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Drug metabolism/ detox mechanisms > Principles > Flashcards

Principles Flashcards

1
Q

define pharmacodynamics

A

what a drug does to the body

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2
Q

define pharmacokinetics

A

what the body does to a drug

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3
Q

ADME

A

adsorption, distribution, metabolism and excretion

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4
Q

goal of drug metabolism

A

inactivate and excrete xenobiotics

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5
Q

phase 1 function

A

introduce of reveal a functional group for phase 2

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6
Q

phase 2 function

A

conjugate to a polar molecule

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7
Q

where drug metabolism occurs

A

primarily liver, then GI, kidney and lungs

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8
Q

functions of metabolism

A

want to take a non-polar compound and make it more polar - so add functional group and then conjugate it to make it more polar, as non-polar molecules cannot pass out of the renal tubule

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9
Q

phase 1 type of reaction

A

usually oxidation (most common)

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10
Q

types of phase 1 enzymes

A

monooxygenases (specific enzymes) eg. alcohol dehydrogenase and MAO
mixed function oxidase (general enzyme family) eg. cytochrome P450, will oxygenate any unknown compound

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11
Q

process of oxidative deamination

A

Monoamine oxidase
Acts on molecules such as catecholamines (common neurotransmitter)
removes amine group, produces an aldehyde and ammonia

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12
Q

cytochrome P450 action

A

replaces C-H with C-O(at physiological pH and temp)
aliphatic hydroxylation from saturated hydrocarbon to an alcohol and water, uses NADPH as electron donor
can also do aromatic hydroxylation to oxidise benzene

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13
Q

what is cytochrome P450

A

superfamily of enzymes with overlapping specificities, however the largest group of enzymes is to oxidise large non-polar molecules
mixed-function oxidases

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14
Q

case study - toxicity in paracetamol metabolism

A

metabolism in overdose makes paracetamol toxic
can be oxidised by offing glucuronate or sulphate to make it more soluble
if in excess, 10% can be metabolism by a cP450 enzyme, can make a quinoneimine (very reactive) and result in cell death - hepatotoxicity
shows that drug metabolites may be toxic

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15
Q

another action of cP450

A

inducible in the liver, eg. can increase or decrease transcription if consuming lots of specific metabolites

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16
Q

phase 2 metabolism action

A

addition of polar groups
eg. glucuronic acid, glycine, glutathione, sulphate
incorporated by oxidation/ reduction reactions to increase solubility

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17
Q

alcohol metabolism process

A

ethanol -> acetaldehyde -> acetic acid
aldehydes are very toxic, can cross-link proteins
alcohol dehydrogenase and aldehyde dehydrogenase enzymes
(aldehyde dehydrogenase deficiency associated with asian flushing syndrome)

18
Q

what does chemical modification do?

A

usually abolishes activity

19
Q

another reaction of drug metabolism

A

hydrolysis, eg. acetylcholinesterase

20
Q

glomerular filtration of drugs

A

most filtered freely, unless bound to serum proteins

filtered drugs either passively reabsorbed to trapped in urine depending on lipid solubility and tendency to ionise

21
Q

other form of renal excretion

A

tubular secretion and reabsorption, eg. the active secretion of penicillin

22
Q

drug-drug interactions

A

drugs can alter the pharmacokinetics of another drug
enzymes can be induced by different compounds
eg. ethanol can induce cP450 systems to increase metabolism and potential toxicity of other compounds

23
Q

other actions of phase 1

A

can activate pro-drugs

can transform innocuous substrate into chemically reactive, toxic metabolite

24
Q

factors affecting alcohol metabolism

A 
conc, of alcohol
blood flow at site of absorption
irritant properties of alcohol
rate of ingestion 
fed/ fasted state
25
Q

metabolic effects of alcohol

A

hypoglycaemia
lactic acidosis
hyperuricaemia

26
Q

phase 1 alcohol metabolism

A

in liver
produces acetaldehyde
alcohol dehydrogenase enzyme in cytosol or P450 enzyme in ER or catalase in peroxisomes

27
Q

aldehyde dehydrogenase

A

major enzyme
uses NAD+
in cytosol., highest conc, in liver

28
Q

effect of alcohol on plasma glucose

A

impairs cognitive function and hypoglycaemia awareness
glujconeogeneis impaired
impairs growth hormone, may reduce insulin sensitivity

29
Q

phase 2 alcohol metabolism

A

aldehyde dehydrogenase

mostly in mt

30
Q

toxic effect of aldehyde

A

mt dysfunction
lipid peroxidation
increased collagen synthesis
decreased microtubule function, altered transport and secretion

31
Q

drug-drug interactions

A

drugs can alter the pharmacokinetics of another drug
enzymes can be induced by different compounds
eg. ethanol can induce cP450 systems to increase metabolism and potential toxicity of other compounds

32
Q

other actions of phase 1

A

can activate pro-drugs

can transform innocuous substrate into chemically reactive, toxic metabolite

33
Q

factors affecting alcohol metabolism

A 
conc, of alcohol
blood flow at site of absorption
irritant properties of alcohol
rate of ingestion 
fed/ fasted state
34
Q

metabolic effects of alcohol

A

hypoglycaemia
lactic acidosis
hyperuricaemia

35
Q

phase 1 alcohol metabolism

A

in liver
produces acetaldehyde
alcohol dehydrogenase enzyme in cytosol or P450 enzyme in ER or catalase in peroxisomes

36
Q

aldehyde dehydrogenase

A

major enzyme
uses NAD+
in cytosol., highest conc, in liver

37
Q

effect of alcohol on plasma glucose

A

impairs cognitive function and hypoglycaemia awareness
glujconeogeneis impaired
impairs growth hormone, may reduce insulin sensitivity

38
Q

phase 2 alcohol metabolism

A

aldehyde dehydrogenase

mostly in mt

39
Q

toxic effect of aldehyde

A

mt dysfunction
lipid peroxidation
increased collagen synthesis
decreased microtubule function, altered transport and secretion
- acetaldehyde can react spontaneously with amino groups of lysine in proteins

40
Q

effect of drugs binding to plasma proteins

A

reduces free drug available to diffuse into tissue fluid, reduces renal clearance of drugs

41
Q

carrier mediated distribution of drugs

A

uptake of some drugs futon the gut and excretion into bile and urine

Drug metabolism/ detox mechanisms (4 decks)

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