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Pharmacology & Therapeutics Y2 > Drug Metabolism > Flashcards

Drug Metabolism Flashcards

1
Q

What is a xenobiotic

A

a substance found within an organism that is not usually found within the organism

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2
Q

what is the normal polarity of a xenobiotic

A

non-polar

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3
Q

What do we do to xenobiotics to excrete them and why

A

we manipulate them to become polar so they can be readily excreted

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4
Q

where does metabolic transformation primarily occur

A

in the liver

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5
Q

what is first pass metabolism

A

the amount of a substance that is metabolised by the liver the first time it enters the liver from the gut

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6
Q

What types of reaction can you get in phase I of metabolic transformations (3)

A

Oxidation, reduction and hydrolysis

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7
Q

what types of reactions can you get in phase II of metabolic tranformationa

A

Glucoronidation, amino acid or glutathione conjugation, sulphation, acetylation and methylation

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8
Q

which phase of metabolic change changes the polarity of a drug

A

Phase II

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9
Q

Are both phases compulsory? If not which one is

A

Neither are, sometimes only phase I or sometimes only phase II

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10
Q

In cytochrome P450 mediated oxidation, if the drug is:
RH + NADPH + O2 + H+

What’s the oxidised drug?

A

ROH + NADP+ + H2O

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11
Q

In cytochrome P450 mediated oxidation, if the oxidised drug is:
ROH + NADP+ + H2O

What’s the reactants drug?

A

RH + NADPH + O2 + H+

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12
Q

What does hydrolysis do in phase I

A

Unmasks 2 functional groups

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13
Q

What do the functional groups revealed in phase I do in phase II

A

serve as attachment points for phase II reactions

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14
Q

When is cytochrome P450 used?

A

Phase I of metabolic transformations

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15
Q

What does phase I usually do to drugs? When is the exception?

A

Inactivates them, in the case of prodrugs can activate them

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16
Q

Drug binds to CYP450, what happens next

A

Drug binds to the iron in the catalytic site and a NADPH donates an electron. This reduces Fe3+ to Fe2+. Oxygen then binds to CYP450. The Fe2+ reduces oxygen, and then Fe3+ is reduced again by NADPH and this again reduces oxygen making it very unstable. The drug is then hydroxylated by one of the O2’s and we lose the other oxygen as water by picking up 2 protons.

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17
Q

What is used during CYP450 oxidation

A

2 NADPH’s for their electrons, 2 hydrogens and an O2

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18
Q

What does oxidation do to N-methyl or O-methyl groups

A

It removes HCHO (formaldehyde), AKA demethylation

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19
Q

What is N-oxidation

A

Donating the lone pair of electrons on nitrogen to an oxygen

20
Q

Which oxidation uses different enzymes rather than CYP450

A

N-oxidation and alcohol oxidation, which uses alcohol dehydrogenase

21
Q

What type of enzyme does reductions

A

Reductases

22
Q

Where do the majority of our reductase enzymes come from

A

bacteria in the GI tract

23
Q

Which molecules does hydrolysis occur to

A

Esters and amides

24
Q

What enzyme does glucoronidation

A

Glucoronyl transferase

25
Q

What enzyme does acetylation

A

acetyl transferase

26
Q

What enzyme does amino acid conjugation

A

Acyl transferase

27
Q

What enzyme does methylation

A

Methyl transferase

28
Q

What enzyme does sulphation

A

Sulphotransferase

29
Q

What enzyme does glutathione conjugation

A

Glutathione-S-transferase

30
Q

What drug is pharmacologically active after conjugation

A

Morphine, morphine glucuronide is still active

31
Q

why does conjugation make drugs easier to excrete

A

the huge polar group added to it makes it less lipid soluble

32
Q

What is the main defence mechanism of the body to get rid of harmful chemicals (free radicals and electrophiles)

A

Glutathione

33
Q

What is the conjugating agent for glucuronidation

A

UDP-glucoronic acid

34
Q

What is the conjugating agent for acetylation

A

Acetyl CoA

35
Q

What is the conjugating agent for amino acid conjugation

A

Glycine, glutamine, taurine

36
Q

What is the conjugating agent for methylation

A

S-adenosyl methionine

37
Q

What is the conjugating agent for sulphation

A

3’-phosphoadenosine-5’-phosphosulphate

38
Q

What is the conjugating agent for glutathione conjugation

A

Glutathione

39
Q

Which type of phase II reactions occurs the most

A

Glucuronidation

40
Q

What elements does acetylation and methylation target (3)

A

N, O, and S

41
Q

What is the target functional group for glucuronidation (4)

A

OH, COOH, NH2, SH

42
Q

What is the target functional group for acetylation (2)

A

OH, NH2

43
Q

What is the target functional group for amino acid conjugation

A

COOH

44
Q

What is the target functional group for methylation (2)

A

OH, NH2

45
Q

What is the target functional group for sulphation (2)

A

OH, NH2

46
Q

What is the target functional group for glutathione conjugation

A

electrophiles

Pharmacology & Therapeutics Y2 (10 decks)

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