Exam 2 - Vd & Protein Binding

Question 1

Volume of distribution (Vd)

Answer 1

relates the total amount of drug in the body at any time (M(t)) to the drug concentration in blood/plasma (Cp(t))

Question 2

What 3 things does the Vd reflex?

Answer 2

1. the polarity of the drug
2. its binding to plasma proteins
3. its binding to tissue proteins

Question 3

Total body water (TBW)

Answer 3

the sume of intracellular and extracellular water (typically about 60% of body weight)

Question 4

Benchmark Values: Blood volume

Answer 4

0.07 L/kg

Question 5

Benchmark Values: Tissue volume (aqueous)

Answer 5

0.53 L/kg

Question 6

Benchmark Values: Total body water

Answer 6

0.60 L/kg

Question 7

Benchmark Values: Body volume

Answer 7

1.0 L/kg

Question 8

Benchmark Values: Body mass

Answer 8

70 kg

Question 9

Small Vd example

Answer 9

Heparin (Vd = 0.06 L/kg)

Question 10

Large Vd example

Answer 10

Digoxin (Vd = 7.1 - 8.6 L/kg)

Question 11

Intermediate Vd examples (2)

Answer 11

Phenytoin (Vd = 0.6 - 0.8 L/kg)

Atenolol (Vd = 0.7 L/kg)

Question 12

Small Vd (about 0.06 L/kg)

Answer 12

drug is confined to the vasculature

Question 13

Large Vd (above 4L/kg)

Answer 13

extensive extravascular binding

Question 14

Intermediate Vd (about 1.0 L/kg)

Answer 14

• High plasma protein binding (fub < 0.1): distribution in aqueous and non-aqueous regions
• Low plasma protein binding (fub > 0.9): distribution primarily in total body water

Question 15

Does Vd represent a real physiological volume?

Answer 15

No