Pharmacokinetics (ADME principles) Practice Questions

Question 1

What is the primary mechanism for iron absorption in the duodenum?

Accepted Answer

DMT1 transporter

Answer

Simple diffusion

Answer

Passive paracellular transport

Answer

Endocytosis

Question 2

A 65-year-old female patient with a past medical history of diabetes mellitus and an allergy to penicillin develops an infected abscess positive for MRSA on the third day of her hospital stay. She is started on an IV infusion of vancomycin at a dose of 1000 mg every 12 hours. Vancomycin is eliminated by first-order kinetics and has a half life of 6 hours. The volume of distribution of vancomycin is 0.5 L/kg. Assuming no loading dose is given, how long will it take for the drug to reach 94% of its plasma steady state concentration?

Accepted Answer

24 hours

Answer

30 hours

Answer

12 hours

Answer

6 hours

Answer

18 hours

Question 3

A scientist is studying the excretion of a novel toxin X by the kidney in order to understand the dynamics of this new substance. He discovers that this new toxin X has a clearance that is half that of inulin in a particular patient. This patient's filtration fraction is 20% and his para-aminohippuric acid (PAH) dynamics are as follows:

Urine volume: 100 mL/min
Urine PAH concentration: 30 mg/mL
Plasma PAH concentration: 5 mg/mL

Given these findings, what is the clearance of the novel toxin X?

Accepted Answer

60 mL/min

Answer

1,500 mL/min

Answer

600 mL/min

Answer

300 mL/min

Answer

120 mL/min

Question 4

A research group wants to assess the safety and toxicity profile of a new drug. A clinical trial is conducted with 20 volunteers to estimate the maximum tolerated dose and monitor the apparent toxicity of the drug. The study design is best described as which of the following phases of a clinical trial?

Accepted Answer

Phase I

Answer

Phase 0

Answer

Phase III

Answer

Phase V

Answer

Phase II

Question 5

A 26-year-old man comes to the emergency department because of a 1-week history of worsening fatigue, nausea, and vomiting. Six weeks ago, he was diagnosed with latent tuberculosis and appropriate low-dose pharmacotherapy was initiated. Physical examination shows right upper quadrant tenderness and scleral icterus. Laboratory studies show elevated aminotransferases. Impaired function of which of the following pharmacokinetic processes is the most likely explanation for this patient's symptoms?

Accepted Answer

Acetylation

Answer

Glucuronidation

Answer

Hydrolysis

Answer

Sulfation

Answer

Reduction

Question 6

In a healthy patient with no renal abnormalities, several mechanisms are responsible for moving various filtered substances into and out of the tubules. Para-aminohippurate (PAH) is frequently used to estimate renal blood flow when maintained at low plasma concentrations. The following table illustrates the effect of changing plasma PAH concentrations on PAH excretion:

Plasma PAH concentration (mg/dL)    |    Urinary PAH concentration (mg/dL)
                0                   |                    0
               10                   |                   60
               20                   |                  120
               30                   |                  150
               40                   |                  180

Which of the following mechanisms best explains the decreased rate of increase in PAH excretion observed when plasma PAH concentration exceeds 20 mg/dL?

Accepted Answer

Saturation of PAH transport carriers

Answer

Decreased glomerular filtration of PAH

Answer

Increased rate of PAH reabsorption

Answer

Increased flow rate of tubular contents

Answer

Increased diffusion rate of PAH

Question 7

A researcher is investigating the effects of a new antihypertensive medication on renal physiology. She gives a subject a dose of the new medication, and she then collects plasma and urine samples. She finds the following: Hematocrit: 40%; Serum creatinine: 0.0125 mg/mL; Urine creatinine: 1.25 mg/mL. Urinary output is 1 mL/min. Renal blood flow is 1 L/min. Based on the above information and approximating that the creatinine clearance is equal to the GFR, what answer best approximates filtration fraction in this case?

Accepted Answer

17%

Answer

10%

Answer

33%

Answer

50%

Answer

25%

Question 8

A researcher is investigating the behavior of two novel chemotherapeutic drugs that he believes will be effective against certain forms of lymphoma. In order to evaluate the safety of these drugs, this researcher measures the concentration and rate of elimination of each drug over time. A partial set of the results is provided below.

Time 1:
Concentration of Drug A: 4 mg/dl
Concentration of Drug B: 3 mg/dl
Elimination of Drug A: 1 mg/minute
Elimination of Drug B: 4 mg/minute

Time 2:
Concentration of Drug A: 2 mg/dl
Concentration of Drug B: 15 mg/dl
Elimination of Drug A: 0.5 mg/minute
Elimination of Drug B: 4 mg/minute

Which of the following statements correctly identifies the most likely relationship between the half-life of these two drugs?

Accepted Answer

The half-life of drug A is constant but that of drug B is variable

Answer

The half-life of drug A is always longer than that of drug B

Answer

The half-life of both drug A and drug B are constant

Answer

The half-life of both drug A and drug B are variable

Answer

The half-life of drug A is variable but that of drug B is constant

Question 9

A 65-year-old man with a history of myocardial infarction is admitted to the hospital for treatment of atrial fibrillation with rapid ventricular response. He is 180 cm (5 ft 11 in) tall and weighs 80 kg (173 lb). He is given an intravenous bolus of 150 mg of amiodarone. After 20 minutes, the amiodarone plasma concentration is 2.5 mcg/mL. Amiodarone distributes in the body within minutes, and its elimination half-life after intravenous administration is 30 days. Which of the following values is closest to the volume of distribution of the administered drug?

Accepted Answer

60 L

Answer

80 L

Answer

150 L

Answer

17 L

Answer

10 L

Question 10

An experimental infusable drug, X729, is currently being studied to determine its pharmacokinetics. The drug was found to have a half life of 1.5 hours and is eliminated by first order kinetics. What is the minimum number of hours required to reach a steady state concentration of >90%?

Accepted Answer

6

Answer

3

Answer

7.5

Answer

1.5

Answer

4.5

Pharmacokinetics (ADME principles)

Study Resources

Lessons

Questions

Flashcards

Lessons

Absorption factors and bioavailability

Drug distribution and protein binding

Volume of distribution concepts

Phase I metabolism (oxidation, reduction, hydrolysis)

Phase II metabolism (conjugation reactions)

Cytochrome P450 system

First-pass metabolism

Renal excretion mechanisms

Biliary excretion

Half-life and steady state concepts

Area under the curve calculations

Dosing in renal impairment

Dosing in hepatic impairment

Practice Questions

Flashcards

About Pharmacokinetics (ADME principles) for USMLE

Lessons in Pharmacokinetics (ADME principles)

Master Pharmacokinetics (ADME principles)