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PHRM 501 > Exam 3: Basic of Pharmacokinetics I > Flashcards

Exam 3: Basic of Pharmacokinetics I Flashcards

1
Q

Histamine H2 receptor

A

-Type of receptor: This is a GPCR really only present significantly in the GI tract
• Stomach
• Small intestine

Its endogenous ligand is histamine
Histamine stimulates gastric acid production

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2
Q

Famotidine H2 receptor

A

It is a competitive antagonist for histamine
• It blocks histamine from binding, hence less acid is
produced
• It is used to treat GERD

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3
Q

H2 receptors are

A

transmembrane proteins
•A single peptide with seven membrane spanning regions.
•Ligand binding initiates release of GDP from G-protein subunits from the intracellular side and allows binding instead to GTP
•The result is an increase in activity of adenylyl cyclase.
•Response time: Slow with a duration of seconds to min

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4
Q

GABAa receptor

A

This is a ligand-gated ion channel expressed in the brain•Its endogenous ligand is gamma-aminobutyric acid (GABA)
•GABA is an inhibitory neurotransmitter
•When GABA binds, it allows chloride ions to pass
•This inhibits neurotransmission
•Response time: Rapid with a duration of milliseconds

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5
Q

Zolpidem is what

A

is a GABAa receptor agonist
- It binds allosterically to GABAA and helps GABA bind
•This inhibits neurotransmission above and beyond natural levels
•It is used to treat insomnia

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6
Q

GABAs is a protein with

A

five subunits (a,B, y’s) that are combined to yield a functional receptor

  • It has two binding sites for its endogenous ligand GABA that effect Cl- passage through a central pore
  • It has one allosteric binding site for benzodiazepines
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7
Q

Pharmacokinetics

A

What body does to drug
The relationship between dose and effect ( dose-concentration)

-ADME

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8
Q

Pharmacodynamics

A 
What drug does to the body
Concentration-effect
-Receptor-Drug interactions
- Cell signaling/2nd messenger
-Receptor expression/gene regulation
- Potency and Efficacy
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9
Q

Affinity

A
  • usually expressed as the dissociation constant (Kd)
    • KD=concentration of free drug at which half of the receptors are bound
    • Concentration of free drug (D)
    • Concentration of free receptors (R)
    • Concentration of bound drug-receptors (DR)
    • Expressed in molar units (µM, nM, pM)
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10
Q

A small/low Kd indicates

A

high affinity

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11
Q

Formula for finding Kd

A

Kd = [D][R] / [DR]

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12
Q

As we increase the drug concentration,

A

we increase the amount of receptor binding

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13
Q

More drug-bound receptor equates

A

to greater biological effect

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14
Q

Increase in dose results in

A

increase in plasma conc. which increases the response/effect

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15
Q

EC50

A

The drug conc. at which yields 50% maximal response

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16
Q

If the receptor has lower affinity for a drug

A

it will require more of that drug to bind to the same number of receptors

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17
Q

Potency

A

amount of drug (conc.) needed to produce a certain effect

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18
Q

Efficacy

A

maximal effect a drug produces regardless of dose

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19
Q

ED50

A

dose that is therapeutically effective in 50% of the population

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20
Q

TD50

A

Dose that causes toxic effects in 50% of the population

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21
Q

LD50

A

Dose that is lethal in 50% of the population (animal)

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22
Q

Therapeutic Index

A

Ratio between toxic dose and effective dose

• Therapeutic Index (TI) = TD50/ED50

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23
Q

Is it preferable to have:
A. a high therapeutic index or
B. a low therapeutic index?

A

A. a high therapeutic index

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24
Q

Absorption

A

Dissolution/liberation of drug from formulation
• Gastric emptying
• Passive/facilitated/active transport through intestinal wall

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25
Q

Metabolism

A
  • Intestinal microbiota
  • Enterocyte enzymes
  • First pass effect
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26
Q

Distribution

A
  • Highly perfused tissues - Blood, liver, kidney, heart, lungs
  • Poorly perfused tissues - Fat, muscle, CSF
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27
Q

Excretion

A

Filtration/secretion into urine

• Biliary excretion

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28
Q

Cmax

A

Max observed plasma drug conc.

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29
Q

Tmax

A

Time it takes to reach Cmax

30
Q

MTC

A

Maximum Therapeutic Concentration

31
Q

MEC

A

Minimum Effective Concentration

32
Q

MTC-MEC

A

Therapeutic window/range

33
Q

Latency/ Onset of effect

A

How long it takes to get to Minimum Effective Concentration (MEC)

34
Q

Serum

A

soluble components of blood obtained after clotting and centrifugation

35
Q

Plasma

A

soluble components of blood, clotting factors are inactivated (i.e.-fibrinogen)

36
Q

Buffy coat

A

WBCs and platelets

37
Q

Whole blood

A

Consists of:

  • WBCs
  • RBCs
  • platelets
  • plasma proteins
  • small molecules
  • ions
  • water
38
Q

Concentration is

A

mass / volume

mass of drug = amount of drug (mg)
Volume (Units= L, mL and cc)

39
Q

Blood volume

A

5 L

40
Q

Plasma volume

A

Blood - cells = 2.5 L

41
Q

Hemocrit

A

% of blood volume that cells take up

42
Q

By what route of administration do we assume 100% absorption?

A

IV bolus

43
Q

Soluble substances will partition more into

A

the plasma

44
Q

Insoluble substances will partition/ go into

A

fat

45
Q

Volume of distribution

A

Theoretical volume that the drug homogeneously distributes into
- How large of a volume is needed to account for the observed plasma concentration given
the introduced dose

46
Q

Volume of distribution (Vd) formula

A

Vd = Amount of drug (mg) / [Conc] (mg/L)

Amount of drug absorbed on top
Plasma Conc. (C0, (mg/L))

  • Assumes 100% absorption
47
Q

Intravascular

A

within blood vessels

48
Q

Plasma

A

fluid between RBCs and WBCs in the blood

49
Q

Intracellular fluid

A

fluid within RBCs and WBCs

50
Q

Extravascular

A

outside of blood vessels

51
Q

Interstitial fluid

A

fluid between tissue cells in the extravascular space

52
Q

Intracellular fluid

A

fluid within tissue cells

53
Q

Body Composition

A

Fluids make up 60% of body weight
- Of this ~ 35% is intracellular fluid
Blood volume is 2x of plasma

54
Q

Whole body has how many liters

A

40 L

55
Q

If the drug is highly water soluble, it will be retained where?

A
  • largely in the aqueous media of the body

- will have a higher plasma concentration and a low VD

56
Q

If the drug is highly lipid soluble, it will partition into

A

tissues and fat, hence will have a lower plasma concentration and a high VD

57
Q

A low Vd will have a

A

higher plasma conc.

58
Q

A high Vd will have a

A

Low plasma conc. and will partition into the tissues and fats

59
Q

• If the VD is very small, then the drug is largely present

A

in the intravascular fluid (plasma) only and doesn’t partition much into the intracellular fluids

60
Q

If the VD is 18 L, then the drug is largely present

A

in the total extracellular fluids only and doesn’t

partition much into the intracellular fluids

61
Q

If the VD is ~40 L, then the drug is largely present

A

in all body fluids and not in the tissues

62
Q

Loading dose

A

Drug plasma conc. x Vd

  • dose needed if we have the desired plasma conc. and the Vd
63
Q

Characteristics of drugs in the blood

A

Drug distribute to organs, but it also can distribute to cells within whole blood
- A drug is twice as concentrated in the plasma

64
Q

Drug conc. in the plasma

A

Plasma conc. may not be the same as Blood conc.

Blood: Plasma ratio
Ratio of conc. of drug in whole blood (cells + plasma) versus that in the plasma only

Plasma proteins reside in the plasma – not in the cellular components

65
Q

Chloroquine

A

its an anti-malarial

  • it partitions into and is sequestered by RBCs leaving less drug in the plasma
  • Yields a blood: plasma ratio greater than 1:1
66
Q

Warfarin

A
  • is an anti-coagulant agent
    • Prevents oxidized vitamin K from becoming reduced
    • Prevents formation of clotting proteins
    • Warfarin is highly plasma protein bound
    • It remains sequestered in the plasma
    • This would yield a blood:plasma ratio <1:1
67
Q

Intracellular fluid has what volume

A

24.5L- volume

35%

68
Q

Extracellular fluid

A

18 L-volume

25%

69
Q

Interstitial fluid is what % of body

A

21%-volume

70
Q

Plasma

A

4%

2.5 L- Volume

PHRM 501 (21 decks)

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