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Clinically Based Concepts > module 3: first pass, phase i, and phase ii metabolism > Flashcards

module 3: first pass, phase i, and phase ii metabolism Flashcards

1
Q

where is metabolism occurring?

A

liver -> hepatocytes -> smooth ER

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2
Q

what is the path of blood supply to the liver during general metabolism?

A

liver -> inferior vena cava -> heart -> aorta -> celiac artery -> common hepatic artery -> liver

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3
Q

what is first pass metabolism?

A

metabolism of a drug before it reaches the systemic circulation

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4
Q

what are the two blood supplies to the liver?

A

hepatic artery
hepatic portal vein

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5
Q

list the pathway of a pill being swallowed

A

intestines -> hepatic portal vein -> liver

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6
Q

true or false: drugs given by mouth are not able to get to the rest of the body before they get metabolized and are subject to first pass metabolism

A

true

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7
Q

true or false: rectal administration of a drug is subject to first pass metabolism

A

true

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8
Q

list the pathway of a drug given rectally

A

rectum -> hepatic portal vein -> liver

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9
Q

what are some administration pathways that won’t undergo first pass metabolism?

A

sublingual
IM

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10
Q

what is bioavailability?

A

fraction of a drug given that reaches systemic circulation

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11
Q

true or false: drugs with low bioavailability do not undergo first pass metabolism

A

false

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12
Q

the intestines contain enzymes that help metabolize drugs and ________ bioavailability

A

reduce

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13
Q

less drug absorbed means ________ plasma concentration

A

decreasing

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14
Q

true or false: drugs that undergo first pass metabolism have decreased plasma

A

true

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15
Q

metabolizing an active drug or molecule does what to it?

A

inactivates it

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16
Q

what happens when the body thinks a drug is toxic?

A

metabolizes drug to make it non-toxic

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17
Q

what is the drug called when given in its inactive form and becomes active once metabolized by the body?

A

pro drug

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18
Q

whats an example of a pro drug turning into an active drug?

A

codeine -> morphine

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19
Q

what is an example of a non toxic drug metabolizing to toxic?

A

acetaminophen -> hepatotoxic metabolites

20
Q

what happens when a lipid drug becomes metabolized?

A

becomes water soluble

21
Q

excretion is easiest when in what form?

A

water soluble

22
Q

what enzymes do phase I use?

A

CYP 450, oxidases (oxidation reactions, unmask O2)

23
Q

what does phase II use to metabolize?

A

conjugation reactions

24
Q

what is the function of oxidases?

A

to unmask or introduce polar groups (-OHs, -Os) on the drug

25
Q

what does cytochrome p450 do?

A

heme-containing enzymes that bind O2 and CO

25
Q

what does cytochrome p450 do?

A

heme-containing enzymes that bind O2 and CO

26
Q

when oxygen binds to the drug and water is also formed, where do the hydrogens come from?

A

NADPH

27
Q

where does NADPH come from?

A

by product from G-6-P—–>G-PG (pentose phosphate shunt)

28
Q

how does NADPH act as a reducing agent?

A

it causes other molecules to get reduced and gain an electron and then as a result loses an electron, becoming oxidized which forms NADP+

29
Q

what is an example of a non-p450 phase I reaction enzyme?

A

alcohol dehydrogenase

30
Q

what is the purpose of alcohol dehydrogenase?

A

breaks down alcohol and takes it to form acetaldehyde (later broken down into acetate)

31
Q

what are the first and second most common cytochrome p450 enzymes?

A

CYP 3A4 and CYP 2D6

32
Q

explain the breakdown of the name CYP 3A4

A

3: family of drug
A: subfamily of enzyme
4: isozyme

33
Q

what type of enzyme does phase II metabolism use and why?

A

transferases to attach small endogenous polar molecules to a drug (to make more water soluble)

34
Q

what are examples of polar molecules added to a drug through phase II metabolism?

A

glucuronate
glutathione
sulfate
acetate

35
Q

what kind of reactions does phase II use?

A

conjugation

36
Q

what enzyme would be used to add acetyl to a drug?

A

N-acetyltransferase

37
Q

what is the purpose of adding an acetyl group to a histone?

A

increase gene transcription

38
Q

what are the most common conjugation reactions?

A

glucuronidation (most common)
sulfation
acetylation

39
Q

95% of tylenol is metabolized by _________ enzymes that form a non-toxic metabolite

A

phase II

40
Q

which phase I enzyme metabolizes over 50% of available drugs?

A

CYP 3A4

41
Q

which phase I enzyme is famous for polymorphisms (codeine)?

A

CYP 2D6

42
Q

what does the phase II enzyme UGT stand for and is responsible for what reaction?

A

UDP-glucuronosyltransferase —–> glucuronidation

43
Q

what does the phase II enzyme GST stand for and is responsible for what reaction?

A

glutathione-S- transferase ——> glutathione conjugation

44
Q

what does the phase II enzyme NAT stand for and is responsible for what reaction?

A

N-acetyltransferase ——> acetylation

45
Q

what does the phase II enzyme SULT stand for and is responsible for what reaction?

A

sulfotransferase —–> sulfation

Clinically Based Concepts (10 decks)

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