Drug Biotechnology Questions and Answers – Drugs Excretion – Factors Affecting Renal Clearance

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This set of Drug Biotechnology Objective Questions & Answers focuses on “Drugs Excretion – Factors Affecting Renal Clearance”.

1. Which of the following is not a factor of renal excretion?
a) Blood flow to the kidneys
b) Urine pH
c) Blood pH
d) Disease state
View Answer

Answer: c
Explanation: The factors that affect the urinary excretion are, physicochemical properties of the drug, plasma concentration of the drug, Distribution and binding characteristics of the drug, urine pH, and blood flow to the kidneys, disease state, drug interactions, and other biological factors. The blood pH don’t directly affect the renal clearance.
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2. Which of the following is not a physicochemical factor of drug that can affect the renal excretion?
a) Molecular size
b) Disintegration rate
c) pKa of the drug
d) Lipid solubility
View Answer

Answer: b
Explanation: Important physicochemical factor that has effect on the renal excretion are molecular size, pKa of the drug, and lipid solubility. A small molecular sized compound can easily get filtered out by the glomerulus. Compounds of eight below 300 Dalton and water soluble, can get readily excreted by glomerulus. Disintegration rate does not affect the excretion, it will affect absorption.

3. Drugs of molecular range 300-500 Dalton will be excreted out by glomerulus.
a) True
b) False
View Answer

Answer: b
Explanation: Compounds with molecular weight below 300 Dalton will be filtered easily through the glomerulus. Drugs in the molecular weight range of 300-500 Dalton will be filtered through the bile and urine both. Molecules of size more than 500 Dalton will be filtered out through urine but to a lesser extent.
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4. In a graph of rate of excretion versus plasma drug concentration, which kind of drug will give the below shown curve?
drug-biotechnology-objective-questions-answers-q4
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: a
Explanation: Glomerular filtration and reabsorption from the further tubules are directly affected by plasma drug concentration. A drug that will not be bound to the plasma proteins and excreted by only filtration will have linear relationship between the rate of excretion and plasma drug concentration. The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs.

5. In a graph of rate of excretion versus plasma drug concentration, which kind of drug will give the below shown curve?
drug-biotechnology-questions-answers-factors-affecting-renal-clearance-q5
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: c
Explanation: The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs. Drugs that are actively secreted, the rate of excretion increases with increase in plasma concentration up to a saturation level. A drug that will not be bound to the plasma proteins and excreted by only filtration will have linear relationship between the rate of excretion and plasma drug concentration.
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6. In a graph of rate of excretion versus plasma drug concentration, which kind of drug will give the below shown curve? (x axis- rate of excretion, y axis – plasma drug concentration)
drug-biotechnology-questions-answers-factors-affecting-renal-clearance-q6
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: b
Explanation: The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs. Drugs which are actively reabsorbed, excretion is negligible at low plasma concentration. These agents are excreted in urine when their glomerular filtrate concentration exceeds the active reabsorption capacity e.g. glucose.

7. In a graph of renal clearance versus plasma drug concentration, which kind of drug will give the below shown curve?
drug-biotechnology-questions-answers-factors-affecting-renal-clearance-q7
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: a
Explanation: Glomerular filtration and reabsorption from the further tubules are directly affected by plasma drug concentration. A drug that will not be bound to the plasma proteins and excreted by only filtration will have linear relationship between the rate of excretion and plasma drug concentration.
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8. In a graph of renal clearance versus plasma drug concentration, which kind of drug will give the below shown curve?
drug-biotechnology-questions-answers-factors-affecting-renal-clearance-q8
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: c
Explanation: The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs. Drugs that are actively secreted, the rate of excretion increases with an increase in plasma concentration up to a saturation level. The renal clearance will tend to decrease when the plasma concentration is at lower level.

9. In a graph of renal clearance versus plasma drug concentration, which kind of drug will give the below shown curve?
drug-biotechnology-questions-answers-factors-affecting-renal-clearance-q9
a) Drug excreted only by filtration
b) Drug filtered and actively reabsorbed
c) Drug filtered as well as actively secreted
d) Drug reabsorbed actively
View Answer

Answer: b
Explanation: The drugs which are secreted or reabsorbed, the rate increases with an increase in plasma concentration to a point where saturation occurs. Drugs which are actively reabsorbed, excretion is negligible at low plasma concentration. These agents are excreted in urine when their glomerular filtrate concentration exceeds the active reabsorption capacity e.g. glucose.
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10. Clearance is inversely related to volume of distribution.
a) True
b) False
View Answer

Answer: a
Explanation: The clearance decreases when a drug has a large volume of distribution. A drug with large Vd is poorly excreted in urine. Blood restricted to blood compartments have higher excretion rates.

11. Which drugs cannot be filtered through glomerulus?
a) Drugs bound to plasma proteins
b) Unbound
c) Free drug
d) Below molecular weight of 300 Dalton
View Answer

Answer: a
Explanation: Drugs that are bound to plasma behave as macromolecules don’t get filtered through the glomerulus. Unbound free drug which are less than 300 Dalton get filtered by the glomerulus.

12. Which one is the correct equation to calculate the fraction of unbound drug in plasma?
a) Concentration of unbound drug in plasma / total plasma concentration of drug
b) Total plasma concentration of drug / Concentration of unbound drug in plasma
c) 1/Concentration of unbound drug in plasma
d) 1/total plasma concentration of drug
View Answer

Answer: a
Explanation: The fraction of drug bound to plasma proteins can be calculated by the equation fu = Cu/C. Here fu is fraction of unbound drug and Cu is the concentration of unbound drug in plasma and C is the total plasma concentration of the drug.

13. What will be the fraction of unbound drug if the unbound drug concentration is 0.99 g/ml and total plasma concentration is 160 g/ml?
a) 0.006
b) 1.61
c) 0.618
d) 0.010
View Answer

Answer: c
Explanation: The fraction of drug bound to plasma proteins can be calculated by the equation fu = Cu/C. Here fu is fraction of unbound drug and Cu is the concentration of unbound drug in plasma and C is the total plasma concentration of the drug. Therefore 99/160=0.618.

14. What will be the unbound drug concentration if the unbound drug fraction is 0.52 and the total plasma concentration is 140 g/ml?
a) 80 g/ml
b) 82.8 g/ml
c) 70 g/ml
d) 72.8 g/ml
View Answer

Answer: d
Explanation: The fraction of drug bound to plasma proteins can be calculated by the equation fu = Cu/C. Here Fu is fraction of unbound drug and Cu is the concentration of unbound drug in plasma and C is the total plasma concentration of the drug. For the calculation of unbound drug concentration, the equation will be unbound drug fraction * total plasma concentration. Thus the answer will be 0.52*140 = 72.8 g/ml.

15. Age, sex, species, differences in genetic makeup alter drug excretion.
a) True
b) False
View Answer

Answer: a
Explanation: Age, sex, species and strain difference, differences in the genetic make-up, circadian rhythm, etc. alter drug excretion. Renal excretion is 10% lower in females than in males. The renal function of new-borns is 30 to 40% less than adults and attains maturity between 2.5 to 5 months of age.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter