# Drug Biotechnology Questions and Answers – Drugs Excretion – Clearance Concept

This set of Drug Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Drugs Excretion – Clearance Concept”.

1. What is total systemic clearance?
a) Sum of clearance from kidney
b) Sum of clearance from kidney and liver
c) Sum of clearance form non-renal clearances
d) Sum of renal and non-renal clearances

Explanation: The sum of individual clearances by all eliminating organs is called total body clearance or total systemic clearance. It is expressed as the sum of renal and non-renal clearance. This term is applied to all organs involved in drug elimination.

2. What is the equation for clearance?
a) Elimination rate / plasma drug concentration
b) Plasma drug concentration/elimination rate
c) 1 / Plasma drug concentration
d) 1 / Elimination rate

Explanation: Clearance is the hypothetical volume of body fluids containing drug from which the drug will be cleared completely in a specific period of time. It is expressed in ml/min. Clearance is expressed through the equation of elimination rate/plasma drug concentration.

3. What will be the elimination rate if the clearance is 130ml/min and drug concentration is 0.8 g/ml?
a) 104g/min
b) 140g/min
c) 130g/min
d) 100g/min

Explanation: Clearance is expressed through the equation of elimination rate/plasma drug concentration. So, for the elimination rate, the equation becomes clearance * plasma drug concentration. Thus the answer becomes 130*0.8= 104 g/min.

4. What will be the renal clearance if the rate of urinary excretion is 625 ml/min and plasma drug concentration is 4.2 ng/ml?
a) 148.80ml2/ng min
b) 150ml2/ng min
c) 152ml2/ng min
d) 140ml2/ng min

Explanation: Renal clearance is defined as the volume of blood which is completely cleared of the unchanged drug by the kidney. It is expressed as the rate of urinary excretion/plasma drug concentration. Thus the answer is 625/4.2 = 148.80 ml2/ng min.

5. How renal clearance ratio is expressed?
a) Renal clearance of creatinine / renal clearance of the drug
b) 1/renal clearance of the drug
c) Renal clearance of drug/ renal clearance of creatinine
d) 1/renal clearance of creatinine

Explanation: It is the clearance ratio of a drug with that of the clearance value compound which gets cleared by glomerular filtration only. Thus, the renal clearance ratio is expressed by clearance of drug/clearance of creatinine.
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6. What will be the renal clearance ratio of a drug whose renal clearance is 40ml/min and the clearance of creatinine is 95ml/min?
a) 0.421
b) 2.38
c) 0.010
d) 0.025

Explanation: Renal clearance ratio is the ratio between renal clearance of the drug and the renal clearance value compound which gets cleared by glomerular filtration only. Thus, the answer is 40/95=0.421.

7. How do you calculate the rate of excretion by kidneys?
a) Rate of filtration – the rate of secretion – Rate of absorption
b) Rate of filtration + rate of secretion – Rate of absorption
c) Rate of filtration + rate of secretion + Rate of absorption
d) Rate of filtration – the rate of secretion + Rate of absorption

Explanation: The rate of excretion through the kidneys is given by Rate of filtration + rate of secretion – Rate of absorption. Absorption is the reabsorption of the drug particles back to the system thus it gets minus from the filtrated amount and secreted amount.

8. What will be the rate of filtration if the rate of secretion is 0.9 ml/ sec, rate of reabsorption is 0.2 ml/sec and the rate of excretion is 2ml/sec for a particular drug?
a) 3ml/sec
b) 0.3ml/sec
c) 1ml/sec
d) 1.3ml/sec

Explanation: The rate of excretion through the kidneys is given by the Rate of filtration + rate of secretion – Rate of absorption. Thus, for the rate of filtration, the equation becomes Rate of excretion – the rate of secretion + rate of absorption.

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