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Principles of Drug and Hormone Action > drug metabolism > Flashcards

drug metabolism Flashcards

1
Q

pH equation

A

-log10[H+]

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2
Q

physiological pH

A

7.4

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3
Q

what happens to amino acids at physiological pH?

A

protonated at the amine group

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4
Q

what proteins can the kidney filter out?

A

xenobiotics

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5
Q

xenobiotics definition

A

proteins found in plants that the kidney can filter out

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6
Q

metabolism function

A

inactive and excrete xenobiotics

go from non polar molecules to polar ones

tag molecules so that the body can recognise them

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7
Q

what occurs in phase 1?

A

introduce or reveal a functional group by hydroxylation, oxidation, reduction or hydrolysis

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8
Q

what occurs in phase 2?

A

conjugate to a polar molecule such as glucuronate, sulfate, glycine and glutathione

allows a point of attack for conjugating systems

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9
Q

where does phase 2 take place?

A

liver primarily

GI, kidney and lungs

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10
Q

why are nonpolar drugs not excreted?

A

able to diffuse across the bilayer of the nephron epithelia, so they become reabsorbed easily

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11
Q

problem with phase 1 reactions?

A

products are often more chemically active and thus are more toxic

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12
Q

oxidation reaction definition

A

adding oxygen which results in a change within the chemical substance

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13
Q

reduction reaction definition

A

removal of oxygen

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14
Q

what may the activation of xenobiotics result in?

A

formation of carcinogens

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15
Q

prodrug definition

A

medication that becomes active once metabolised

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16
Q

important enzymes in phase 1

A

cytochrome P450 and monoamine oxidase

17
Q

explain cytochrome P450 action

A

aliphatic hydroxylation, replacing CH with CO

oxidises hydrocarbons to form an alcohol and water

mixed function oxidase, will oxidise any tagged molecule

18
Q

explain monoamine oxidase action

A

oxidise nitrogen on the monoamines to form aldehyde intermediates and ammonia

oxidative deamination

19
Q

phase II general product properties

A

increased molecular weight

less active than substrates

polar metabolites- water soluble

20
Q

where is alcohol metabolised in the body? + why

A

liver

has a high concentration of enzymes

21
Q

brief stages of alcohol breakdown

A

ethanol–> acetaldehyde –> acetic acid and acetyl- CoA

22
Q

phase I in alcohol metabolism

A

ethanol is oxidised to acetaldehyde using NAD+ and alcohol dehydrogenase

23
Q

how is alcohol metabolised in a fetus + why?

A

alcohol dehydrogenase is not yet fully developed

alcohol metabolism depends on cytochrome P450

24
Q

phase II in alcohol metabolism

A

acetaldehyde dehydrogenase catalyses the oxidation of acetaldehyde to acetic acid

25
Q

why is phase II important?

A

aldehydes are highly unstable compounds that form free radical structures which are highly toxic

lead to the damage of neural crest cells and can cause severe birth defects

can cause severe liver and kidney disease

26
Q

alcohol side effects

A

hypoglycaemia, lactic acidosis, hyperuricaemia

27
Q

hypoglycaemia explained

A

alcohol contains sugars, leading to an increase in insulin secretion, which leads to low blood glucose

also impairs gluconeogenesis

28
Q

lactic acidosis explained

A

ethanol is metabolised using NAD to form NADH

high levels of NADH inhibit the glycolysis pathway, to prevent too much glucose being broken down

this diverts the pyruvate metabolism towards lactate

29
Q

hyperuricaemia definition

A

excess uric acid in the blood

30
Q

what does the amount of urate depend upon?

A

balance between the amount of purines eaten in food, and urate synthesised by the body and the amount of urate excreted in urine or through the GI tract

31
Q

explain alcoholic hyperuricaemia

A

ethanol increases uric acid by increasing lactic acid production

32
Q

how may alcohol cause paracetamol toxicity?

A
  1. alcohol presence induces transcription of more cytochrome P450
  2. more cytochrome P450 will oxidise paracetamol
  3. 10% of the products are quinoneimine which is a hot electrophile which can cause cell death and organ failure
33
Q

explain metabolism of paracetamol

A
  1. paracetamol does not undergo phase I, as it already has a polar hydroxyl group
  2. tagged with glucuronate or sulfate which is then urinated out
  3. 10% is oxidised by CYP2E1 to form an electrophile
34
Q

why is paracetamol overdose dangerous?

A

large quantity of quinoneimine in the liver

will link sulfhydryls, crosslinking proteins resulting in coagulation

Principles of Drug and Hormone Action (10 decks)

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