Drug Absorption #3 Flashcards Preview

Pharmaceutics Spring 2016 > Drug Absorption #3 > Flashcards

Flashcards in Drug Absorption #3 Deck (46)
1

pH partition theory is related to

absorption

2

What is the assumption of the pH partition theory

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

3

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

stomach; intestine

4

_______ form are not absorbed

ionized

5

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

FALSE: WAS NOT

6

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

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

7

Passive diffusion is driven by ______

kinetic energy

8

Which of the following would decrease when a drug is more rapidly absorbed?
a) AUC
b) Efficacy
c) Cmax
d) Potency
e) Tmax

e) Tmax

9

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

-partition coefficient
-lipid solubility
-rate of absorption

10

The absorption rate ______ as the lipid solubility is increasing

increases

11

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

passive diffusion

12

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

carrier mediated or paracellular

13

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

TRUE

14

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

an experiment that depends on
-energy
-inhibits the carrier
-saturation occurs

15

Prodrugs are _______-->_____-

inactive, the body changes the prodrug to its active form

16

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

-poor absorption
-poor solubility
-instability
-poor distribution
-poor taste
-pain on injection

17

Weak Acids have...

a higher absorption at lower pH (more unionized form)

18

Absorption of ____ is very slow

ions

19

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

lipid ; has a higher absorption

20

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

dissolution

21

The AUC for large particles is typically smaller...why?

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

22

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

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

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

FALSE
-generally move by paracellular transport
-polar compounds would not easily cross through lipophilic membrane

24

dissolution

a process; how solid gets turned into a solution

25

Particle size effects _____ and _____

dissolution and absorption

26

_____ is more water soluble

ionized

27

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

higher; lower

28

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

base

29

Why is the salt form of a drug usually administered?

because the salt form is more soluble

30

Salt form vs. Free Form

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

31

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

FALSE: DOES NOT HAVE

32

______ change pH in microenvironment around dissolving particle

excipients

33

polymorphism

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

34

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

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

35

metastable form

if conversion rate is SLOW

36

Which form has the greatest solubility?
Stable or Unstable

Unstable (smaller AUC)

37

Do we always want RAPID dissolution?

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

38

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

dissolution

39

amorphous state (2)

-molecules are arranged in the solid form RANDOMLY
-higher solubility--> higher absorption

40

crystalline state

-molecules are arranged in a more STRUCTURED form

41

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

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

42

solvate

the solvent is trapped within the solid crystal

43

hydrate (2)

-water
-less soluble in water than the anhydrous form

44

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

LOWER

45

_____ form is more soluble in water

anhydrous

46

Ampicillin TriHYDRATE would be ____ solubility than anhydrous form

SLOWER