Drug Metabolism Flashcards

1
Q

Define drug metabolism?

A

Biochemical modification of pharmaceutical substances by living organisms usually through specialised enzyme activity.

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2
Q

Why is drug metabolism essential?

A

Limits the life of a substance in the body.

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3
Q

Are drugs usually metabolised before or after excretion?

A

Before

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4
Q

Where are the important sites of drug metabolism?

A

Liver
Lining of gut
Kidneys
Lungs

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5
Q

What are the 2 purposes of metabolism?

A

Increase water solubility

Deactivate compounds

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6
Q

What are the 3 effects of metabolism?

A

Loss of pharmacological activity
Decrease of activity
Increase of activity

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7
Q

What are the 3 productions of toxic metabolites?

A

Direct toxicity
Carcinogenesis
Teratogenesis

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8
Q

Enzymes in drug metabolism are very specific/have a wide specificity.

A

Wide

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9
Q

How are some enzymes expressed?

A

Constitutively.

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10
Q

How are other enzymes expressed or induced?

A

In the presence of a particular substrate.

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11
Q

How many phases are there?

A

2

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12
Q

What are the phase 1 reactions?

A

Oxidation
Reduction
Hydrolysis

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13
Q

What is increased in phase 1?

A

Polarity of compound, providing an active site for phase 2.

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14
Q

What are the most important super family of metabolising enzymes?

A

P-450

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15
Q

Is specificity usually relative or absolute?

A

Relative

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16
Q

What is a major constitutive enzyme in human liver?

A

CYP3A4

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17
Q

What drug is responsible for the metabolism of antidepressants?

A

CYP2D6

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18
Q

Why are 5-10% of the population immune to analgesic actions of codeine?

A

Reduced or absent expression of CYP2D6

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19
Q

What is CYP1A2 induced by?

A

Smoking

20
Q

What is CYP1A2 important in?

A

Metabolism of theophylline.

21
Q

What does phase 2 include?

A

Conjugation

22
Q

What does conjugation increase?

A

Water solubility, enhancing excretion of the metabolised compound.

23
Q

What factors affect metabolism?

A
Other drugs/herbals/natural substances
Genetics
Hepatic blood flow
Liver disease
Age
Sex
Ethnicity
Pregnancy
24
Q

What happens when a drug is induced?

A

Increases metabolism of drugs metabolised by that enzyme.

25
Q

Induction is a ______ process.

A

Slow

26
Q

What are the 2 most common enzyme inducers?

A

Alcohol

Smoking

27
Q

What may inhibit drug metabolising enzymes?

A

Commonly used drugs, herbal medicines and food stuffs.

28
Q

What are common drug metabolising inhibitors?

A

Cimetidine
Ketoconazole
Grapefruit

29
Q

What can be the consequences of genetic variation?

A

Therapeutic failure

Adverse drug reactions

30
Q

How are pharmacogenetics often expressed?

A

In multiple forms

31
Q

What are common differences in gene expression?

A

Interindividual

32
Q

What does a lack/decreased activity of an enzyme result in?

A

Increased drug toxicity

33
Q

Approx __ nucleotide polymorphisms are known?

A

70

34
Q

What are the 4 phenotype subpopulations of metabolisers?

A

Poor
Intermediate
Extensive
Ultrarapid

35
Q

How many drugs does CYP2C9 commonly metabolise?

A

16

36
Q

What are 2 substrates of CYP2C9?

A

Warfarin

Phenytoin

37
Q

What are drug metabolising enzymes are often ______ or ______ in the fetus or premature infant.

A

Deficient

Reduced

38
Q

What builds up due to renal function being deficient in children?

A

Metabolites to toxic level

39
Q

By what age can children metabolise drugs more than adults?

A

2

40
Q

Who are more prone to drug toxicity?

A

Women

41
Q

What does pregnancy induce?

A

Certain drug metabolising enzymes.

42
Q

What factors can decrease and alter drug metabolism in the elderly?

A

Plasma protein
Lean body mass
Liver weight

43
Q

Why are the elderly more likely to be on multiple drug therapy?

A

Chronic disease

44
Q

Where are the difference in racial genetic expression?

A

Cytochrome P-450

45
Q

What do steroids do to your blood sugars?

A

Increases it