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FPT > Pharmacokinetics Principles 2 (absorption and distribution) > Flashcards

Pharmacokinetics Principles 2 (absorption and distribution) Flashcards

1
Q

list the 4 steps of pharmacokinetics?

A

1- absorption.
2- distribution.
3- metabolism.
4- excretions.

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2
Q

the transfer of a drug from the site of administration to the blood stream

A

absorption of drugs.

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3
Q

absorption depends on 2 factors, what are they?

A

1- drug’s chemical characteristics.
2- route of drug administration.

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4
Q

what is the most importants site of absorption for orally administered drugs?

A

small intestine.

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5
Q

bioavailability for I.V delivery is ___%

A

100%

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6
Q

for absorption to happen drugs need to cross _______

A

biological membranes.

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7
Q

list the 4 mechanisms of absorption

A

1- passive diffusion.
2- facilitated diffusion.
3- active transport.
4- endocytosis and exocytosis.

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8
Q

in passive diffusion drugs move ____ (along, against) the concentration gradient?

A

along.
from higher conc. to lower conc.

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9
Q

which mechanisms of absorption don’t need energy?

A

passive diffusion and facilitated diffusion.

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10
Q

which mechanism of absorption is not saturable?

A

passive diffusion.

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11
Q

in facilitated diffusion carrier proteins undergo which type of change to transport drugs?

A

conformational change.

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12
Q

in facilitated diffusion, drugs move ____ (along, against) conc. gradient.

A

along the conc gradient, higher to lower.

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13
Q

which mechanisms of absorption are saturable?

A

facilitated diffusion and active transport.

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14
Q

facilitated diffusion is inhibited by drugs that ______ for the carrier.

A

compete.

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15
Q

in active transport, drugs move ____ (along, against) conc. gradient.

A

against.
lower to higher.

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16
Q

which mechanism of absorption is selective?

A

active transport.

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17
Q

active transport can be competitively ____ by other co-transported substances?

A

inhibited.

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18
Q

engulfment of the drug by the cell membrane and transport in the cell in a drug-filled vesicle.

A

endocytosis

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19
Q

endocytosis and exocytosis are used for the transport of drugs of ____ size across membranes

A

large.

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20
Q

_______ is absorbed by endocytosis from the GIT?

A

vitamin B12.

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21
Q

_________ are stored in vesicles and released by exocytosis?

A

neurotransmitters.

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22
Q

list the 5 factors affecting absorption?

A

1- pH.
2- blood flow to the absorption site.
3- total surface area available for absorption.
4- contact time at the absorption surface.
5- expression of P-glycoprotein.

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23
Q

ionized forms of drugs are _____ (lipid, water) soluble.

A

water

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24
Q

unionized forms of drugs are _____ (lipid. water) soluble.

A

lipid

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25
Q

__________ (ionized, unionized) form is better absorbed?

A

unionized.

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26
Q

A drug crosses biological membrane readily if it is ______

A

uncharged.

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27
Q

weak acids are unionized at _____ pH.

A

acidic

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28
Q

weak bases are unionized at ____ pH.

A

basic.

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29
Q

the pH at which the drug is 50% ionized

A

pKa of a drug.

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30
Q

the _____ pKa of a drug the more acidic it is

A

lower.

31
Q

give an example of an acidic drug that gets largely unionized at gastric pH

A

aspirin

32
Q

where are basic drugs absorbed from?

A

the intestine.

33
Q

greater the blood flow to the absorption site the ____ is the absorption

A

more

34
Q

shock ____ absorption from subcutaneous route.

A

decreases.

35
Q

greater the surface area. ____ is the absorption

A

more

36
Q

more is the contact time, _____ is the absorption

A

more

37
Q

in areas of high expression.P-glycoprotein ______ drug absorption.

A

reduces.

38
Q

P-glycoprotein is associated with what?

A

associated with multidrug resistance.

39
Q

where is P-glycoprotein expressed?

A

liver, kidneys, placenta, intestines, and brain capillaries.

40
Q

fraction of administered drug that reaches the systemic circulation in unchanged form

A

bioavailability

41
Q

bioavailability is important for calculating drug doses for which administration route?

A

non-intravenous.

42
Q

bioavailability of i.v given drug is ___%?

A

100%

43
Q

list the 4 factors affecting bioavailability?

A

1- first- pass hepatic metabolism.
2- solubility of drug.
3- chemical instability.
4- nature of drug formulation.

44
Q

bioavailability of penicillin and insulin when given orally is ___?

A

0%

45
Q

how does first pass metabolism affect bioavailability?

A

the amount of drug that reach the systemic circulation in unchanged form is decreased.

46
Q

90% of _____ (which drug?) is cleared during a single passage through the liver, which is why it is given through the ______ route.

A

nitroglycerine,
sublingual route.

47
Q

for a drug to be absorbed it must be ___ in aqueous solutions.

A

soluble

48
Q

drugs which are poorly soluble have ___ bioavailability.

A

low

49
Q

list the 4 factors that influence the ease of dissolution?

A

1- particle size.
2- salt form.
3- enteric coatings.
4- presence of excipients.

50
Q

2 related drug preparations are bioequivalent if the show _____________ and ____________________

A

complete bioavailability, and similar times to achieve peak blood concentration.

51
Q

the process by which a drug reversibly leaves the blood stream and the extracellular fluid and tissues

A

drug distribution

52
Q

list the 4 factors that affect drug distribution

A

1- differences in regional blood flow.
2- binding of drugs to plasma proteins and tissue proteins.
3- presence of tissue-specific transporters.
4- lipid solubility.

53
Q

what is the most common protein drugs bind to?

A

albumin

54
Q

redistribution happens only in ___ ____ soluble drugs.

A

highly lipid soluble drugs.

55
Q

give an example of a drug that undergoes redistribution

A

thiopentone sod.
an anaesthetic.

56
Q

the BBB limits the entry of _____ soluble drugs into the CNS.

A

non-lipid soluble drugs.

57
Q

inflammation of the meninges _____ permeability of the BBB

A

increases.

58
Q

acidic drugs bind to _____ (which protein?) and basic drugs bind to ______ (which protein?)

A

acidic = plasma protein.
basic = alpha 1 acid glycoprotein.

59
Q

highly protein-bound drugs are ___ acting.

A

long

60
Q

plasma protein binding is a ______ (reversible, irreversible) process

A

reversible.

61
Q

irreversible binding of drugs can result in ____.

A

toxicity.

62
Q

give an example of an irreversible binding of a drug that results in toxicity

A

the irreversible binding of paracetamol metabolites to the hepatocytes.

63
Q

most drugs bind to which protein?

A

albumin

64
Q

what is the most abundant plasma protein

A

albumin

65
Q

what is the major source of drug and prolongs its action or cause local drug toxicity?

A

tissue reservoir

66
Q

give an example of a drug that concentrates in tissues and can give drug toxicity?

A

tetracyclins

66
Q

give an example of a drug that concentrates in tissues and can give drug toxicity?

A

tetracyclines

67
Q

the volume that would accommodate all the drug in the body if the concentration throughout was the same as in plasma

A

apparent volume of distribution (Vd)

68
Q

list the 3 compartments that take up the drug once it enters the body?

A

1- plasma compartment.
2- extracellular fluid.
3- total body water.

69
Q

list the 6 factors that Vd depends on?

A

1- lipid solubility.
2- plasma protein binding.
3- tissue sequestration.
4- pKa of the drug.
5- age, sex, obesity, pregnancy.
6- diseases like CHF, uremia, cirrhosis.

70
Q

drugs with ___ (high,low) of distribution are not easily removed by dialysis in case of poisoning

A

high

71
Q

Vd is expressed by?

A

Vd= dose administered I.V / plasma concertation.

72
Q

if a drug has a large Vd, most of the drug is in the _____ space and is unavailable to the ____ organs.

A

extraplasmic space.
excretory,

73
Q

what does an extremely high Vd indicate?

A

that the drug is sequestered in some tissues.

FPT (17 decks)

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