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Pharmaceutics Spring 2016 > Drug Absorption #3 > Flashcards

Drug Absorption #3 Flashcards

1
Q

pH partition theory is related to

A

absorption

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2
Q

What is the assumption of the pH partition theory

A

the membrane that molecule would have to cross are lipid and because of that the unionized form is more lipid soluble–> leading to it being absorbed

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3
Q

Acidic drugs would be most unionized in the ____, while basic drugs would be better absorbed in the ______

A

stomach; intestine

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4
Q

_______ form are not absorbed

A

ionized

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5
Q

T/F The Surface area of the intestine WAS taken into consideration for the pH partition theory

A

FALSE: WAS NOT

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6
Q

T/F For a drug undergoing passive diffusion, movement of drug across the membrane stops when drug concentration on both sides of the membrane becomes equal

A

FALSE
o Drug movement across the membrane does not stop when the concentration is equal on both sides
o No net gain or loss of drug on either side of the membrane
o The drug is at equilibrium
o Movement in both directions is equal

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7
Q

Passive diffusion is driven by ______

A

kinetic energy

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8
Q

Which of the following would decrease when a drug is more rapidly absorbed?

a) AUC
b) Efficacy
c) Cmax
d) Potency
e) Tmax

A

e) Tmax

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9
Q

The relationship between _____, _____, and _____ are directly related

A
  • partition coefficient
  • lipid solubility
  • rate of absorption
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10
Q

The absorption rate ______ as the lipid solubility is increasing

A

increases

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11
Q

Lipophilic groups have better absorption, what mechanism do they use?

A

passive diffusion

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12
Q

Hydrophilic groups all essentially have the same absorption, what mechanism do they use?

A

carrier mediated or paracellular

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13
Q

T/F There are fewer pores/channels in the ileum compared the jejunum so absorption is lower

A

TRUE

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14
Q

An experiment that would allow us to distinguish between carrier mediated vs. diffusion. (3)

A

an experiment that depends on

  • energy
  • inhibits the carrier
  • saturation occurs
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15
Q

Prodrugs are _______–>_____-

A

inactive, the body changes the prodrug to its active form

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16
Q

What are the reasons as to why prodrugs are developed? (6)

A
  • poor absorption
  • poor solubility
  • instability
  • poor distribution
  • poor taste
  • pain on injection
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17
Q

Weak Acids have…

A

a higher absorption at lower pH (more unionized form)

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18
Q

Absorption of ____ is very slow

A

ions

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19
Q

The addition of an -O functional group makes the drug more _____ soluble–>

A

lipid ; has a higher absorption

20
Q

The rate of ____ can effect the amount of drug that is actually absorbed

A

dissolution

21
Q

The AUC for large particles is typically smaller…why?

A

b/c the drug must first go into solution–> large particles take longer to go into solution

22
Q

T/F A drug administered as an oral solution would be expected to be completely absorbed from the GI tract

A

FALSE

  • Could precipitate in stomach/intestine
  • Decomposition could occur in stomach/intestine
  • First-pass metabolism
  • If transporter required, saturation and/or competition is possible
23
Q

T/ F Polar drugs would primarily be absorbed from the SI by transcellular route

A

FALSE

  • generally move by paracellular transport
  • polar compounds would not easily cross through lipophilic membrane
24
Q

dissolution

A

a process; how solid gets turned into a solution

25
Q

Particle size effects _____ and _____

A

dissolution and absorption

26
Q

_____ is more water soluble

A

ionized

27
Q

more ionized form
Acid dissolve more at _____ pH
Base dissolve more at ____ pH

A

higher; lower

28
Q

Ketoconazole is a weak ______. Which means that it is less soluble at a higher pH

A

base

29
Q

Why is the salt form of a drug usually administered?

A

because the salt form is more soluble

30
Q

Salt form vs. Free Form

A

Faster RATE and EXTENT of absorption in the salt form (shorter Tmax and higher AUC)

31
Q

T/F pH of the environment HAS an effect on the dissolution rate of the salt form

A

FALSE: DOES NOT HAVE

32
Q

______ change pH in microenvironment around dissolving particle

A

excipients

33
Q

polymorphism

A

the ability of a molecule to exist in more than one crystalline state

34
Q

T/F Only one form of the polymorphic state is stable

A

TRUE; overtime the unstable will convert to the stable form (beta form)

35
Q

metastable form

A

if conversion rate is SLOW

36
Q

Which form has the greatest solubility?

Stable or Unstable

A

Unstable (smaller AUC)

37
Q

Do we always want RAPID dissolution?

A

NO. Not for drugs that are extended release, blood pressure or glucose medications

38
Q

What would be the expected rate limiting step in the absorption process for a solid poorly soluble and highly permeable drug?

a) dissolution
b) diffusion
c) blood flow

A

dissolution

39
Q

amorphous state (2)

A
  • molecules are arranged in the solid form RANDOMLY

- higher solubility–> higher absorption

40
Q

crystalline state

A

-molecules are arranged in a more STRUCTURED form

41
Q

The bioavailability of various drug products can be evaluated by comparing their plasma conc.-time curves. The 3 most important parameters of comparison obtained directly from the curves are
A. biologic half life, absorption rate constant, AUC
B. Time of peak concentration (tmax), absorption rate constant, elimination rate constant
C. maximum drug concentration, time of peak concentration (tmax), duration of action
D. AUC, time of peak concentration (tmax), maximum drug concentration
E. rate of elimination, AUC, rate of absorption

A

D. AUC, time of peak concentration (tmax), maximum drug concentration tells us something about RATE and EXTENT of absorption

42
Q

solvate

A

the solvent is trapped within the solid crystal

43
Q

hydrate (2)

A
  • water

- less soluble in water than the anhydrous form

44
Q

Generally, the greater the degree of solvation the _______ the solubility in a medium that is the same as solvate molecules

A

LOWER

45
Q

_____ form is more soluble in water

A

anhydrous

46
Q

Ampicillin TriHYDRATE would be ____ solubility than anhydrous form

A

SLOWER

Pharmaceutics Spring 2016 (20 decks)

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