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Pharmacology > Pharm 5 - Drug Metabolism > Flashcards

Pharm 5 - Drug Metabolism Flashcards

1
Q

What does metabolism tend to do to a drug?

A

eliminate or reduce the pharmacological activity of a drug

makes the drug more polar and soluble so it can be excreted easily

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2
Q

What is hepatic first pass metabolism?

A

Metabolic conversion of the drug into something different before it enters the circulation

the effect of the drug first time it goes into the liver

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3
Q

What effect does extensive first pass metabolism have on bioavailability?

A

extensive first pass metabolism = low bioavailability

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4
Q

How can you avoid hepatic first pass metabolism?

A

Give a drug IV

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5
Q

What are the three types of reactions that fall under Phase 1 reactions?

A

Oxidation
Reduction
Hydrolysis

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6
Q

What is the purpose of Phase 1 metabolism?

A

To create or unmask functional groups which can be used in Phase II reactions

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7
Q

How do Phase 1 reactions affect polarity of the drug?

A

little effect on polarity

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8
Q

Which enzyme system is important to drug metabolism?

A

Cytochrome p450

Family of 57 enzymes found in liver

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9
Q

What are the substrates of the cytochrome p450 mediated oxidation reaction?

A

drug, NADPH, oxygen and protons

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10
Q

What are the products of the cytochrome p450 mediated oxidation reaction?

A

hydroxylated drug, NADP+, water

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11
Q

Describe the oxidation cycle of cytochrome p450.

A
  • Drug binds to the iron in cp450
  • electron from NADPH is picked up by Fe3+ iron, making it Fe2+ iron
  • Fe2+ gives the electron to oxygen making it unstable

This happens again

  • so oxygen is now O2- and very unstable.
  • hydroxylated drug + water released
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12
Q

What is N-demethylation? And what does its reaction produce?

A

oxidation of a methyl group in a nitrogen environment

produces a formaldehyde - HCHO

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13
Q

What does N-demethylation do to a drug?

A

removes the pharmacology of a drug

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14
Q

What is O-demethylation?

A

Oxidative attack of P450 on methyl group attached to oxygen

Converts oxygen to hydroxyl group and releases formaldehyde

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15
Q

What is N-oxidation? Describe the type of bond formed?

A

oxidation of the nitrogen group itself
Nitrogen has 2 free electrons to form a dative bond with water
generates an amino acid

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16
Q

What enzyme catalyses the N-oxidation reaction?

A

Flavin containing monooxygenase

17
Q

Describe a condition involving this enzyme.

A

Flavin containing monooxygenase deficiency - Fish odour syndrome

People without this enzyme cannot convert trimethylamine, so it stays and it is foul smelling

18
Q

Describe alcohol oxidation.

A

Alcohol is first converted to acetaldehyde by alcohol dehydrogenase.
Then converted to acetic acid

19
Q

Where in the cell are flavin containing monooxygenase and CP450 found?

A

Endoplasmic reticulum

20
Q

Where is alcohol dehydrogenase found?

A

Cytoplasm

21
Q

Where do reduction reactions tend to take place and why?

A

GI tract as low oxygen environment

22
Q

State 2 types of hydrolysis enzymes?

A

Esterases and Amidases

23
Q

Name 6 types of Phase II reactions.

A 
Glucuronidation
Acetylation
Sulphation
Methylation
Amino acid conjugation
Glutathione Conjugation
24
Q

How do you get the name of the enzyme for each Phase II reaction?

A

add transferase to the end

25
Q

What effect do phase II reactions have on the drugs?

A

make drugs more polar and water soluble so they can be excreted more easily

26
Q

What is the most common phase II reaction?

A

Glucuronidation - addition of a sugar to a molecule

27
Q

What is the importance of glutathione conjugation?

A

conjugated with electrophiles so they are excreted

electrophiles are damaging to DNA, often generated during metabolism

28
Q

State a conjugating agent used for glucuronidation

A

UDPGA

29
Q

State an important property of the conjugates formed from glucuronidation and its impact on its excretion.

A

large molecular weight products so cannot be be filtrated via glomerulus

excreted in bile

30
Q

What is the conjugating agent in acetylation and what is the product?

A

acetyl choline

product = acetylated derivative of the drug

31
Q

What is the conjugating agent for methylation?

A

S-adenosyl

32
Q

What effect does methylation have on polarity?

A

Decreases polarity

33
Q

What is the conjugating agent used in salphation?

A

PAPS -

34
Q

What are the properties of the derivative formed in sulphation?

A

sulphuric acid derivative of the drug

very polar and very soluble

35
Q

What type of molecule is glutathione?

A

Tripeptide consisting of glycine, glutamine, cysteine

36
Q

What effect does drug metabolism have on biological half life, duration of expose, and accumulation of drugs in the body?

A

Decreases ALL

Pharmacology (10 decks)

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