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Drugs and Toxicology > Lecture 4B: Toxicokinetic > Flashcards

Lecture 4B: Toxicokinetic Flashcards

1
Q

Physiochemical Factors

A
  • Lipid Solubility/hydrophobicity
  • Degree of ionization
  • Size/Shape
  • Charge/polarity
  • Structure similarly to endogenous molecules
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2
Q

Four Phases

A

– Absorption
– Distribution
– Metabolism (Biotransformation)
– Excretion

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3
Q

Toxicokinetics (TK)

A

The study of how the body treats toxins/toxicants that enter and the factors that may influence the concentration of a toxin at its site of action.

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4
Q

Xenobiotic

A

This is any foreign substance that is present in the body.

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5
Q

Target Site/Organ

A

the site/organ on which the toxin/toxicant elicit its toxic effect.

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6
Q

After absorption lead enters the blood and ___ is taken up by red blood cells (RBCs).

A

97%

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7
Q

What is the half (½) life of lead?

A

2-3 weeks

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8
Q

What happens during the half life?

A

there is redistribution to liver and kidney, then excretion into bile or deposition into bone.

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9
Q

After an initial, reversible uptake into bone, lead in the bone will

A

become incorporated into the hydroxyapatite crystalline structure

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10
Q

Past exposure to lead can be detected via _____ and ___.

A

X-ray analysis and blood and urine analysis.

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11
Q

How does lead become detectable in blood & urine analysis?

A

The amount in blood representing current exposure.

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12
Q

Organs and systems destroyed by lead

A

kidney, testes, bones, gastrointestinal tract and
the nervous system.

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13
Q

Lead causes significant biochemical effects like

A

Being the interference with haem-synthesis giving rise to anemia

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14
Q

Acute exposure to inorganic lead results to

A

renal damage particularly to the proximal tubules

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15
Q

Lead adversely affects

A

reproductive function in both males and females

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16
Q

Treatment/Detection of Lead

A
  • X ray to detect or blood/urine test then -
  • Bowel irrigation polyethylene glycol solution
  • Gastric lavage
  • Chelation therapy- bind to lead then excreted in urine
  • Activated charcoal – bind to lead in GI then administer cathartics
  • EDTA- Ethylenediaminetetracetic acid
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17
Q

What is a cell membrane?

A

The structure called the phospholipid bilayer, which is amphiphilic.

18
Q

Xenobiotics pass through cells located

A

at the sites of various routes to ultimately reach the target site.

19
Q

The cell membrane contains ______ heads and ______ tails.

A

hydrophilic and hydrophobic

20
Q

The heads of the cell membrane are turned

A

outwards, facing the extracellular environment.

21
Q

The tails of the cell membrane are turned

A

inwards to the intracellular environment.

22
Q

The membrane also contains important proteins called

A

transverse proteins

23
Q

Transverse proteins aid in

A

the transport of substances

24
Q

Two modes of Transport in cell membrane

A

Passive and Special Transport

25
Q

Types of Passive Transport

A

Filtration & Simple Diffusion

26
Q

Types of Special Transport

A

Active transport & Facilitated Diffusion

27
Q

What is an ion pump?

A

An enzyme that uses ATP to move ions across the cell membrane

28
Q

What is ion gates?

A

flow of ion across cell membrane

29
Q

Passive Transport

A

The movement of substances (toxins/toxicant) across a cell membrane without the use of energy by the cell

30
Q

Filtration

A

The passage of molecules from one environment to another through a porous membrane due to osmotic pressure or hydrostatic forces.

31
Q

Simple Diffusion

A

movement of a solute from an area of high concentration to an area of low concentration

32
Q

The lipid solubility of larger compounds will determine

A

the rate of transport across the membrane.

33
Q

What factors that must be met for simple diffusion:

A
  1. There most be a concentration gradient
  2. Must be lipid soluble
  3. Must be non-ionized
34
Q

Only _______ will go down the concentration gradient.

A

non-ionized lipid soluble compounds

35
Q

Partition Coefficient refers to

A

the solubility of a compound between two immiscible environments.

36
Q

Positive co efficient values are associated with

A

high lipid solubility

37
Q

Negative values co efficient are associated with

A

low lipid solubility

38
Q

More positive Partition Co-efficient are

A

more lipophilic

39
Q

Degree of Ionization

A

Many compounds/chemicals are weak acids or bases. This also applies to toxins/toxicants.

40
Q

The ionized form of a toxin usually has

A

low lipid solubility

41
Q

Why is degree of ionization important?

A

This determines the extent of absorption, as only the non-ionized form will be able to pass through the lipid bilayer by passive diffusion.

42
Q

Toxins/Toxicants low in lipid solubility may cross the cell membrane, but at

A

slow inefficient rates. This would aid in preventing a toxic effect.

Drugs and Toxicology (14 decks)

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