Toxicokinetics Flashcards

1
Q

Toxicokinetics

A

Study of the absorption, distribution, biotransformation, and excretion of toxic agents

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2
Q

Drug disposition

A

Study of the movement of drugs in the body across biological membranes from the time of absorption until elimination

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3
Q

What is it the most common route of exposure in toxicology?

A

Oral route

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4
Q

What are the 4 stages of drug distribution?

A

Absorption
Distribution
Biotransformation
Excretion

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5
Q

What is passive diffusion?

A

Transmembrane and paracellular movement

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6
Q

What is transmembrane passive diffusion?

A

The movement of water through aqueous protein channels or by flow resulting from osmotic or hydrostatic differences across the membrane

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7
Q

What is paracellular passive diffusion?

A

Transport of water is through intercellular aqueous pores

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8
Q

What is simple diffusion?

A

Bulk flow of water can carry with it small water soluble substances

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9
Q

What is facilitated diffusion?

A

A carrier mediated transport that DOES NOT NEED energy; a drug moves from high conc to low conc

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10
Q

What is active transport?

A

A carrier mediated transport that REQUIRES energy; drug moves across membrane from low conc to high
conc

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11
Q

In primary active transport, where does the energy come from?

A

Directly from ATP such as the Na/K ATPase

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12
Q

In secondary active transport, where does the energy come from?

A

Uses stored energy in the Na electrochemical gradient that was created using ATP in primary active transport

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13
Q

Pinocytosis

A

Specific type of endocytosis where the cell engulfs the drug molecules dissolved in water

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14
Q

Concentration gradient

A

In simple diffusion drugs move from high conc to low, in active transport drugs move from low to high which is why they require energy

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15
Q

Explain the relationship between lipid solubility and speed of crossing the membrane

A

The higher the lipid solubility of the drug, the faster it crosses the membrane

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16
Q

How is lipid solubility measured?

A

By the lipid partition coefficient (ratio between solubility of drug in lipid admits solubility in water)

17
Q

Drugs cross biological membranes in the ___________________ form.

A

Non-ionized (lipid soluble, don’t carry electric charge)

18
Q

The rate of diffusion depends on what?

A

Ratio between non-ionized and ionized form of the drug (N/I)

19
Q

What 3 things does the ionization of a drug depend on?

A

The pH of the drug
The pKa of drug
The pH of the medium

20
Q

What is the pKa of a drug?

A

The pH as which a weak electrolyte is 50% ionized and 50% non-ionized

21
Q

Most drugs are ______________ (weak or strong) electrolytes.

A

Weak

22
Q

Acidic drugs ionize in __________ medium and basic drugs ionize in __________ medium

A

Alkaline; acidic