Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pharm Block 1 > Drug absorption and distribution > Flashcards

Drug absorption and distribution Flashcards

1
Q

What are the factors affecting drug distribution?

A

a. regional differences in blood flow
b. tissue mass
c. transport mechanisms
d. permeability characteristics
e. ion trapping
f. binding to protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the clinical significance of the area under the curve (AUC)?

A

Bioavailability (F): Used to compare amount (fraction) of drug that reaches the systemic circulation by different routes of administration

Clearance (CL): Used to compare clearance (CL) of a drug in different individuals after administration of the same dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do you calculate AUC?

A

AUC = Dose (i.v.) / CL

AUC = Dose (p.o.) / (CL/F)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do you calculate oral F?

A

F = AUC(po) / AUC(i.v.) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the relationship between AUC and CL in two different patients?

A

Inverse.

CLx/CLy) = (AUCy/AUCx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define drug absorption

A

The processes by which drugs move from their site of administration to the plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Discuss the features of aqueous diffusion

A

small molecules (

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Discuss the features of lipid diffusion

A

passive process driven by concentration gradient

the rate of absorption increases with increasing drug concentration

the more lipid-soluble the faster the rate of transport

lipid-soluble drugs cross membranes readily, but may be poorly soluble in aqueous gut fluids, which may limit their absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is lipid solubility affected by the degree of ionization?

A

non-ionized form is more lipid soluble and thus more readily absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what compounds will be absorbed in the stomach?

A

weak acids, as they will be in their protonated form (non-ionized) and thus more lipid soluble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is unique about the pH of the small intestine?

A

in between the pKa of weak base/weak acid, and thus can absorb the highest percentage of non-ionized acids and bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a general rule of ion trapping?

A

weak acids tend to be concentrated in more alkaline compartments

weak bases tend to be concentrated in more acidic compartments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is the small intestine (rather than the stomach) the main site of absorption of most orally administered drugs?

A

much higher surface area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the first pass effect?

A

some drugs are highly metabolized when they pass through the liver—only a fraction (F) of the absorbed drug reaches the systemic circulation (F = bioavailability).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the enteral route?

A

through the digestive system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the most common enteral route?

A

oral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are some things that can affect the rate of absorption in the enteral route?

A

Stomach contents (food) and gastric emptying time can affect the rates of drug absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can the enterohepatic circulation alter the bioavailability in the enteral route?

A

drugs may be secreted into the bile and reabsorbed via the intestine. This can delay delivery to the systemic circulation and may further reduce bioavailability

19
Q

What is bioavailability?

A

The fraction (F) of the administered dose that reaches the systemic circulation in its active form.

20
Q

How do you calculate Dose(p.o.)?

A

Dose(p.o.) = Dose(i.v.) / F(oral)

21
Q

What is the salt factor (S)?

A

The fraction of total drug that will be delivered as active drug to the systemic circulation

22
Q

How do you calculate loading dose?

A

(Vd x TC) / (F x S)

23
Q

How do you calculate maintenance dose?

A

(CL x TC x T) / (F x S)

24
Q

What are some advantages of buccal/sublingual administration?

A

by-passes portal circulation and therefore avoids first pass metabolism

higher pH may be beneficial for absorption of more basic drugs

25
Q

What are the advantages of rectal administration?

A

~50-60% of absorbed drug by-passes portal circulation and therefore avoids first pass metabolism.

26
Q

What are the benefits of transdermal administration?

A

controlled release of the drug into the patient—enables a steady blood-level profile

user-friendly, convenient, painless, multi-day dosing—improved patient compliance

bypassing the gastrointestinal (GI) tract obviates GI irritation that occurs with some drugs and avoids partial first-pass inactivation by the liver

27
Q

What is parenteral adminstration?

A

not through the digestive system

28
Q

What are the advantages of parenteral administration?

A

greater degree of reliability and precision of administered dose

fewer problems with absorption: not affected by food in the stomach and no “first-pass effect”

29
Q

What are the advantages of subdermal administration?

A

slow, even absorption

may be used as a depot

rate of absorption may be modified by altering blood flow (temperature)

30
Q

What are the advantages of intramuscular administration?

A

more rapid absorption than subcutaneous

rate of absorption may be modified by altering blood flow

31
Q

What are the advantages of i.v. administration?

A

Fastest and most reliable means of achieving a defined blood level, but with a risk of overdose to the bolus effect

32
Q

define ion trapping

A

local pH differences can result in relative concentration of drugs in different compartments

33
Q

how does protein binding influence distribution?

A

plasma proteins can bind a significant fraction of some drugs—only unbound drug distributes to tissues

34
Q

what binds acidic drugs?

A

albumin

35
Q

what binds basic drugs?

A

alpha-1 acid glycoprotein

36
Q

What is one compartment distribution?

A

a rapid equilibrium is achieved between plasma and tissue distribution following drug administration. Plasma concentration-time profile declines mono-exponentially.

37
Q

What is two compartment distribution?

A

rapid distribution to a central compartment (plasma) is followed by slow distribution to other tissues/binding sites (second compartment). This results in a bi-exponential plasma concentration-time profile

the initial distribution follows a multi-exponential phase

the elimination phase is monoexponential

38
Q

Define volume of distribution (Vd)

A

A measure of how evenly distributed a drug is in the body

theoretical volume of fluid into which the total drug administered would have to be diluted to produce the concentration in plasma

39
Q

How do you calculate Vd?

A

Vd = Dose / C0

C0 = initial concentration at time 0

40
Q

What are the major compartments?

A 
—plasma (5% of body weight)
—interstitial fluid (16%)
—intracellular fluid (35%)
—transcellular fluid (2%)
—fat (20%)
41
Q

Where are lipid-insoluble drugs confined to?

A

plasma and interstitial fluids

most do not enter the brain following acute dosing

42
Q

Where do lipid-soluble drugs distribute to?

A

reach all compartments, may accumulate in fat

43
Q

What can act as drug reservoirs, and what are the effects?

A

Fat and Muscle

Gradual release of drug from these sites can prolong the therapeutic effect or result in toxicity.

44
Q

What else in the plasma can act as a drug reservoir, and what will release the drug?

A

Plasma proteins can also serve as a drug reservoir

Sulfonamides may compete for protein binding and increase the unbound fraction of other drug

Pharm Block 1 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions