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Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

what are the 4 primary actions of the body on the drug?

A
  1. absorption
  2. distribution
  3. metabolism
  4. excretion
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2
Q

define absorption

A

process of unchanged drug moving from site of administration to site of measurement within the body

usually the peripheral venous circulation

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3
Q

what are the 5 primary processes that can influence the absorption of a drug?

A
  1. dose
  2. dosage form
  3. route of administration
  4. drug’s physicochemical properties
  5. A&P @ site of absorption
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4
Q

describe some characteristics of membrane permeable drugs

A
  • non-polar
  • lipid soluble
  • low MW
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5
Q

explain the mode of transportation of drugs that are not
- non-polar
- lipid soluble
- low MW

A

must make use of receptor mediated transport systems or channels across the membrane

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6
Q

generally only what types of molecules cross the membrane?

A

uncharged

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7
Q

define what the pKa is

A
  • pH @ which the drug is 50% dissociated and 50% associated
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8
Q

in its associated form a weak acid is

A

non-ionized

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9
Q

as a weak acid dissociates the acid and hydrogen are

A

ionized

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10
Q

in the associated form a weak base is

A

ionized

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11
Q

as a base drug dissociates the base is

A

non-ionized

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12
Q

what form of the drugs can more readily pass through the phospholipid membrane?

A

the non-ionized (uncharged) form

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13
Q

a decrease in pH means there are ________ ________ for binding

increased acidity

A

more H+ ions

protonated form of the drug predominates

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14
Q

an increase in acidity means there is more weak ________ mobilized across the membrane an less weak ________

A
  • acid
  • base
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15
Q

if the pH is greater than the pKa which form of the drug predominates?

A
  • dissociated or non-protonated form
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16
Q

describe ion trapping for a weak acid drug

A
  • pH rises above the pKa (more basic), more of the drug dissociates trapping the drug in
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17
Q

describe ion trapping for a weak base drug

A
  • pH drops below the pKa (more acidic) more of the drug is in its associated form
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18
Q

The pH of the stomach is approximately 2 which is going to be less than the pKa of most drugs. This would mean that weak acids and weak bases (drugs) are in the protonated or associated form. Which of these two types of drugs will more readily be absorbed from the stomach and which is more likely “trapped” in the stomach?

A

absorbed: weak acid
trapped: weak base

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19
Q

what is the primary location of absorption of orally administered drugs?

A

the small intestine

larger surface area increases amount of drug absorbed

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20
Q

define bioavailability

A

fraction of administered drug that reaches the site of measurement in the body

measured in the peripheral venous blood

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21
Q

describe the 1st pass effect

A

following absorption from the small intestine high drug concentration in the blood passes through the liver where its metabolized. from the liver the blood concentration of the drug (bioavaliability) is decreased

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22
Q

bioavaliability following IV administration is 100%, why?

A

b/c it is administered straight into the blood

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23
Q

other routes (not IV) will haver lower bioavaliability why?

A

b/c the drug will be absorbed by the small intestine and the liver

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24
Q

define distribution

A

delivery and uptake of drugs into tissues in order to reach site of action and exert their biological effect

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25
Q

what are the system related factors that influence distribution?

A
  • blood flow
  • capillary surface
  • capillary permeability
  • cellular uptake systems
  • plasma protein binding
  • organ size/fluid vol.
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26
Q

what are the drug related factors that influence distribution?

A
  • lipid solubility
  • charge
  • polarity
  • MW/ size
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27
Q

higher blood flow = higher

A

capillary surface

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28
Q

which tissues will receive larger drug concentrations?

A

well-perfused tissues

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29
Q

poorly-perfused tissues will recieve the drug at a

A

slower rate

30
Q

if drug permeability is sufficiently high what becomes rate-limiting?

A

blood flow

known as perfussion/ flow-limited drugs

31
Q

describe permeability-limited drugs

A

those whose uptake is slow enough that transport across capillaries/ cell mem. is rate limiting

32
Q

permeability-limited drugs generally have what characteristics?

A
  • polar
  • charged
  • low lipid solubility
33
Q

describe plasma protein binding

A

only free unbound fraction of a drug is capable of binding to receptors to produce the desired effect

34
Q

give an example of a tissue that is leakier to drugs

A

the small intestine

small ions/ polar solutes pass through paracellular pores

34
Q

give examples of tissues that are more tight to drugs

A
  • skin
  • stomach
  • large intestine
  • bv of brain and testes
35
Q

the primary route of drug entry into the CNS is

A

passive diffusion across membranes

36
Q

most of the drugs that cross the BBB are…

BBB: blood brain barrier

A

highly lipid soluble

37
Q

what is a disadvantage to the highly lipid soluble drugs that have to cross the BBB

A

puts a limitation to the avaliable compounds for brain disorder treatments

38
Q

what is a benefit to the highly lipid soluble drugs that have to cross the BBB

A

restricts entry of toxic substances

39
Q

drugs that can cross the BBB can be compromised in which patiens?

A
  • infants
  • elderly
  • brain injuries
  • certain diseases
40
Q

most drugs are metabolized in the liver by

A

microsomal enzymes

41
Q

microsomal enzymes in the liver form ___________ which increases the _________ _________ for excretion.

A
  • metabolites
  • water solubility
42
Q

drugs can be __________ or __________

A

inactive or active

43
Q

what is the term for the inactive form of a drug?

A

prodrug

44
Q

most prodrugs are inactive until they are

A

passed through the liver

45
Q

what are the phases in drug metabolism?

A
  • phase 1: functionalization
  • phase 2: conjugation
46
Q

phase 1 reactions include what type of enzymes? where are they localized?

A
  • oxidative
  • SER
47
Q

phase 1 is aka

A

bioactivation/ inactivation

48
Q

phase 1 reactions make drugs slightly more ________. How?

A

soluble

  • by the addition of polar functional groups

known as functionalization

49
Q

what are the functional groups that are added during phase 1 that make the drugs slightly more soluble?

A

-OH
-COOH
-NH2
-SH
-O

50
Q

phase 2 reactions in drug metabolism include what type of enzymes? these can be integral to the…

A
  • cytosolic
  • SER
51
Q

define conjugation

A

the attachment of highly polar groups to increase polarity making the drug more soluble for elimination

52
Q

what are the highly polar groups that are used to make drugs more soluble?

A
  • glucuronide
  • glutathione
53
Q

what is the primary group of enzyme families that mediate drug metabolism?

A

cytochrome P450 superfamily

54
Q

what are some mechanisms in the regulation of drug metabolism? (specifically enzyme systems)

A

up or downregulating enzyme systems such as cytochrome P450

55
Q

phase 2 reactions are aka

A

bioinactivatioin or conjugation

56
Q

describe the induction of CYP-450 enzyme metabolism

induction=activation

A

factors that increase hepatic metabolizing enzymes increase enzyme metabolism and decrease the active drug concentration in the body therefore decreasing the desired effect

57
Q

describe the inhibition of CYP-450 enzyme metabolism

A

competition between compoundds causes enzyme saturation which
- slows the patent drug metabolism
- raises [plasma]
increasing the effect or toxicity of the drug

58
Q

give an example of ‘inhibition of CYP-450 enzyme metabolism’

A

grapefruit juice competes for cytochrome enzymes leading to an increase [drug]

59
Q

define 1st order kinetics

A

a constant percentage of drug is metabolized over a period of time

60
Q

1st order kinetics is proportional to it concentration therefore it is

A

concentration dependent

61
Q

define 0 order kinetics

A

a constant amount of drug is metabolized over a given period of time

62
Q

zero order kinetics is independent to the drug’s concentration therefore it is

A

concentration independent

63
Q

what is a drug half-life?

A

the time for a drug to lose half of its pharmacological activity

64
Q

elimination is the

A

irrevesible loss of drug from a body

65
Q

what are 2 methods of elimination?

A
  1. metabolism
  2. excretion
66
Q

elimination of a drug through metabolism occurs in which body parts?

A

liver, GI tract, kidney, lung

67
Q

elimination of a drug through metabolism is aka

A

chemical conversion

68
Q

elimination of a drug through excretion occurs in which body parts?

A

kidney, liver, lung, skin

69
Q

elimination of a drug through excretion is aka

A

diffusion, flow, evaporation

70
Q

renal elimination =

A

glomerular filtration + tubular secretion - tubular reabsorption
___________________________
[D] in plasma

71
Q

KD= ____/____ = _____/_____

A

k2/k1

[L][R]/[LR]

Pharmacology (9 decks)

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