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Biochemical Pharmacology > Pharmacogenomics > Flashcards

Pharmacogenomics Flashcards

1
Q

What is pharmacogenomics?

A
  • The influence of genetic variation on drug response
  • Correlating gene expression or polymorphism with a drug’s efficacy or toxicity.
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2
Q

What are the goals of pharmacogenomics?

A
  • Maximizing efficacy
  • Minimizing toxicity
  • Predicting patient response for personalized medicine
  • Aiding in drug development.
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3
Q

What is the difference between pharmacogenetics and pharmacogenomics?

A

Pharmacogenetics
* individual gene-drug interactions,
* Involving one or two genes with a dominant effect on drug response.

Pharmacogenomics
* study of genomic influence on drug response
* often using high-throughput data to study complex interactions.

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4
Q

What is the potential of pharmacogenomics?

A

To guide the choice of drug and dose on an individual basis based on genetic information
leading to personalized medicine.

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5
Q

What is a mutation?

A
  • A difference in the DNA code that occurs in less than 1% of the population
  • Associated with rare diseases.
  • Cystic fibrosis, sickle cell anemia, Huntingtons disease
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6
Q

What is a polymorphism?

A
  • A difference in the DNA code that occurs in more than 1% of the population.
  • Less likely to be the main cause of disease
  • No visible clinical impact
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7
Q

What is a single nucleotide polymorphism (SNP)?

A

DNA sequence variation that occurs when a single nucleotide in the genome sequence is altered.
* Occur in at least 1% of the population
* Make up about 90% of all human genetic variation.
* They can be inherited or can arise as cells divide.

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8
Q

How can SNPs affect drug response?

A

Causes changes in
* drug metabolism (pharmacokinetics)
* drug targets (pharmacodynamics)
such as enzymes, receptors, or transporters

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9
Q

What are cytochrome P450 enzymes, and why are they important in pharmacogenomics?

A
  • Group of enzymes that are commonly found with SNPs
  • Primary driver in breaking down around 50% of prescription drugs in our body.
  • Variations in expression and regulation of CYPs can lead to differences in drug response, making them targets for pharmacogenomics research.
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10
Q

What is the role of CYP enzymes in drug metabolism?

A

Responsible for metabolizing most clinically important drugs.

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11
Q

What is CYP2D6?

A

CYP2D6 is an enzyme that metabolizes about 25% of all drugs in the body

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12
Q

What is the role of CYP2D6 in the conversion of codeine to morphine?

A

CYP2D6 is responsible for the O-demethylation reaction that drives the conversion of codeine to morphine.

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13
Q

How does a polymorphism in the CYP2D6 gene affect codeine metabolism?

A

Can cause low metabolism of drugs which results in a lack of conversion of codeine into morphine.

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14
Q

What happens if there is an inactive polymorphism in CYP2D6?

A

The conversion of codeine to morphine will not occur, resulting in the prodrug being ineffective.

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15
Q

What is the prevalence of inactive polymorphisms?

A

5-10% in European Caucasians
Less than 2% in Southern Asians.

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16
Q

What is the role of CYP2D6 in the metabolism of tamoxifen?

A

Responsible for the metabolism of tamoxifen into its active metabolites
which are more effective at preventing the recurrence of breast cancer.

17
Q

What is acetylation and what is an example of a drug that undergoes this process?

A
  • A phase II reaction in which an acetyl group is added to a drug or metabolite.
  • Isoniazid - treats tuberculosis
18
Q

What is the role of N-acetyltransferase in the acetylation of isoniazid?

A

The enzyme responsible for acetylating isoniazid.

19
Q

What is the difference between fast and slow acetylators in drug metabolism?

A

Differ in their ability to metabolize drugs through the enzyme N-acetlytransferase.

20
Q

What is the difference in blood levels of isoniazid between fast and slow acetylators?

A

Blood levels are 4-6 times higher in slow acetylators than in fast acetylators.

21
Q

What happens when isoniazid undergoes fast or slow acetylation?

A

Results in diversion to two separate toxic pathways.

22
Q

How does acetylation of isoniazid differ between different ethnic populations?

A

Slow acetylators
45% of Caucasian and African-American populations in the US
Some Europeans

Fast acetylators
>90% of Asian and Inuit populations in US

23
Q

What is the Roche AmpliChip P450 Test used for?

A

An aid to clinicians in determining therapeutic strategy and treatment dose for therapeutics.

24
Q

How does Roche AmpliChip P450 Test work?

A

by identifying a patient’s CYP2D6 and CYP2C19 genotype from genomic DNA extract.

25
Q

What is personalised medicine?

A

An approach to clinical practice where a particular treatment is not chosen based on the ‘average patient’ but on characteristics of an individual patient.

26
Q

What is the impact of pharmacogenomics on drug discovery process?

A

Has the potential to provide:
* improved sensitivity and tolerance,
* increased statistical power and reduced costs,
* additional opportunities for revenue generation
* higher market prices for more efficacious drugs.

27
Q

What is the metabolizer phenotype?

A

Refers to the genetic variation in metabolic enzymes that affect the way individuals process drugs.
* Poor metabolizers
* ultra-rapid metabolizers
* extensive metabolizers.

28
Q

What happens in poor metabolizers?

A

Increased efficacy
The active drug metabolite may accumulate
usually require a lower dose to avoid toxic accumulation.

29
Q

What happens in Ultra-rapid metabolizers?

A

Decreased efficacy
The active metabolite is rapidly inactivated,
usually requiring a higher dose to offset inactivation.

30
Q

What happens in prodrugs?

A

Decreased efficacy
- may occur because the prodrug may accumulate,
- requiring a lower dose to avoid toxic accumulation

Increased efficacy
- may occur with rapid onset of effect,
- may require a lower dose to prevent excessive accumulation of the active metabolite.

31
Q

What are metabolic polymorphisms?

A

Variations in genes that affect drug metabolism in individuals.

32
Q

What does the FDA require genetic tests for?

A

Certain therapies.

33
Q

Advantages of pharmacogenomics

A
  1. Predict a patients response to drugs
  2. Develope customized prescriptions
  3. Minimize adverse effects
  4. Improve efficacy and patient compliance
  5. Improve rational drug development
34
Q

Limitations of pharmacogenomics

A
  1. Many genes involved in drug action so identifying drug target is difficult
  2. Insufficient validation of study resullts
  3. Expensive
  4. Ethical issues

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