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Nursing Pharmacology > Module 4 > Flashcards

Module 4 Flashcards

1
Q

Enzyme-mediated alteration of a drug’s structure

A

Metabolism

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2
Q

What are the different sites of drug metabolism?

A

Liver, intestine, stomach, kidney, intestinal bacteria

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3
Q

What is another term for metabolism?

A

biotransformation

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4
Q

What is the primary site of drug metabolism?

A

The liver

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5
Q

What are some common exogenous toxins?

A

Meat, wine/alcohol, cigarettes, coffee, drugs, vegetables

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6
Q

What are the different therapeutic consequences of drug metabolism?

A 
Increase water solubility of drugs to promote their excretion
Inactivate drugs
Increase drug effectiveness
Activate pro-drugs
Increase drug toxicity
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7
Q

What are some essential endogenous molecules provided by metabolism?

A

Vitamin D, bile acids, cholesterol, steroids, bilirubin

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8
Q

In most clinical situations, drug metabolism follows ____ order kinetics

A

first

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9
Q

Describe first order kinetics.

A

There is more enzyme than drug; therefore drug metabolism is directly proportional to the concentration of free drug

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10
Q

In first order kinetics, a constant _______ of drug is metabolized per unit time.

A

fraction

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11
Q

Describe zero order kinetics.

A

Plasma drug concentration > enzymes

Drug metabolism is constant over time

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12
Q

In zero order kinetics, a constant ________ of drug is metabolized per unit time.

A

amount

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13
Q

What is the best example of zero order kinetics?

A

Ethanol

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14
Q

In this metabolism kinetics, drug metabolism is independent of drug concentration.

A

Zero order

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15
Q

Where can first pass metabolism occur?

A

Hepatocytes in the liver
intestinal enterocytes
Stomach
Intestinal bacteria

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16
Q

What is the result of 1st pass metabolism?

A

A decreased amount of parent drug that enters the systemic circulation

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17
Q

What is an example of first pass metabolism in the stomach?

A

Alcohol –> Alcohol DH –> acetaldehyde

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18
Q

High ER drugs

  • have _____ oral bioavailability (-%)
  • PO does are usually ______ than IV doses
  • _____ change sin hepatic enzyme activity produce _______ changes in bioavailability
  • ______ susceptible to drug-drug interactions
A

low - 1-20%
higher (much)
small, large
very

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19
Q

Low ER drugs

  • have _____ oral bioavailability
  • PO doses are ______ to IV doses
  • ______ changes in hepatic enzyme activity have _______ effect on bioavailability
  • __ ______ susceptible to drug-drug interactions
  • Take ______ passes through the liver via the systemic circulation before they are completely metabolism
A 
high
similar
small, little
not very
many
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20
Q

What are the two phases of drug metabolism?

A

Phase I and Phase II

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21
Q

Phase I metabolism
- Convert _______ drugs to more ______ molecules by ________ or ________ polar functional groups such as ______ or ______

A

lipophilic, polar, introducing or unmasking

hydroxyl, amines

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22
Q

What are the different types of reactions in phase I metabolism?

A

Hydrolysis, oxidation, reduction

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23
Q

Phase I metabolism is mediate by what enzymes?

A

Cytochrome p450 enzymes (main), esterases, dehydrogenases

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24
Q

Describe the activity of the resulting metabolites of phase I metabolism.

A

More active, less active or equally as active as the parent drug

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25
Q

Phase II metabolism

- Increases the _______ of ________ drugs by _______ reactions

A

polarity, lipophilic, conjugation

26
Q

What are different conjugates of phase II metabolic reactions?

A

Glucuronic acid, sulfate, acetate or amino acids

27
Q

Describe the activity of metabolites of phase II metabolism.

A

Less active than the parent drug - except morphine-6-glucuronide (more potent analgesic than morphine)

28
Q

Where is the intracellular site of phase I drug metabolism?

A

Phase I drug metabolizing enzymes are localized to the smooth endoplasmic reticulum

29
Q

Where is the intracellular site of phase II drug metabolism?

A

Phase II drug metabolizing enzymes are localized predominantly in the cytosol of the cell; except with glucuronidation, which is localized to the smooth ER

30
Q

Largest family of drug metabolizing enzymes.

A

CYPs (Cytochrome P-450)

31
Q

The majority of drug metabolism in the body is performed by _______ CYP enzymes.
CYPs are the predominant phase ___ drug metabolizing enzyme system.

A

hepatic

phase I

32
Q

How do CYP enzymes work, i.e. metabolize?

A

Oxidize drugs by adding oxygen, producing water as a by-product

33
Q

How does malnutrition affect CYP activity?

A

Can decrease it as these enzymes require dietary protein, iron, folic acid and zinc for full activity

34
Q

Describe the nomenclature of CYP enzymes.

CYP3A4 for example.

A

3 - family
A - sub-family
4 - isozyme

35
Q

_________ metabolizes the largest fraction of currently marketed drugs.

36
Q

What are the different phase II drug metabolizing enzymes?

A 
UDP-glucuronosyltransferases (UGTs)
Sulfotransferases (SULTs)
Glutathione S Transferases (GSTs)
N-acetyltransferases (NATs)
Thiopurine Methyltransferases (TPMT)
37
Q

Which phase II drug metabolizing enzyme type metabolizes drugs the most?

A

The fraction of drugs metabolized is equally split between UGTs, SULTs, GSTs, and NATs

38
Q

Where are UGTs localized?
What do they catalyze transfer or?
Describe the effect of the enzyme on the parent drug.
How many UGT enzymes are there in humans?

A

Smooth ER
glucuronic acid
Glucuronidated drugs are more polar and more easily excreted
19

39
Q

Where are SULTs localized?
What do they add?
Describe the metabolite.
How many SULT enzymes are there in humans?

A

Cytosol
Add sulfate to hydroxyl groups of drugs
Sulfated drugs are more polar and more easily excreted
11

40
Q

Where are GSTs localized?
What do they add?
What is the result of transfer?
How many GSTs are there in humans?

A

Cytosol (main) or microsomal
Add GSH (glutathione)
Intracellular anti-oxidant –> causes a reactive drug to be less toxic
20+

41
Q

Where are NATs localized?
What do they add?
What are they subject to?
How many are there in humans?

A

Cytosolic
Acetyl group from Acetyl-CoA
Subject to genetic polymorphisms - variability in drug response
2 - NAT1 and NAT2

42
Q

Where are TPMTs localized?
What do they add?
What are they subject to?

A

Cytosolic
Add methyl from S-adenosylmethionine
Subject to genetic polymorphisms, can have dramatic effects on drug safety

43
Q

What are the major factors that affect drug metabolism?

A

Age
drug interactions
disease state
Genetic polymorphisms

44
Q

Describe how age affects metabolism.

A

Infants have almost no hepatic CYP activity - takes babies approx. 1 year after birth until they have a reasonable level of drug metabolizing enzymes
By age 2 - same level as adults

45
Q

Process where a cell synthesizes an enzyme in response to a drug or other chemical.

A

Enzyme induction

46
Q

Consequence of CYP induction.

A

Increased drug metabolism

47
Q

What are consequences of increased drug metabolism?

A

Decreased plasma concentration
Decreased drug activity
Increased drug activity

48
Q

_______ induces some drug metabolizing enzymes

49
Q

What is the consequence of CYP inhibition?

A

Decreased drug metabolism

50
Q

Decreased drug metabolism has the following consequences.

A

Higher plasma concentration
Increased therapeutic effect
Increased drug toxicity

51
Q

What are diseases that decrease CYP activity?

A

Liver disease
kidney disease
inflammatory diseases
infection

52
Q

SNPs affect what?

A

the protein

53
Q

What are the common phase I SNPs?

A

CYP2C9

CYP2D6

54
Q

What are the common phase II SNPs?

A

UGT1A1

NAT2

55
Q 
CYP2C9
metabolizes what?
Polymorphism results in what?
Describe the effect on dosage.
What may occur if the dosage is not altered?
A

Metabolizes warfarin
Polymorphism results in decreased activity/metabolism
Dosage must be lowered in these patients, else extensive bleeding may occur

56
Q

CYP2D6
Metabolizes what?
What phenotypes are possible?

A

Codeine to morphine

URM, EM, IM, PM

57
Q

Describe EM.

A

Extensive metabolizers - considered to have normal enzymatic activity

58
Q

Describe IM. PM.

A

IM - lower metabolic activity

PM - almost no metabolic activity (i.e. no pain relief)

59
Q

Describe URMs.

A

Ultra-rapid metabolizers - significantly increased CYP2D6 activity - possess multiple copies of CYP2D6 gene

60
Q

UGT1A1
Metabolizes what?
Polymorphisms cause what?
What are patients with the polymorphism at increased risk of?

A

Metabolizes SN-38 - anti-cancer compound (inactivates)
Polymorphisms decrease its activity
Patients with UGT1A1 are at increased risk for diarrhea and dose-limiting bone marrow suppression

61
Q

NAT2
Metabolizes what?
Number of polymorphisms here?
Possible phenotypes?

A

Metabolizes isoniazid (TB), caffeine, cancer causing chemicals
23+
Rapid or slow acetylators

62
Q

Describe slow acetyaltors and the effect with isoniazid.

A

More susceptible to isoniazid toxicity (neuropathy, hepatotoxicity) - higher risk of developing certain types of cancers

Nursing Pharmacology (30 decks)

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