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MPharm 2 - PH2114 > Phase 2 Metabolism > Flashcards

Phase 2 Metabolism Flashcards

1
Q

How are conjugated polar molecules eliminated from the body?

A

Urine

Bile

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2
Q

Give some examples of conjugation reactions that take place during phase II metabolism

A 
Glucuronidation
Sulphation
Amino acids
- glutathione
- glycine
- glutamine
Acetylation
Methylation
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3
Q

Which groups are commonly conjugated by glucuronidation reactions during phase II metabolism?

A
  • OH
  • COOH
  • NH2
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4
Q

Which groups are rarely conjugated by glucuronidation reactions during phase II metabolism?

A
  • NR2
  • SH
  • CH
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5
Q

What is the source for glucuronidation?

A

Uridine-5’diphosph-alpha-D-glucuronic acid

- UDPGA

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6
Q

Which enzymes are responsible for glucuronidation reactions in phase II metabolism?

A

UDP-glucuronosyl-transferase

- UDPGT

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7
Q

How is aspirin metabolised during phase II metabolism?

A

Glucuronidation

  • ether
  • ester
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8
Q

What does phase 2 metabolism do ?

A

Phase 2 metabolism links the the drug to still more polar molecules to render them even more easy to excrete

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9
Q

how much more ether glucuronide is formed compared to ester glucuronide during aspirin metabolism?

A

Twice as much

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10
Q

Which groups are conjugated by sulphation reactions during phase II metabolism?

A
  • OH

- NH2

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11
Q

What is the source for sulphation?

A

3’phosphoadenosine-5’-phosphosulphate

- PAPS

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12
Q

Which enzyme is responsible for sulphation reactions in phase II metabolism?

A

Sulphotransferase

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13
Q

How is paracetamol metabolised during phase II metabolism?

A

Glucuronidation

Sulphation

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14
Q

What proportion are paracetamol-glucuronide and paracetamol-sulphate found in urine following phase II metabolism?

A

Roughly equal amounts after normal doses of paracetamol

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15
Q

Which groups are conjugated with glutathione (GSH)?

A
  • Ar-X
  • aryl halides
  • arene oxide
  • epoxide
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16
Q

What is glutathione (GSH)?

A

Tri-peptide structure consisting of

  • glycine
  • cysteine
  • glutamic acid
17
Q

How is paracetamol converted to NAPQI during phase II metabolism?

A

Reduction

18
Q

What is produced when NAPQI is conjugated with glutathione?

A

Paracetamol-mercapturic acid

19
Q

How is NAPQI formed?

A

Probable from an N-hydroxy metabolite

20
Q

How is toxic NAPQI metabolised during phase II metabolism?

A

GSH conjugation prevents toxicity of these oxidative metabolites after normal doses
- mechanism is swamped after overdose

21
Q

Which groups are conjugated by acetylation during phase II metabolism?

A
  • OH

- NH2

22
Q

Which enzyme is responsible for acetylation during phase II metabolism?

A

Acetyl co-enzyme A

23
Q

What causes variations in some acetyl transferases?

A

Genetic variation

  • fast and slow acetylators
  • frequency varies with race
24
Q

What percentage of caucasians are slow acetylators?

A

60%

25
Q

What percentage of eskimos are fast acetylators?

A

95%

26
Q

Which groups are conjugated by methylation during phase II metabolism?

A

-OH
-NH2
-SH
heterocyclic N

27
Q

What is the source of methylation during phase II metabolism?

A

S-Adenosyl-L-methionine (SAM)

28
Q

When does O-methylation occur most commonly during phase II metabolism?

A

With catechols with metabolism at the meta position

- COMT enzyme

29
Q

How is dopamine metabolised?

A 
Monoamine oxidase (MOA) or aldehyde dehydrogenase
then COMT enzyme

OR

COMT enzyme then aldehyde dehydrogenase

Produces homovanillic acid

30
Q

What is catechol?

A

Aromatic ring with 2 OH groups next to each other

31
Q

What effect does grapefruit juice have on CYP3A4 enzymes?

A

Grapefruit juice inhibits the enzyme from metabolic processes -> higher levels of drug in blood -> more side effects

MPharm 2 - PH2114 (32 decks)

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