Introduction of Drug Metabolism Flashcards

1
Q

What does ADME stand for?

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

Stages of drug metabolism

A
Stage 1 (modification) e.g. oxidation - Hydrophobic drug
Stage 2 (Conjugation) e.g. methylation - Make drug hydrophillic 
Stage 3 (Excretion) e.g. Efflux from the cell
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3
Q

What is polymorphism?

A

Genetic changes

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4
Q

What are xenobiotics?

A

substances which are found in the body which are not naturally produced in the body

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5
Q

How is drug metabolism regulated?

A

By nuclear receptor which live in the cytoplasm of the cell

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6
Q

What is functionalisation?

A

When by phase I reaction, the functional group is exposed (e.g. -OH) so it can undergo conjugation

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7
Q

What happens during phase II drug metabolism?

A

Detoxification of drug

Gives rise to water soluble and easy to excrete products

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8
Q

Name an anti-epileptic drug

A

Phenytoin

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9
Q

Explain the functionalisation of phenytoin

A

Phenytoin (highly lipophillic) -CYP-> 4-hydroxy-phenytoin (slightly soluble in water) -UGT + UDP-GA-> 4-hydroxy-phenytoin-glucuronide (very soluble in water)

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10
Q

What is the most common form of phase I drug metabolism

A

oxidation by Cytochrome p450

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11
Q

Describe flavin-containing monooygenase (FMO)

A

A type of oxidation enzyme
Membrane bound flavin mononucleotide/ flavin adenine nucleotide containing protein
High concentrations in the liver
Subcellular location: smooth endoplasmic reticulum
Cofactors - NADPH and molecular oxygen (O2)

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12
Q

What is FMO3?

A

A gene which provides instructures to make FMO

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13
Q

Disease related to polymorphism in FMO3

A

Fish odour syndrome

  • secrete lots of TMA in urine, sweat, breath
  • severe psychological consequences
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14
Q

Describe cytochrome p450

A

Terminal oxidase in an electron transfer system of the endoplasmic reticulum

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15
Q

Functions of cytochrome p450

A
  • steroid biosynthesis
  • bile acid biosynthesis
  • xenobiotic metabolism
  • fatty acid metabolism
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16
Q

What allows the removal of an electron from NADPH?

A

p450 OxidoReductase (POR)

17
Q

POR effects

A
steroid synthesis in adrenal glands and gonads 
Cholesterol synthesis 
Metabolism in the liver of:
- steroids
- drugs 
- other xenobiotics
18
Q

What is the main type of p450 nomenculture?

A

CYP2

19
Q

Type of anti-histamine drug

A

Terfenadine

20
Q

Type of antidepressant

A

Amitriptyline

21
Q

Describe sulphotransferases

A
Phase 2 metabolism 
Conjugating moiety: sulphate 
Location: high concentrations in the liver and intestine and also found in platelets 
Subcellular location: cytosol 
Cofactors: PAPS
22
Q

Describe N-acetyl transferases

A

Phase 2 metabolism
Conjugating moiety: acetyl group
Cofactors: acetyl CoA
Mainly in the liver and in the gut and lung

23
Q

Describe UDP-glucuronyltransferases (UGT)

A

Conjugating moiety: glucuronic acid
Membrane bound protein
High concentrations in the liver, some in the gut and other tissues
Subcellular location: smooth endoplasmic reticulum
Cofactors: UDP-GA

24
Q

Why are glucuronide good in drug metabolism?

A

They are readily excreted

25
Q

What does the use of cytochrome p450 do to the drug?

A

Make electrophiles

26
Q

What does glutathione do to the electrophiles?

A

Make less toxic conjugates

27
Q

What catalysts the glutathione reaction?

A

Glutathione S-transferases (GST)

28
Q

What happens to the less toxic conjugates?

A

Excreted in urine or bile

Metabolised further in the mercapturic acid pathway

29
Q

Where are glutathione transferase found?

A
Cytoplasm 
Mitochondria 
Endoplasmic retriculum 
Nucleus 
In all tissues and eukaryotes
30
Q

Effects of oltipraz

A

Inhibit phase 1 p450 enzymes and induces phase 2 enzymes

31
Q

Effects of polymorphisms in drug metabolism

A

Mutations in genes for drug metabolising enzymes - leading to increased or decreased enzyme activity

32
Q

Describe a common food-drug interaction

A

Bananas and ACE inhibitors

  • ACE inhibitors increase potassium in your body
  • too much potassium can cause irregular heartbeat Andy heart palpitations
33
Q

Give the stages of drug development

A

1) target identification
2) target assay construction and screening
3) target validation
4) phase 1 safety
5) phase 2 efficacy safety
6) phase 3 efficacy safety
7) FDA review and approval

34
Q

How long does drug devlopment take

A

12-15 years

35
Q

Common effect of chemotherapy

A

Induces p450