Exam 1 - Metabolism and Excretion Flashcards

1
Q

redistribution

A

drug moves away from its site of action; reducing its active concentration at the target site

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2
Q

biotransformation (metabolism)

A

drugs are chemically alterd, usually in the liver, to inactive metabolites that are easier to excrete

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3
Q

What are the two major effects of biotransformation?

A
  1. usually converts substances to more hydrophilic compounds that are more readily excreted
  2. usually converts substances to compounds that are less pharmacologically active
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4
Q

What is Phase I of biotransformation?

A

introduction of small polar groups on the drug
* reaction classes: oxidations and hydrolysis
* product is usually more polar (hydrophilic)

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5
Q

Phase I oxidations

A
  • mixed functions oxidases
  • monoamide oxidases
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6
Q

explain the reaction of mixed function oxidases

A

drug + oxygen molecule –> drug-OH + water
* cytochrome P450s or CYPs
* metabolize wide variety of xenobiotics and endogenous compounds

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7
Q

explain CYPs

A
  • 3 families: CYP1, CYP2, CYP3
  • each family has subfamilies
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8
Q

explain the reaction of monoamine oxidases

A

monoamine (NH2) drug + oxygen molecule –> drug metabolite
* mainly impacts drugs affecting neurotransmission

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9
Q

Phase I hydrolysis

A

cholinesterases (add a water)
* acetylcholinesterase
* plasma cholinesterase

  • differ in molecules they prefer to metabolize
  • differ in location in the body
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10
Q

What is Phase II of biotransformation?

A

adding a larger polar molecule (glucuronic acid, sulfate) to a hydroxyl (-OH) group on the drug
* reaction classes: transferases
* products usually very polar

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11
Q

Phase II enzymes

A
  • glucuronyl transferases (UGTs)
  • sulfotransferases (STs)
  • catechol-O-methyltransferase (COMT)
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12
Q

glucuronyl transferases (UGTs) reaction

A

drug-OH + activated glucose –> drug-glucuronide

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13
Q

sulfotransferases (STs) reactions

A

drug-OH + activated sulfate –> drug-sulfate

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14
Q

catechol-O-methyltransferase (COMT) reactions

A

mainly impacts monoamine drugs affecting neurotransmission

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15
Q

active metabolite

A

drug metabolite that has significant activity (sometimes greater than parent compound)

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16
Q

prodrug

A

inactive or relatively inactive precursor that is converted to a more active compound

17
Q

reactive metabolite

A

very toxic compound produced by biotransformation of a relatively inert substance (often reacts with protein or DNA)

18
Q

Where are common sites of biotransformation?

A

liver, GI tract, lungs, skin, kidneys, plasma

19
Q

Inhibitors of drug metabolism

A
  • imidazoles
  • macrolide antibiotics
  • bioflavonoids (grapefruit)
20
Q

What are important points about drug metabolism inhibitors?

A
  • decreased metabolism leads to increased drug levels
  • each inhibtors affects different CYPs
  • common site of drug-drug interaction
21
Q

factors influencing drug metabolism

A
  • genetic (pharmacogenetics)
  • disease states
22
Q

pharmacogenetics

A

the study of how an individual’s genetic makeup influences their response to drugs

23
Q

excretion

A

the drug and its metabolites are removed from the body; primarily through the kidneys or the liver

24
Q

What will a deficiency in an excretion route result in?

A

increased plasma concentration with subsequemt enhanced drug effects, unless the drequency or dose of a drug administered is reduced

25
What is the site of filtration in the kidneys?
the glomerulus * drugs move from blood into kidney (renal) tubules along with rest of blood contents
26
processes involved in drug excretion
* filtration (aqueous diffusion) * passive diffusion * carrier transport (transporters)
27
What are the limitations of the kidneys?
* drug size * protein bound drug
28
Where does filtration occur in the kidneys?
the glomerulus
29
Where does carrier transport happen in the kidneys?
mainly in the proximal tubule
30
Where does passive diffusion occur in the kidneys?
at any point along the tubule