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Biomedical Lab III > Lab 2 > Flashcards

Lab 2 Flashcards

1
Q

Lipophilicity is also known as _______

A

hydrophobicity

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2
Q

the lipophilicity of a drug greatly affects what?

A

its distribution in biological tissues

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3
Q

the cell membrane consists of…..

A

2 lipid layers intercepted with some hydrophilic pores

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4
Q

What can pass through the hydrophilic pores in the cell membrane?

A

ONLY small water-soluble molecules can permeate through these pores

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5
Q

true or false

the cell membrane is lipophilic

A

true

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6
Q

since the cell membrane is lipophilic, drugs have to be ______ to cross the membrane

A

drugs have to be sufficiently hydrophobic to cross the membrane

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7
Q

most drugs are transferred across the membrane by what process?

A

passive diffusion

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8
Q

the rate of diffusion of drugs through the membrane is dependent on what factors?
(5 of them)

A

-molecular size
-solubility in the surrounding aqueous phase
-concentration of the drug
-permeability
-tissue blood flow

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9
Q

the greater the concentration of the drug at the absorption site, the ______ its absorption

A

GREATER

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10
Q

As mentioned, the greater the concentration of the drug at the absorption site, the greater its absorption.
therefore, the drug must have sufficient…

A

AQUEOUS solubility

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11
Q

true or false

drug permeability decreases with hydrophobicity

A

FALSE – increases

the drug must diffuse through the lipid membrane

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12
Q

for ____ and _____ preparations, the drug must overcome the biological membrane barrier to reach _________

A

for GI and TOPICAL preparations, the drug must overcome the biological membrane barrier to reach BLOOD CIRCULATION

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13
Q

a good drug candidate must have……..

A

both hydrophilic and hydrophobic properties for ABSORPTION AND DISTRIBUTION in the biological tissue

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14
Q

“partition coefficient” is used to express what?

A

the ability of a drug to distribute itself between TWO IMMISCIBLE SOLVENTS (lipid and aqueous solvents)

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15
Q

what is the partition coefficient abbreviated as?

A

Kpc

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16
Q

what is Kpc expressed as?

A

the ratio of the concentration of the drug in the non-polar lipid phase vs the polar aqueous phase

kpc = conc of drug in lipid phase/conc in drug in aqueous phase

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17
Q

the partition coefficient relates to the _____ species of the drug

A

NEUTRAL (non-ionized or zwitterion)

zwitterion: equal positive and negative charges in a molecule

18
Q

when determining the drug partition coefficient, the drug must be……..

A

in the SAME CHEMICAL FORM in BOTH SOLVENTS and not react, ionize, or form dimers and complexes with each other

19
Q

the relative solubility of a substance in ___ and ___ is a measure of its lipophilicity

A

in organic solvent (water-immiscible) and in water

20
Q

what is the most suitable solvent system to test the “in vivo” partitioning ability of a drug?

A

n-octanol and water

21
Q

n-Octanol is a ______ solvent

A

NON POLAR

22
Q

How does n-Octanol better mimic a lipid bilayer membrane?

A

the water content of n-octanol is similar to that of an actual lipid membrane

23
Q

what working with n-octanol, which of its properties must be considered?

A

it has a very high boiling point (198 degrees celsius).

therefore, in lab experiments, other non polar solvents with low boiling points (such as dichloromethane) are used

24
Q

what is the boiling point of DCM (dichloromethane)

A

39-40 degrees celsius

25
Q

explain the properties of DCM (dichloromethane)

A

a colorless, volatile organic solvent NOT miscible in water. has a low boiling point (39-40 degrees celsius)

commonly used in extraction procedures

26
Q

besides boiling point, what other property of the solvents used in measuring partition ability must be considered?

A

the density of the solvents

27
Q

give the order of density of:

DCM (dichloromethane)
water
n-octanol
and ethyl acetate

A

least dense = n-octanol
ethyl acetate
water
most dense = dichloromethane

28
Q

when n-Octanol is used as the non-polar solvent, will water or n-octanol be the bottom layer?

A

WATER LAYER will be on the bottom because it is more dense

29
Q

for the pharmacokinetic processes of absorption, distribution, and excretion, the drug must be able to distribute itself between what 2 places?

A
  1. Between aqueous extracellular fluids (blood, interstitial fluid, urine) and the lipid membrane
  2. Between the lipid membrane and the aqueous cytosol
30
Q

As mentioned, for absorption, distribution, and excretion to occur, the drug must be able to distribute itself between aqueous extracellular fluids and the lipid membrane, as well as between the lipid membrane and aqueous cytosol.

in this sense, the drug goes through ______ between………

A

PARTITIONING between 2 immiscible aqueous and lipid solvents

31
Q

in general, the drug must be sufficiently lipophilic to passively diffuse through the lipid cell membrane, but what else must be considered?

A

the drug cannot be so lipophilic that it cannot diffuse into the cytosol or solubilize in the aqueous cell environment

32
Q

________ is an important factor for predicting a drug’s pharmacological effects, designing dosage forms, and selecting excipients and routes of administration

A

PARTITION COEFFICIENT

33
Q

Partition coefficient is useful to predict the……

A

behavior and fate of drugs in the body

34
Q

true or false

highly polar (hydrophilic) drugs are well absorbed in the GI tract and skin

A

FALSE — poorly absorbed

35
Q

highly hydrophilic drugs are poorly absorbed in the GI tract and skin.
what is the solution to this?

A

they may need to be administered via IV route

36
Q

true or false

lipid drugs (when sufficiently soluble in water) may absorb better in the GI tract than highly hydrophilic drugs

A

TRUE

37
Q

what can be added to topical dosage forms to improve absorption?

A

permeability enhancers

38
Q

during drug development, the drug molecular structure is modified to include what?

A

hydrophobic drugs to improve lipophilcity

39
Q

very hydrophobic drugs have ____ partition coefficient values

A

HIGH

40
Q

Which type of drugs are able to produce CNS effects?
how?

A

very hydrophobic drugs are able to produce CNS effects because they tend to partition favorable across the lipid BBB (blood brain barrier)

41
Q

Dilution factor formula

A

Dilution factor = initial volume + diluent volume/initial volume

(aka final volume/initial volume)

42
Q
A

Biomedical Lab III (10 decks)

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