Lecture 2

Question 1

Understanding Volume of Distribution (Vd)

_________ indicates the extent of drug distribution into body fluids.

It does not specify the exact tissue or fluid where the drug is found

Answer 1

Vd

Question 2

____________: Suggests the drug distributes extensively throughout the body.

Answer 2

Large Vd

Question 3

___________: Implies that the drug’s distribution into tissues is
limited.

Answer 3

Small Vd

Question 4

Variability in Distribution
Two drugs might share the same Vd value, but their distribution patterns can differ. For instance, one drug might predominantly distribute into muscles, while another concentrates in adipose tissue.

Question 5

Volume of Distribution(Vd)

Although Vd values sometimes correspond to real physiological volumes, many observed Vd values are clearly not equivalent to real physical volumes

When Vd is much greater than the subject physical volume, this implies sequestration of drug via binding to tissue proteins or concentration in fat

Question 6

Significance of apparent volume of distribution

Typical Vd Values: Most drugs possess a Vd that’s __________ or ___________ to body mass.

Answer 6

less than or equal

Question 7

Impact of Drug Binding:Binding to peripheral tissues or plasma proteins significantly influences Vd(apparent volume of distribution).

Question 8

High Plasma Protein Binding: Leads to a higher initial concentration (Co) and, consequently, a ______ Vd.

Answer 8

smaller

Question 9

High Peripheral Tissue Binding: Results in a lower initial concentration (Co) and a _________ Vd in turn.

Answer 9

larger

Question 10

Vd Beyond Body Mass:
Some drugs might exhibit a Vd that exceeds body mass by multiple times.

Question 11

Distribution Patterns:
Drugs with a substantial apparent Vd tend to be more concentrated in _____________ and less so within the vascular region

Answer 11

extravascular tissues

Question 12

Significance of apparent volume of distribution

Dosing Regimens
Vd is a crucial parameter when establishing correct dosing regimens

Question 13

Significance of apparent volume of distribution

Vd offers insights into the relative quantities of a drug in both vascular and extravascular tissues.

Question 14

Significance of apparent volume of distribution

Physiological Significance:
While Vd doesn’t correspond directly to a specific physiological meaning, it’s essential in determining dosage requirements.

Question 15

Significance of apparent volume of distribution

Dose Proportionality:
Typically, dosing corresponds to Vd. A larger Vd suggests that a _____________ is needed to attain the desired concentration.

Answer 15

more substantial dose

Question 16

Significance of apparent volume of distribution

Foundation Knowledge:
To truly grasp drug distribution, one must first understand the basics of body fluids and tissues.

Question 17

Intracellular water–> 27 Liters

Plasma–>3 Liters

Interstitial water–>12 Liters

Extracellular water–> 15 Liters

Total Body Weight= 40 Liters

Question 18

Total body water of infants = 75 – 85 % of body weight

Total body water of adults = 60 – 55 % of body weight

Question 19

For the body fluid compartments below, rank them from the lowest volume to the highest, in a
typical 70-kg person.

A. Plasma < ECF <ICF < total body water
B. ECF < ICF <plasma < total body water
C. ICF < ECF <plasma <total body water
D. Total body water < plasma < ICF < ECF

Question 20

Volume of Distribution Interpretation

A drug has a Vd = 15-18 L, what that implies?

Its distribution is limited to __________ in a 70 kg

Answer 20

ECF

Question 21

A drug has a Vd = 40 L, what that implies?

Drug distributing into ______________

Answer 21

all body water

Question 22

If a drug has a Vd greater than 40-50 L, what
that implies?

Drug probably is being concentrated in tissues outside the plasma and interstitial fluid or there is ________________

Answer 22

protein/tissue binding

Question 23

Drugs with no extensive distribution into extravascular tissues: well described by 1 compt model EX:
_____________

Answer 23

aminoglycosides

Question 24

Extent of distribution is determined by ____________ of the drug

Answer 24

chemistry

Question 25

Drugs extensively distributed in tissues (e.g., Benzodiazepines, very ___________) or with extensive intracellular uptake may be better described by more complex models

Answer 25

lipophilic