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FPT > Pharmacokinetics Principles 3 (metabolism and excretion) > Flashcards

Pharmacokinetics Principles 3 (metabolism and excretion) Flashcards

1
Q

chemical alteration of the drug in the body

A

biotransformation (metabolism).

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2
Q

transformation in biological system

A

biotransformation

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3
Q

in which order of kinetics the rate of elimination depends on dose

A

first order

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4
Q

in which order of kinetics the rate of elimination does not depends on dose

A

zero order kinetics

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5
Q

list the 4 steps of metabolism

A

1- converts non polar (lipid soluble) substances.
2- to polar (lipid insoluble) substances.
3- no reabsorption in renal tubules.
4- excretion in urine.

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6
Q

if drug A is active, and the product B is inactive.
metabolism in this case ___________

A

stops drug action

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7
Q

if drug A is active, and the product B is active.
metabolism in this case ___________, and name an example of a drug.

A

action is prolonged.
eg, diazepam.

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8
Q

if drug A is inactive, and the product B is active.
metabolism in this case ___________

A

activates the drug after we reach the action site.

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9
Q

few drugs are inactive and need conversion in the body to one or more active metabolites, such drugs are called _________

A

prodrug.

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10
Q

give an example of a prodrug?

A

like in parkinson’s, dopamine cannot cross the BBB so we give Levodopa

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11
Q

what are the 2 reactions of biotransformation

A

1- phase 1, non-synthetic, functionalization reactions.
2- phase 2, synthetic, conjugation.

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12
Q

what happens to lipophilic drugs in phase one of biotransformation?

A

gets converted to polar molecules.

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13
Q

metabolites in phase one of biotransformation are ________ (active, inactive)?

A

may be active or inactive.

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14
Q

what is conjugated to drug metabolites in phase 2?

A

endogenous radical

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15
Q

metabolites in phase two of biotransformation are ________ (active, inactive)?

A

mostly inactive.

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16
Q

what are the 5 reaction in phase 1?

A

1- oxidation.
2- reduction.
3- hydrolysis.
4- cyclization.
5- decyclization.

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17
Q

what is the most common reaction in phase 1?

A

oxidations.

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18
Q

the oxidation reaction in phase 1 is mostly carried out by _____ in the ________

A

monooxygenases (cytochrome P450),
in the liver.

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19
Q

in oxidation reactions of phase one we either add ________ or remove ________ ?

A

add oxygen/ negatively charged molecules.
or
remove hydrogen/ positively charged molecules.

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20
Q

name 3 examples of oxidation reactions?

A

1- hydroxylation.
2- dealkylation.
3- oxidative deamination.

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21
Q

name 2 examples of a monooxygenases in the liver?

A

1- cytochrome P450
2- CYP3A4

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22
Q

_________ carries out metabolism of largest number of drugs.

A

CYP3A4

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23
Q

In reduction reactions of phase one we either add______ or remove______?

A

add hydrogen or remove oxygen.

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24
Q

give an example of reduction reactions

A

levodopa reduced to dopamine in the brain.

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25
Q

what enzyme reduces levodopa to dopamine?

A

dopa decarboxylase.

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26
Q

in hydrolysis reactions of phase one we add ______ in the presence of ______ such as, ______

A

add water molecules in the presence of enzymes such as esterase and amidase.

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27
Q

list the 4 drugs that undergo hydrolysis?

A

1- procaine.
2- aspirin.
3- pethidine.
4- succinylcholine.

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28
Q

what is the most important synthetic reaction?

A

glucuronide conjugation.

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29
Q

glucuronide conjugation is carried out by which enzyme?

A

UDP-glucuronosyl transferase (UGTs).

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30
Q

gray baby syndrome is caused by a deficiency of which enzyme?

A

glucuronyl transferase enzyme.

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31
Q

gray baby syndrome is caused by the usage of which drug?

A

chloramphenicol use.

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32
Q

list the 7 drugs that undergo glucuronide conjugation?

A

1- chloramphenicol.
2- aspirin.
3- paracetamol.
4- morphine.
5- PABA.
6- diazepam.
7- digoxin.

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33
Q

list the 3 endogenous substances that undergo glucuronide conjugation?

A

1- bilirubin.
2- sex steroids.
3- thyroxine.

34
Q

when _____ combines with paracetamol it turns it into harmless products

A

glutathione

35
Q

in the case of paracetamol poisoning, ________ supply falls short and is unable to convert it to harmless products.

A

glutathione.

36
Q

give examples of microsomal enzymes?

A

monooxygenases, cytochrome P450, UGTs

37
Q

where are microsomal enzymes located?

A

smooth endoplasmic reticulum, in the liver, kidney and intestines.

38
Q

drugs that increase activity of microsomal enzymes and increase the metabolism of other drugs or the same drug itself

A

liver microsomal enzymes inducers.

39
Q

drugs that decrease activity of microsomal enzymes and decrease the metabolism of other drugs or the same drug itself

A

liver microsomal enzymes inhibitors.

40
Q

list 6 examples of microsomal enzyme inhibitors?

A

1- allopurinol.
2- erythromycin.
3- ketoconazole.
4- cimetidine.
5- HIV protease inhibitors.
6- grape juice.

41
Q

list 3 examples of microsomal enzyme inducers?

A

1- anticonvulsants, rifampin induce CYP3A4.
2- isoniazid and alcohol induce CYP2E1.
3- polycyclic hydrocarbons in cigarette smoke, charcoal broiled meat induce CYP1A.

42
Q

the irreversible removal of drug from the body

A

elimination.

43
Q

what does elimination involve?

A

1- biotransformation (drug metabolism).
2- excretion.

44
Q

what are the 3 major routes of elimination?

A

1- hepatic metabolism.
2- biliary metabolism.
3- urinary metabolism.

45
Q

the volume of blood from which the drug id cleared per unit time?

A

clearance

46
Q

what are the 2 main routes of excretion?

A

1- renal excretion.
2- biliary excretion.

47
Q

what are the 5 minor routes of excretion?

A

1- pulmonary excretion.
2- salivary excretion
3- mammary excretion via milk.
4- skin / dermal excretion via sweet.
5- tears.

48
Q

what is the most important channel of excretion for majority of drugs?

A

renal elimination.

49
Q

what organ is responsible for excreting all water soluble substances?

A

the kidneys

50
Q

net renal exertion is expressed by?

A

(glomerular filtration + tubular secretion) - tubular reabsorption

51
Q

what are the 3 processes involved in renal elimination?

A

1- glomerular filtration.
2- tubular reabsorption.
3- tubular secretion.

52
Q

where are drugs and their metabolites can be excreted?

A

1- faeces.
2- exhaled air.
3- saliva and sweat.
4- milk.

53
Q

most of the drug in faeces is derived from what?

A

bile.

54
Q

the rate of elimination is directly proportional to drug concentration

A

first order kinetics.

55
Q

constant _______ of drug is eliminated per unit time in 1st order kinetics?

A

fraction

56
Q

in first order kinetics increase in does, ________ t1/2.

A

unalter

57
Q

what is the most common order of kinetics?

A

1st

58
Q

rate of elimination is not dependant on drug concentration

A

zero order kinetics.

59
Q

constant ________ of drug is eliminated per unit time in zero order kinetics?

A

amount

60
Q

increase in dose, ______ elimination in zero order kinetics.

A

does not increase.

61
Q

increase in dose, ______ t1/2 in zero order kinetics.

A

increases

62
Q

there is risk of toxicity in which order of kinetics?

A

zero order

63
Q

give examples of drugs that undergo zero order kinetics

A

ethanol, high doses of phenytoin.

64
Q

give examples of drugs that change from 1st order to zero order kinetics?

A
  • phenytoin.
  • tolbutamide.
  • theophylline.
  • warfarin.
65
Q

T 1/2 is ____ ______ to volume of distribution and ______ _______ to clearance.

A

directly proportional.
inversely proportional.

66
Q

rate of drug elimination equals rate of drug administration

A

steady state.

67
Q

how many half lives does it take to reach steady state?

A

4-5 T1/2

68
Q

Dosing rate is expressed by

A

DR = (C)(CL) / F
F = bioavailability
CL = clearance
C = target plasma concentration

69
Q

loading rate is expressed by

A

LD = Vd (C) / F
Vd = volume of distribution
C = clearance.
F = bioavailability.

70
Q

dose required to maintain Css

A

dosing rate

71
Q

administered to achieve the desired plasma level rapidly.

A

loading dose

72
Q

the measurement of plasma concentration of drugs

A

therapeutic drug monitoring (TDM)

73
Q

what are the 6 uses of TDM?

A

1- drugs with low safety margin.
2- if individual variations are large.
3- potentially toxic drugs used in the presence of renal failure.
4- in cases of poisoning.
5- in cases of failure of response without any apparent reason.
6- check patient compliance.

74
Q

give example of drugs with low safety margin?

A
  • digoxin.
  • anticonvulsants.
  • antiarrhythmics.
  • theophylline.
  • aminoglycoside ABx.
  • lithium.
75
Q

give example of drugs with individual variation are large?

A
  • antidepressants.
  • lithium.
76
Q

give example of drugs with potentially toxic drugs used in the presence of renal failure?

A
  • aminoglycoside antibiotics.
  • vancomycin.
77
Q

give example of drugs with failure of response without any apparent reason?

A

antimicrobials.

78
Q

give example of drugs that need to be check for patient compliance?

A
  • psychopharmacological agents.
79
Q

what are the 3 cases where TDM is of no value?

A

1- drugs whose response is easily measurable.
2- drugs that get activated in the body.
3- drugs with irreversible action.

80
Q

give example of drugs whose response is easily measurable?

A

antihypertensives

81
Q

give example of drugs that get activated in the body?

A

levodopa.

82
Q

give example of drugs with irreversible action?

A

organophosphates.

FPT (17 decks)

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