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Principles of disease > Drug Metabolism > Flashcards

Drug Metabolism Flashcards

1
Q

Describe phase 1 metabolism

A

Creating/modifying functional group
Creation - oxidation
Modifying - hydrolysis

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2
Q

Describe phase 2 metabolism

A

Products:

Less active
More hydrophilic
Larger
Weak acids
More likely to bind albumin

Availability of co-factor determines reaction capacity

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3
Q

Define Drug Metabolism:

A

Biochemical modification to pharmaceutical substance by living organisms
Usually through activity of specialised enzymes

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4
Q

4 main sites of drug metabolism?

A

Liver
Lungs
Gut Lining
Kidneys

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5
Q

What is a prodrug?

A

Precursor to a drug
Activated by metabolism e.g. Codeine

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6
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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7
Q

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

A

Many drugs can be metabolised by more than one enzyme
Substrate is specific to many different enzymes

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8
Q

What are the 3 types of phase 1 metabolism reaction?

A

Hydrolysis
Oxidation
Reduction
[HOR]

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9
Q

Whats the function of phase 1 metabolism?

A

Increase polarity of compound
Provide active site for phase 2 to occur

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10
Q

What family of enzymes carries out phase 1 metabolism?

A

P-450 family of enzymes

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11
Q

What is the Prefix for the enzymes in phase 1 metabolism?

A

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

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12
Q

3 enzymes in phase 1 metabolism?

A

CYP3A4
CYP2D6
CYP1A2

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13
Q

Where is CYP3A4 found?

A

In Liver

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14
Q

What does CYP2D6 metabolise?

A

Antidepressants
Antipsychotics
Converts codeine to morphine

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15
Q

How does smoking affect CYP2D6?

A

CYP2D6 is induced by Smoking

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16
Q

What does CYP1A2 metabolize?

A

Theophylline

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17
Q

Which phase 1 enzyme isnt induced by smoking?

A

CYP3A4 isn’t induced by smoking

18
Q

What phase involves conjugation?

A

Phase 2 metabolism involved conjugation

19
Q

What is conjugation?

A

Combining drugs with other substances to terminate their activity

20
Q

How does conjugation make excretion of the drug easier?

A

Conjugated drugs have an increased water solubility

21
Q

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

A

Glucuronic Acid
Glutathione
Sulphate
Acetate

22
Q

Does conjugation deactivate all drug metabolites?

A

Most, but not all are inactivated

23
Q

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

A

Other drugs/herbals can cause enzyme induction & inhibition, affecting metabolic rates

24
Q

What is enzyme induction?

A

Substance causes increased synthesis of enzyme leading to greater metabolic rate

25
Q

What are some commmon inducers?

A

Other drugs, herbals, smoking & alcohol.

26
Q

How long does induction take to become apparent?

A

Weeks -> months

27
Q

Is enzyme inhibition reversible?

A

Some enzyme inhibition is reversible but not all

28
Q

What are some common substances that inhibit drug metabolising enzymes?

A

Erythromycin & Clarithromycin
(Grapefruit)

29
Q

What is pharmacogenetics?

A

Wide genetic variability in pharmacokinetics
Role of genome in drug response

30
Q

What are the consequences of ‘bad’ pharmacogenetics?

A

Therapeutic failure
Adverse reactions

31
Q

How can genetic variation lead to drug toxicity?

A

Genetic variation can cause:

Absence/deficiency in enzymes
Overly high drug level
Drug toxicity

32
Q

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

A

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

33
Q

What two aspects of the liver can effect drug metabolism?

A

Liver Disease
Hepatic Blood Flow

34
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

35
Q

How is a pubescant childs metabolism differnt to an adults?

A

By puberty a childs metabolism is faster than an adults

36
Q

Which parameters affecting drug metabolism are affected in the elderly?

A

Lower liver weight, renal function, plasma protein & lean body mass

37
Q

How does chronic disease in the elderly affect drug metabolism?

A

Chronically ill elderly people are on multiple meds which can interact or overpower the body.

38
Q

How does gender affect drug metabolism?

A

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

39
Q

How does pregnancy effect drug metabolism?

A

Hormonal changes in 2nd/3rd trimester induce some drug metabolising enzymes

40
Q

How does ethnicity effect drug metabolism?

A

Variation in expression of P-450 genes leads to different levels of drug metabolising enzymes between races

41
Q

What is knowing ADME important for?

A
  • Choosing method of administration
  • Choosing safe & effect Doses/Frequency
  • Making changes based on drugs, illness or physiological factors

Principles of disease (47 decks)

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