Drug Biotechnology Multiple Choice Questions on “Drugs Distribution – Volume”.
1. In equation X=Vd C, what does Vd denotes?
a) Density
b) Volume of blood
c) Volume of body
d) The volume of the body fluid in which the drug is getting dissolved
Answer: d
Clarification: Concentration of drug in plasma C is directly proportional to the amount of drug in body X. The proportionality constant Vd has the unit of volume and is also called the apparent volume of distribution. It is the volume of the body fluid into which a drug is dissolved.
2. The amount of drug in the body is directly proportional to the concentration of the drug in plasma.
a) True
b) False
Answer: a
Clarification: Concentration of drug in plasma C is directly proportional to the amount of drug in body X. The proportionality constant Vd has the unit of volume and is also called the apparent volume of distribution. It is the volume of the body fluid into which a drug is dissolved.
3. The body water has 3 distinct compartments. Which one of these is not one of the compartments?
a) Vascular fluid
b) Intracellular fluid
c) Extracellular fluid
d) Between the tissue layers
Answer: d
Clarification: The body water has 3 distinct compartments. The name of the compartments is vascular fluid/ blood, extracellular fluid (excluding plasma), intracellular fluid (excluding blood cells).
4. How can you determine the extracellular fluid volume?
a) Evans blue
b) Na+
c) D20
d) Tritiated water
Answer: b
Clarification: ECF volume can be determined by substances which can easily penetrate the capillary membrane and distribute to the whole ECF but will not cross the membrane for e.g. Na+, Cl–, Br–, SCN–, SO42-.
5. How a patient’s plasma volume can be determined?
a) Evans blue
b) Na+
c) D20
d) Tritiated water
Answer: a
Clarification: The plasma volume can be determined by the use of high molecular weight dyes or substances which can easily get bind to plasma albumin. E.g. dyes like Evans blue, indocyanine green, I-131 albumin.
6. The total body water volume can be determined by using high molecular weight dyes.
a) True
b) False
Answer: b
Clarification: The plasma volume can be determined by the use of high molecular weight dyes or substances which can easily get bind to plasma albumin. Total body water can be determined by heavy water or tritiated water and lipid soluble substances like antipyrine.
7. How will you determine the intracellular fluid volume?
a) Evans blue
b) Na+
c) Difference between total body water and ECF volume
d) Tritiated water
Answer: c
Clarification: The intracellular fluid volume can be determined by finding out the difference between the TBW and the ECF volume. The intracellular fluid volume is approximately 27 litres.
8. What will be the apparent volume of distribution of warfarin?
a) The apparent volume of distribution is less than the true volume of distribution
b) The apparent volume of distribution is more than the true volume of distribution
c) The apparent volume of distribution is equal to the true volume of distribution
d) Warfarin is not a medicine
Answer: a
Clarification: Drugs which bind to plasma protein or other blood components such as that of warfarin, their apparent volume of distribution is less than the true volume of distribution. The volume of distribution of these drugs lies between blood volume and total body water volume.
9. What will bet the apparent volume of distribution of drugs which binds selectively to extravascular tissues?
a) The apparent volume of distribution is less than the true volume of distribution
b) The apparent volume of distribution is more than the true volume of distribution
c) The apparent volume of distribution is equal to the true volume of distribution
d) The apparent volume of distribution is equal to the volume of extravascular tissues
Answer: b
Clarification: Drugs which binds selectively to extravascular tissues have an apparent volume of distribution is more than the true volume of distribution. The volume of distribution of these drugs is always greater than 42 litres or total body water volume. For example, chloroquine has volume distribution of approximately 15,000 litres.
10. Factors altering the binding of the drug to the blood increases the volume of distribution of the drug and the factors that influence drug binding to the extravascular component decreases the volume of distribution.
a) True
b) False
Answer: a
Clarification: Factors altering the binding of the drug to the blood increases the volume of distribution of the drug and the factors that influence drug binding to the extravascular component decreases the volume of distribution. Other factors that influence the volume of distribution are changes in tissue perfusion, permeability, changes in physicochemical characteristics of the drug.