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Medicine Term One > Drug metabolism > Flashcards

Drug metabolism Flashcards

1
Q

define Drug metabolism

A

biochemical modification of pharmaceutical substances by living organisms usually through specialized enzymatic activity

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2
Q

Where are drugs usually metabolised

A

The liver

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3
Q

What happens to lipid soluble drugs instead of excretion

A

passively reabsorbed from renal filtrate and absorbed back into the blood

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4
Q

What is the purpose of drug metabolism and

what else can occur from the process that can cause an adverse reaction

A

increase water solubility to aid excretion
deactivate compounds
Toxic metabolites

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5
Q

What are pro drugs (example)

A

drugs activated following metabolism e.g. codeine

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6
Q

What is the most important metabolising enzyme family in the liver

A

Cytochrome P450

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7
Q

What are the two ways metabolising enzymes can be expressed

A

constitutively -continuously

or Induced in the presence of substrate

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8
Q

What process occur in phase 1 metabolism and what is the purpose of the processes

A

Oxidation Reduction Hydrolysis

To increase polarity

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9
Q

How is drug specificity determined in the liver

A

isoform of cytochrome P450

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10
Q

What are the three isoforms of cytochrome P450

A

CYP1A2
CYP2D6
CYP3A4

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11
Q

What are the drug substrates for
CYP1A2
CYP2D6
CYP3A4

A

CYP1A2 - theophyline - respiratory diseases
CYP2D6 - codeine - pain relief
CYP3A4 - cyclosporine - immunosuppressant drug

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12
Q

What is the purpose of CYP2D6 and what induces the enzyme

A

metabolises antidepressant

smoking

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13
Q

What would happen if someone who smokes and takes antidepressants stops smoking

A

Induced levels go away but level of drug concentration remains this causes an accumulation of the drug resulting in toxicity

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14
Q

What would happen to people that don’t have CYP2D6 enzyme and take codeine

A

Cant metabolise to morphine so don’t receive any pain relief

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15
Q

What enzyme is a major constitutive enzyme

A

CYP3A4

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16
Q

How is it easy to cause toxicity giving smoking patients theophlyine

A

As smoking induces enzyme CYP1A2, therefore if patient was to stop smoking the concentration of the drug would be to high as enzymes level decrease, the accumulation causes toxicity

17
Q

What are the factors affecting metabolism

A 
Other drugs/herbals/natural substances
Genetics
Hepatic blood flow
Liver disease
Age
Sex
Ethnicity
Pregnancy
18
Q

What are the most common enzyme inducers

A

alcohol and smoking

19
Q

What is enzyme induction and

how long does it take to take an effect

A

Increase synthesis of enzymes therefore increases the metabolism of a drug
Is a slow process = progressive loss of drugs affect

20
Q

How long does it take for enzyme inhibition to occur

A

Immediate response

21
Q

What ar common enzyme inhibitor drugs

A 
cimetidine - inhibits stomach acid production
erythromycin - antibiotic 
clarithromycin - antibiotic 
ketoconazole - fungal infections 
grapefruit
22
Q

what is pharmacogenetics and what is the problem

A

A branch of pharmacology concerned with effects of genetic factors
You will over treat or under treat some patients

23
Q

wha is the consequences genetic variation in pharmacology

A

therapeutic failure or an adverse drug reaction

24
Q

How is genetic variation tackled

A

Wide variability in the response to drugs between individuals
Drug metabolising enzymes are often expressed in multiple forms

25
Q

Gene mutations resulting in lack or decreased activity of an enzyme results in what

A

Increased drug toxicity

26
Q

Gene varriation or mutation resulting in multiple expressions of a particular metabolising enzyme results in what

A

enhanced metabolism and reduced drug effect or drug resistance

27
Q

What are the Four phenotype subpopulations of metabolizers

A 
Poor metabolizers (PM)
Intermediate metabolizers (IM)
Extensive metabolizers (EM)
Ultrarapid metabolizers (UM)
28
Q

When is the rate of metabolism the best in humans

A

at puberty

29
Q

What are the levels of drug metabolising enzymes in children

A

deficient or reduced

30
Q

What happens to metabolising in pregnancy

A

is induced

31
Q

What are the factors that effect drug metabolism in elderly patients

A 
plasma protein, 
lean body mass 
decreased liver weight 
More likely to have chronic disease so on multiple drug therapy 
renal functions aren't as efficient
32
Q

How might ethnicity effect drug metabolism

A

due to racial differences in the genetic expression of cytochrome P-450 isoforms.

Medicine Term One (59 decks)

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