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Pharmacokinetics > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What is the definition of metabolism?

A
  • conversion of drug to a more polar, water soluble, ionized substance usually with reduced pharmacological activity and toxicity
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2
Q

What are the sites of metabolism?

A
  • bloodstream
  • kidneys
  • brain
  • muscle tissue
  • wall of GI tract (e.g. bacteria)
  • lungs
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3
Q

The liver is the main organ of ________

A

biotransformation

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4
Q

What are the three chemical processes of phase 1 hepatic metabolism?

A

oxidation. reduction and hydrolysis

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5
Q

What are the three chemical process of phase 2 metabolism?

A

glucuronidation, acetylation and sulfation

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6
Q

What metabolic processes do barbiturates undergo in the body?

A
  • glucuronidation

- oxidation

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7
Q

What metabolic processes do benzodiazepines undergo in the body?

A
  • N-dealkylation
  • hydroxylation
  • glucuronidation
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8
Q

What are the metabolic processes that morphine undergoes in the body?

A
  • glucuronidation
  • morphine 6-glucuronide
  • morphine 3-glucuronide
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9
Q

10% of codeine is demethylated to _____

A

morphine

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10
Q

The majority of anti-psychotic agents undergo the process of _____, but some also undergo glucuronidation

A

oxidation

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11
Q

What is the metabolic process that ethanol typically undergoes?

A

oxidation

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12
Q

What is the most prevalent phase 1 metabolism process?

A

oxidation

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13
Q

What are the chemical requirements to carry out an oxidation reaction?

A

requirement of NADPH, molecular oxygen and heme protein

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14
Q

Where in the cell are many of the phase 1 oxidation processes carried out?

A

in the smooth endoplasmic reticulum

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15
Q

Key element in the oxidative process is the hemeprotein cyctochrome _______

A

cytochrome P450 enzyme system

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16
Q

What families of the CYP enzyme is drug metabolism carried out by?

A
  • carried out my families 1, 2 and 3
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17
Q

How many major P450 isoenzymes is the metabolism of drugs dominated by?

A

6

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18
Q

What are the drug substrates for enzyme CYP1A2?

A

phenacetin and theophylline

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19
Q

What are the drug substrates for enzyme CYP2C8/9/10?

A

hexobarbital, phenytoin

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20
Q

What are the drug substrates for the enzyme CYP2C18/19?

A

diazepam, mephenytoin

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21
Q

What are the drug substrates for the enzyme 2D6?

A

imipramine, propranol

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22
Q

What are the drug substrates for the enzyme CYP2E1?

A

acetaminophen

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23
Q

What are the drug substrates for the enzyme CYP3A4?

A

erythromycin and cyclosporin

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24
Q

Smoking _____ the enzyme CYP1A2, resulting in the activation of benzopyrene, a carcinogen in the cigarette smoke

A

induces

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25
Q

In what enzyme is there quite a bit of genetic polymorphism?

A

CYP2C9, CYP2C19

5% of caucasians and 20% of asians are poor metabolizers

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26
Q

There is an inhibition of S-Warfarin metabolism by _____

A

amiodarone

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27
Q

What other enzyme exhibits polymorphism between groups of individuals?

A

CYP2D6 (ultra rapid metabolizers of CYP2D6 need ultra high doses)

28
Q

70% of the CYP3A4 isoform are present in the ___. What is the consequence of this?

A

gut

- this decreases bioavailability of the drug

29
Q

The high incidence of drugs metabolized by CYP3A4 means that most of metabolism of drugs occurs in the ___

A

gut

30
Q

Chronic alcoholism induces _____ and glutathione depletion leading to an accumulation of NAPQ1, a lethal byproduct of acetaminophen - leads to sever liver injury and possibly liver failure

A

CYP2E1

31
Q

Alcoholism causes ____ of the liver, causing it to quit

A

oxidation

32
Q

What are the two major reduction reactions?

A

nitro-reduction

azo-reduction

33
Q

Where are reduction reactions most likely carried out?

A
  • mostly carried out in the intestinal microflora - they carry out these reactions much more efficiently than in the livers of mammals
34
Q

Reduction reactions are common for ____ administered drugs

A

orally

sulfasalazine, chloramphenicol

35
Q

What are hydrolysis reactions mostly carried out by?

A

usually performed through respective esterase in the liver. They are also carried out by esterases in plasma and other tissues

36
Q

Esterases hydrolyse esters to ____ and ________

A

alcohols

carboxylic acids

37
Q

Phase 2 reactions involve what?

A

chemical conjugation or synthesis

38
Q

What do phase 2 reactions generally result in?

A
  • generally increase the water solubility and result in pharmacological deactivation
39
Q

What must a compound be in order for phase 2 reactions to occur?

A
  • a compound must be chemically active (usually occurs after phase 1 reactions)
40
Q

What occurs in conjugation reactions?

A

a compound of a metabolite is combined with an endogenous molecule

41
Q

What are the different factors that are known to affect drug metabolism?

A
  • species (different animals have different enzyme titres)
  • genetics
  • age
  • disease state
  • drug/drug interactions
  • food
42
Q

Describe the paradox of modern drug development?

A
  1. clinical trials provide evidence of efficacy and safety at usual doses in populations (usually seen to be efficacious and safe in the LARGE group of HEALTHY people)
  2. physicians treat individual patients who can vary widely in their response to drug therapy (can have no response, can be efficacious, or can have an adverse drug reaction)
43
Q

What was the first recognized genetic polymorphism?

A

N-acetyltransferase (NAT-2)

44
Q

Is isoniazid active or not?

A

NO

45
Q

The rate and extent of metabolism will affect the efficacy of the drug in treating ______

A

tuberculosis (fast and slow acetylators)

46
Q

What groupings of people are rapid acetylators

A

inuit, japanese, american indian

47
Q

Total body water and extracellular fluid in newborns is _____ than in adults

A

more than

48
Q

What happens to the body composition of elderly individuals?

A
  • the lean body mass of the person decreases, while the body fat increases
49
Q

Newborns have ____ titres of hepatic microsomal enzymes. What does this do to glucuronidation reactions?

A

low

It decreases the extent of glucuronidation reactions

50
Q

What is the definition of pharmacogenomics?

A
  • avoiding adverse drug reactions from genetics and trying to maximize efficacy
51
Q

What should be done with someone that is at a high risk of ADR’s?

A
  • should treat them with an alternative medication
52
Q

What should be done with someone who is at a medium risk of ADR’s?

A
  • you should treat them with an alternative drug or dose
53
Q

What should be done with someone who is at a low risk of ADR’s?

A
  • you keep the drug
54
Q

When you decrease the protein in the diet, what do you do to the drug metabolizing capacity?

A

you decrease the drug metabolizing capacity

55
Q

When you decrease the lipids and you decrease the EFA, what do you do to the metabolism of ethylmorphine and hexobarbitone?

A
  • you decrease it
56
Q

High glucose intake does what to barbiturate metabolism?

A
  • it inhibits barbiturate metabolism
57
Q

Why does food increase the bioavailability of medications?

A

Because they increase the splanchnic blood flow

58
Q

Charcoal broiled meats and smoked fish are potent inducers of what enzyme?

A

cytochrome p450 enzyme system

59
Q

Grapefruit juice inhibits intestinal ____ enzymes and increase bioavailability of cyclosporine

A

p450

60
Q

What enzyme family does grapefruit juice inhibit?

A

CYP3A

61
Q

What drugs are metabolized by the family of CYP3A?

A

antihistamines, benzodiazepines, immunosuppressants

62
Q

What did the ingestion of grapefruit juice result in in those patients taking large doses of nifedipine and terazosin? (used for blood pressure control)

A

marked hypotension

63
Q

What enzyme does St. John’s Wart have an effect on and what is the result of this?

A

it induced CYP3A

- produces subtherapeutic doses of HIV drugs

64
Q

What drug interactions are associated with ginseng?

A
  • potential interactions with anti-depressants (headache and mania)
  • warfarin (increased bleeding time), steroids (stronger effects)
65
Q

What is the drug interactions associated with ginkgo and garlic?

A
  • it increases the bleeding time with warfarin (increased risk of hemorrhages)
  • —- simple advice! do not mix herbs and drugs!
66
Q

What is the michaelis-menton equation?

A

Vmax C/(Km + C)

C= [drug]
Vmax = maximum rate 
Km = michaelis constant =0.5 Vmax

Pharmacokinetics (4 decks)

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