Q: Which equation correctly represents the urinary excretion rate of a drug?

$$\text{Urinary Excretion Rate} = \text{Filtration Rate} + \text{Secretion Rate} - \text{Reabsorption Rate}$$

Question 1

Which of the following best describes the difference between drug excretion and drug metabolism?

Accepted Answer

Excretion is the physical removal of unchanged drug from the body, while metabolism is the conversion of the parent drug to a metabolite.

Question 2

A drug is highly bound to plasma proteins. How does this affect its glomerular filtration and excretion?

Accepted Answer

It decreases filtration and excretion because only free drug is filtered at the glomerulus.

Question 3

Which of the following drugs would be most likely to undergo enterohepatic recycling, prolonging its effect?

Accepted Answer

A drug with a molecular weight greater than 300 kD and some polar characteristics.

Question 4

Which equation correctly represents the urinary excretion rate of a drug?

Accepted Answer

$$	ext{Urinary Excretion Rate} = 	ext{Filtration Rate} + 	ext{Secretion Rate} - 	ext{Reabsorption Rate}$$

Question 5

A patient is admitted to the ER with aspirin (a weak acid) toxicity. To promote excretion of aspirin, what should you do to the urine?

Accepted Answer

Alkalinize the urine to increase ionization and trap aspirin in the filtrate.

Question 6

Which of the following statements about tubular secretion is correct?

Accepted Answer

Tubular secretion involves active transport of drugs, and drugs may compete for the same transporters.

Question 7

Which organ is primarily responsible for drug metabolism?

Accepted Answer

Liver

Question 8

Which of the following best explains why ionized drugs are more likely to be excreted in urine?

Accepted Answer

Ionized drugs are water-soluble and cannot be passively reabsorbed, so they are trapped in the filtrate.

Question 9

Which of the following is the correct formula for total body clearance ($$Cl_{total}) if $$renal clearance ($$Cl_R) $$and non-renal clearance ($$Cl_{NR}) $$are known?

Accepted Answer

$$Cl_{total} = Cl_R + Cl_{NR}$$

Question 10

A patient is taking two drugs that are both organic acids and are secreted by the same transporter in the proximal tubule. What is a likely outcome?

Accepted Answer

Competition for the transporter may decrease secretion of one or both drugs, increasing their plasma concentrations.

Question 11

Which of the following best describes the concept of clearance ($$Cl) in $$pharmacokinetics?

Accepted Answer

The volume of blood from which drug is completely removed per unit time.

Question 12

Which process is most affected by the pH of urine when considering the excretion of weak acids and bases?

Accepted Answer

Tubular reabsorption

Question 13

Which of the following is a real-life example of a drug interaction at the level of renal secretion?

Accepted Answer

Probenecid inhibits the transporter for uric acid, affecting the excretion of other drugs like penicillin.

Question 14

Which of the following best explains why clearance is a preferred parameter over rate of elimination in pharmacokinetic equations?

Accepted Answer

Clearance is usually constant for most drugs, while rate of elimination is not.

Question 15

A weak base drug is overdosed. According to the principles of ion trapping, what should be done to the urine to promote its excretion?

Accepted Answer

Acidify the urine to increase ionization and trap the weak base in the filtrate.

Question 16

Which of the following is NOT a major route of drug excretion from the body?

Accepted Answer

Metabolism by the liver

Question 17

Which of the following best describes the effect of protein displacement on drug filtration at the glomerulus?

Accepted Answer

Protein displacement increases the free drug concentration, increasing filtration and excretion.

Drug Elimination and Renal Physiology: Mechanisms, Processes, and Clinical Applications

Study Guide - Practice Questions

Study Guide - Flashcards