Drug Metabolism Flashcards

1
Q

Define Drug Metabolism:

A

A biochemical modification to pharmaceutical substance by livin organisms, ususally through activity of specialzed enzymes.

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2
Q

4 main sites of drug metabolism?

A

Liver
Lungs
Gut Lining
Kidneys

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3
Q

What is a prodrug?

A

A precursor to a drug which is converted to its active form by metabolism. e.g. Codeine

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4
Q

What are the 3 outcomes of metabolism on a drug?

A

Production of toxic metabolites
Activation (prodrugs)
Deactivation/loss of activity

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5
Q

What does the “wide substrate specificty” of metabolic enzymes mean?

A

It means many drugs can be metabolized by more than one enzyme

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6
Q

What are the 3 types of phase 1 metabolism reaction? [HOR}

A

Hydrolysis
or Oxidation
or Reduction

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7
Q

Whats the function of phase 1 metabolism?

A

To increase polarity of the compound and provide an active site for phase 2 to occur

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8
Q

What family of enzymes carries out phase 1 metabolism?

A

P-450 family of enzymes

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9
Q

Prefix for the enzymes in phase 1 metabolism?

A

CYP- is the prefix followed by no-letter-no.

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10
Q

3 enzymes in phase 1 metabolism?

A

CYP3A4
CYP2D6
CYP1A2

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11
Q

Where is CYP3A4 found?

A

In the Liver

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12
Q

What does CYP2D6 metabolize?

A

CYP2D6 metabolizes antidepressants, antipsychotics & ocnverts codeine to morphine

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13
Q

How does smoking affect CYP2D6?

A

CYP2D6 is induced by Smoking.

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14
Q

What does CYP1A2 metabolize?

A

Theophylline

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15
Q

Which phase 1 enzyme isnt induced by smoking?

A

CYP3A4 isnt induced by smoking

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16
Q

What phase involves conjugation?

A

Phase 2 metabolism involved conjugation

17
Q

What is conjugation?

A

Conjugation is combining drugs with other substances to terminate their activity

18
Q

How does conjugation make excretion of the drug easier?

A

Conjugated drugs have an increased water solubility

19
Q

What substances are used to conjugate the metabolites formed in phase 1?

A

Glucuronic Acid
Glutathione
Sulphate
Acetate

20
Q

Does conjugation deactivate all dru metabolites?

A

Most but not all are inactivated

21
Q

In what two ways do other drugs/herbal meds affect drug metabolism?

A

Other drugs & herbals can cause enzyme induction & inhibition. Therfore affecting metabolic rates

22
Q

What is enzyme induction?

A

One substance causes an increased synthesis of the enzyme leading to a greater metabolic rate.

23
Q

What are some commmon inducers?

A

Other drugs, herbals, smoking & alcohol.

24
Q

How long does induction take to become apparent?

A

Weeks -> months

25
Q

Is enzyme inhibition reversible?

A

Some enzyme inhibition is reversible but not all

26
Q

What are some common substances htat imhibit durg metabolizing enzymes?

A

Erythromycin & Clarythromycin
Grapefruit

27
Q

What is pharmacogenetics?

A

The wide genetic variability in pharmcokinetic & pharmacodynamic reponse to drugs between individuals

28
Q

What are the consequences of ‘bad’ pharmacogenetics?

A

Therapeutic failure
Adverse reactions

29
Q

How can genetic variation lead to drug toxicity?

A

Genetic variation
-> abscence/deficiency in an enzyme
-> Overly high drug level
-> Drug toxicity

30
Q

How can genetic variation lead to tehrapeutic failure without adverse effectS?

A

Over production of an ezyme
Overly high metabolic activity
Low drug conc. in blood
Failure of therapy

31
Q

What two aspects of the liver can effect drug metabolism?

A

Liver Disease
Hepatic Blood Flow

32
Q

What are the 2 main differnces in the drug metabolism of infants to adults?

A

Infants have:
- reduced or absent drug metabolizing enzymes
- Reduced renal function

33
Q

How is a pubescant childs metabolism differnt to an adults?

A

By puberty a childs metabolism is faster than an adults

34
Q

Which parameters affecting drug metabolism are affected in the elderly?

A

The elderly have a lower liver weight, renal function, plasma protein & lean body mass

35
Q

How does chronic disease in the elderly affect drug metabolism?

A

Chronically ill elderly people ar eon multiple meds which can interact or simply overpower the body.

36
Q

How does gender affect drug metabolism?

A

It effects all 4 areas of pharmacokinetics:
- Absorption
- Distribution
- Metabolism
- Excretion

37
Q

How does pregnancy effect drug metablism?

A

Hormonla changes in 2nd/3rd trimester induce some durg metabolizing enzymes

38
Q

How does ethnicity effect drug metabolism?

A

Variation in expression of P-450 genes leading to different levels of drug metabolizing enzymes between races

39
Q

What is knwing ADME importnat for?

A
  • Choosing methd of administrstion
  • Choosing safe & effect Dosaes/Frequency
  • Making changes based on drugs, illness or physioloical factors