re-arrangement
  • Esterification
  • Bromination
  • Nucleophilic substitution
  • Reduction
  • Hydrogenolysis
20
Q

How does Salmeterol achieve its long-acting status?

A
  • Bulky N-substituent (alkyl tail w/ester/benzene ring)
  • Thus more lipophilic (hangs on for longer?)
  • Acts for 2x longer than salbumatom

- AAI; Chemistry (2 decks)

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