Metabolism and Excretion Flashcards

1
Q

Define xenobiotics.

A

Compounds other than those with a well-defined physiological role

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2
Q

Give examples of xenobiotics.

A

Most drugs, natural and industrial contaminants, food additives, recreational drugs

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3
Q

Describe the three ways in which the body protects itself.

A

->body prevents drug from entering bloodstream e.g. blood brain barrier
->body can physically remove the drug e.g. unchanged drug may end up in bile or urine).
->body can subject xenobiotics to biotransformation with the aim that these products should be removed more rapidly than the parent (or unchanged) compound

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4
Q

Biotransformation involves the increase of what?

A

Polarity

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5
Q

What happens to absorption if the lipophilicity is reduced?

A

The molecule is much less likely to be reabsorbed in the kidney tubule or intestine.

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6
Q

les are more likely to be absorbed?

A

Small non-polar molecules

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7
Q

What happens to molecules after going through phase one of metabolism?

A

->excreted
or
->undergo phase two metabolism

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8
Q

What happens in phase 1 metabolism?

A

Creating a functional group or modifying an existing one.

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9
Q

What kind of reactions result in the creation of new functional groups?

A

Oxidation

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10
Q

What kind of reaction is involved in modifying an existing functional group?

A

Hydrolysis

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11
Q

Given an example of a chemical functional group

A

hydroxyl (-OH)
amino (-NH2)

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12
Q

Most of the oxidations of drugs involve which enzymes?

A

Enzymes from the cytochrome P450 family

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13
Q

Where can phase 1 metabolism take place?

A

-Liver
-Gut
-Small intestine
-Lungs
-Kidney

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14
Q

Why does phase one metabolism take places in the liver, gut, small intestine, kidney and lungs?

A

All directly exposed to the environment and so play a frontline role in trying to protect the body by minimising its exposure to xenobiotics.

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15
Q

Where in the cell do the reactions in phase 1 take place?

A

Mostly in the SER
Some in cytosol
Some in mitochondria

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16
Q

What is phase one intended to help to do?

A

Reduce toxicity

17
Q

In phase one, why is there sometimes no reduction to toxicity?

A

Some of the intermediates are highly electrophilic so an covalently modify macromolecules (adducts; proteins and DNA)

18
Q

What % of phase 1 metabolites are toxic?

A

7%

19
Q

Name some metabolites that are toxic.

A

Quinones and quinone analogues

20
Q

Where does phase two occur?

A

Liver

21
Q

Where in the liver does phase two occur?

A

Hepatocytes

22
Q

Describe the products of phase two compared to phase one.

A

Products are larger, more hydrophilic and therefore more likely to be excreted.
Less pharmologically active.

23
Q

What do the products of phase two tend to be?

A

Weak acids.

24
Q

What does an intake of warfarin lead to the activation of?

A

Carboxylation

25
Q

How does warfarin work?

A

Blocks vitamin K recycling preventing blood clots from forming.

26
Q

Define elimination in terms of excretion.

A

Elimination is the final, irreversible removal of drug from the body.

27
Q

Define excretion.

A

The rate at which a drug is removed from the body

28
Q

What is clearance?

A

The volume of plasma from which the drug would be totally removed per unit time.

29
Q

Where does active renal secretion take place?

A

Proximal tube mainly

30
Q

What does active renal secretion do?

A

Can clear drugs too large to filter

31
Q

Is tubular reabsorption passive or active?

A

Passive

32
Q

What happens as kidneys get older?

A

Clearnace is reduced w a risk of toxicity

33
Q

What factors are required for hepatic clearance?

A

Requires good blood flow to the liver
Drug must be free (idk what this means either)