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Flashcards in 4. Pharmacokinetics Deck (44):
1

A dose of 750 mg of acetaminophen is administered to a patient. A blood sample is drawn one hour after the dose is administered. The concentration of acetaminophen is measured as 8 mcg/mL (which is 8 mg/L). Acetaminophen has a volume of distribution of 51 L. Determine the total amount of drug remaining in the body 1 hour after dose administration. Do not enter the units, only the number. Round to the nearest whole number.

408

1

A chemist wishes to increase the rate of gut dissolution of a new tablet formulation. Which of the following would be the most useful option to consider for most medications?

A. Decreasing the surface area of the tablet.
B. Increasing the surface area of the tablet.
C. Adding an emulsifying agent.
D. Instructing the patient to take thirty minutes after the morning dose of a proton pump inhibitor.
E. Instructing the patient to take thirty minutes after the morning dose of an antacid.
 

B. In order to increase tablet dissolution the chemist could increase the tablet's surface area and/or decrease the size.

1

A drug that exhibits first-order kinetics will display the following properties:

A. A linear relationship between dose and serum level
B. A nonlinear relationship between dose and serum level
C. A Michaelis-Menten relationship
D. As the concentration increases the AUC decreases in a corresponding manner
E. Short half-life and increased bioavailability
 

A. In first-order kinetics, the rate of elimination is directly proportional to the amount of drug remaining in the body.

2

A medical resident asks the pharmacy student to explain to the medical students why most drugs are weak acids or weak bases. Which of the following points are correct and could be included in the explanation?

A. If the drug dissolves in the gut fluid it will not get absorbed.
B. If the compound is charged it cannot interact with the cell receptors.
C. Weak acids are highly charged compounds in physiological pH.
D. Weak bases are highly charged compounds in physiological pH.
E. Charged compounds dissolve more easily in water than uncharged compounds.
 

E. In order for absorption to occur the drug has to dissolve in the watery-contents of the stomach. If the drug is a weak acid it will have a negative charge and if it is a weak base more of the drug will be charged because more of the drug will have either lost or gained a proton. Charged compounds dissolve easily in water. A dissolved drug can get absorbed into the blood.

2

A drug that exhibits Michaelis-Menten kinetics will display the following properties: (Select ALL that apply.)

A. A linear relationship between dose and serum level until the metabolizing enzymes are saturated
B. Improved distribution
C. A nonlinear relationship between dose and serum level
D. Saturable kinetics
E. Poor bioavailability

A, C, D. Michaelis-Menten, or saturable kinetics, begins as first-order, but when the metabolism becomes saturated, the concentration increases rapidly. Drugs with this type of kinetics begin as first-order kinetics, but can change to zero order once a certain dose is reached and metabolizing enzymes are saturated. At this point, toxicity can result.

3

A new antibiotic for community-acquired pneumonia (CAP) was recently FDA-approved.  The drug was presented at the Pharmacy and Therapeutics Committee meeting.  The drug monograph included the following information:
Community-acquired pneumonia dosing (IV): 675 mg IV Q8H
Community-acquired pneumonia dosing (PO): 675 mg PO TID
Protein binding: 18%
Metabolism: partially hepatic
Half-life (elimination): 1.6 - 2.1 hours 
What is the bioavailability of this new drug?

A. 0%
B. 1%
C. 25%
D. 50%
E. 100%
 

E.

4

A newly approved drug has a volume of distribution of 82 L and a clearance of 9.26 L/hr. Calculate the half-life of this drug. Do not enter the units, only the number. Round to the nearest tenth.

6.1

4

A new antibiotic for community-acquired pneumonia (CAP) was recently FDA-approved. The drug was presented at the Pharmacy and Therapeutics Committee meeting. The drug monograph included the following information: Community-acquired pneumonia dosing (IV): 675 mg IV Q8H Community-acquired pneumonia dosing (PO): 675 mg PO TID Protein binding: 18% Metabolism: partially hepatic Half-life (elimination): 1.6 - 2.1 hours What hospital policy/protocol should this drug be added to?

A. The CAP Policy

B. The Antibiogram Protocol

C. The Therapeutic Interchange Protocol

D. The Pharmacokinetic Policy

E. The High Risk Medication Protocol

C. Drugs like this are easily converted to the oral formulation in the same dose. Most hospitals have a "Therapeutic Interchange" Protocol or "IV to PO" Protocol (approved by the Medical Staff) that allows medications to be converted if certain criteria are met.

5

A patient has overdosed on phenytoin and is experiencing symptoms of phenytoin toxicity. The prescriber asks how much drug the patient has consumed because he wishes to calculate how long it will take the patient to clear the drug. The pharmacist offers the following correct advice: (Select ALL that apply.)

A. Phenytoin exhibits Michaelis-Menten elimination.
B. Once the metabolizing enzymes are saturated, phenytoin elimination follows zero-order elimination. The elimination will not correlate in a linear fashion with the amount of drug consumed.
C. With significant overdose the patient will display extreme irritability, anxiety and difficulty sleeping and concentrating.
D. With significant overdose the patient will exhibit CNS depressant effects.
E. Phenytoin initially follows first-order elimination.

A, B, D, E. When a drug such as phenytoin is overdosed, the elimination changes from first to zero-order. This is because the enzymes that metabolize phenytoin are full of the drug (or saturated) and cannot metabolize the extra drug. The additional phenytoin will not be subjected to first-pass (it will pass through the saturated liver) and increase the serum concentration dramatically. This is called Michaelis-Menten, or saturable, kinetics. Overdose will produce CNS-depressant effects.

5

A patient has been using phenytoin 100 mg three times daily for 6 months. A steady state phenytoin level was taken and found to be 9.8 mcg/mL.  She recently had a seizure, so the prescriber increased the dose to 100 mg with breakfast and lunch, and 200 mg with dinner.  The prescriber calculated that if 300 mg/day provided a level of 9.8 mcg/mL, then 400 mg/day would increase the level to approximately 13 mcg/mL.  After the dosage change, the patient started to slur her words, felt fatigued and returned to the medical office office. The level was retaken and found to be 18.7 mcg/mL. At both visits, her serum albumin level was 4.2 g/dL.  What is the most likely reason for the phenytoin level?

A. Phenytoin exhibits increased metabolism with higher doses.
B. Phenytoin exhibits Michaelis-Menten kinetics.
C. Phenytoin has reduced protein binding at higher doses.
D. Patient non-compliance.
E. The patient did not take with food.

B. The prescriber did not consider that the drug exhibits Michaelis-Menten kinetics. It is important for pharmacists to be prepared to answer questions about Michaelis-Menten kinetics and patient scenarios.

5

A patient is being treated with an investigational drug.  The investigational drug protocol states that the patient should receive one dose of the drug IV, then no further doses should be given until the level reaches 8.5 mg/L or below.  The medication administration record and pertinent information are included below.  In an effort to reduce expense, drawing drug levels should be kept to a minimum during the study period.    
Investigational Drug Dose #1 administered at 0800 on 1/10/15
Dose infused from 0800 to 1000
Serum level: 1/10/15 @ 4pm = 47.9 mg/L 
Serum level: 1/11/15 @ 5pm = 29.7 mg/L
It is currently 5pm on 1/11/15.  How many hours will it take for the patient's serum level to reach exactly 8.5 mg/L so he can receive the next dose of the investigational drug?  Round to the nearest whole number.

A. 24 hours
B. 36 hours
C. 65 hours
D. 72 hours
E. 110 hours

65

 First calculate the patient-specific ke using the two levels and time between the levels with the formula on page 92: ke = [-ln (29.7 / 47.9)] / 25]. Next, use the same formula and the ke to solve for time to reach 8.5 mg/L (you must rearrange the formula): time between levels (or time to reach 8.5 mg/L exactly) = [-ln (8.5 / 29.7) / ke from the previous calculation] = 65 hours.

7

An intravenous drug is administered as a 225 mg dose. The resulting AUC is 52 mg x hr/mL. Bioavailability of the oral formulation is 100%. Calculate the clearance of this drug. Do not enter the units, only the number. Round to the nearest hundredth.

4.33 Bioavailability can be presented as a percentage or a decimal. Cl = 225/52 x 1.0 = 4.33 mL/hr.

9

An oral drug is administered as a 225 mg dose. The resulting AUC is 52 mg x hr/mL. Bioavailability of the oral formulation is 50%. Calculate the clearance of this drug. Do not enter the units, only the number. Round to the nearest two decimal places.

2.16 Bioavailability can be presented as a percentage or a decimal. Cl = 225/52 x 0.5 = 2.16 mL/hr.

11

AUC values of drug X following IV administration of 50 mg and oral administration of 100 mg were found to be 70 mg x hr/mL and 90 mg x hr/mL respectively. Calculate the absolute bioavailability of drug X. Round to the nearest whole number. Do not enter the percent sign.

64

11

Based on knowledge of functional groups, which drug is amphetamine?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these

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A. Drug A in Image Group #6 is amphetamine. It contains an amine functional group.

12

Based on knowledge of functional groups, which drug is an aminoglycoside?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these
 

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C. Drug C in Image Group #3 is gentamicin, an aminoglycoside. Based on the name, it would be expected to have amine groups on the structure. The functional group containing nitrogen in structure D is an amide, not an amine.

13

Based on knowledge of functional groups, which drug is aspirin?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these

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B. Drug B in Image Group #2 is acetylsalicylic acid (aspirin). It is the only drug in this grouping that contains an acidic functional group.

14

Based on knowledge of functional groups, which drug is sulfamethoxazole?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these

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C. Drug C in Image Group #1 is sulfamethoxazole. It is the only drug in this grouping that contains a sulfonamide functional group.

15

Before a drug can be absorbed through the GI tract the following must have taken place to the compound:

A. The drug must be conjugated to a free base.
B. If the drug is an acid it must be encapsulated in a micelle.
C. The drug must be dissoved in the gut solution.
D. The drug must be conjugated to a free acid.
E. The drug must be metabolized to a hydrophilic form.

C. Before an orally administered drug is absorbed it must be dissolved.

17

Choose the correct statements that describe the elimination half-life (t½): (Select ALL that apply.)

A. The half-life is the time required for the plasma concentration of the drug to decrease by 50%.

B. If a drug is eliminated via zero order kinetics, the half life is always the same.

C. The elimination half-life refers to the time it takes for half of dose to be absorbed through the gut lining.

D. After approximately 5 half-lives, the elimination is considered to be nearly complete.

E. The half-life can be calculated if you know the elimination rate constant, ke.

A, D, E.

17

Choose the pharmacokinetic term used to describe how the drug moves from the site of administration and into the circulation:

A. Excretion
B. Dissolution
C. Absorption
D. Distribution
E. Metabolism

C. Absorption is determined by the drug's bioavailability, which is called F, or the F value.

18

Choose the pharmacokinetic term used to describe the dispersion, or passage of the drug throughout the body:

A. Dissolution
B. Absorption
C. Distribution
D. Metabolism
E. Excretion

C. Lipophilic compounds are uncharged, and can pass more easily through lipid membranes. Polar, charged compounds cannot pass easily through cell walls. More of the drug will stay in the blood compartment (such as aminoglycosides, which have a charged amino group).

18

Choose the pharmacokinetic term used to describe oral formulations breaking up in the gut in order for absorption to take place:

A. Dissolution
B. Absorption
C. Distribution
D. Metabolism
E. Excretion
 

A.

19

Choose the pharmacokinetic term used to describe the process by which the body breaks down drugs into compounds that can be more readily eliminated:

A. Dissolution
B. Absorption
C. Distribution
D. Metabolism
E. Excretion

D. The liver (along with drug-metabolizing enzymes in the gut wall) can extract, or pull out, a portion of the drug by changing the drug's structure. This results in less drug being available for therapeutic benefit (or more drug if a pro-drug is hepatically metabolized to the active form.)

21

Choose the pharmacokinetic term used to describe the process by which the body rids itself of drugs or metabolites either through the kidneys or back into the gut:

A. Dissolution
B. Absorption
C. Distribution
D. Metabolism
E. Excretion

E. The primary routes of excretion for most drugs include the kidney (renal excretion) and the gut/liver (via metabolism).

22

Data was obtained after oral and intravenous administration of drug X in volunteers of average weight 50 kg. Following an intravenous dose of 1.2 mg/kg, administered as a bolus injection, the AUC was 4.50 mg x hr/mL. Following a 4.0 mg/kg oral dose, administered as a solution, the AUC was 8.2 mg x hr/mL. Calculate the absolute bioavailability of drug X. Round to the nearest whole number. Do not enter the percent sign.

55

24

Data was obtained after oral and intravenous administration of drug X in volunteers of average weight 50 kg. Following an intravenous dose of 1.2 mg/kg, administered as a bolus injection, the AUC was 4.5 mg x hr/mL. Following a 4 mg/kg oral dose, administered as a capsule, the AUC was 7.36 mg x hr/mL. Calculate the absolute bioavailability of drug X. Round to the nearest whole number. Do not enter the percent sign.

49

25

Doxycycline has a clearance of 4.5 L/hr and a volume of distribution of 65 L. Calculate the half-life of doxycycline. Round to the nearest whole number. Do not enter the units, only the number.

10

25

Following a 225 mcg (0.225 mg) intravenous dose of fentanyl, plasma levels of fentanyl were measured. The extrapolated concentration at time = 0 was 0.286 mcg/L. Calculate the volume of distribution for fentanyl. Do not enter the units, only the number. Round to the nearest whole number.

787

27

Following a 400 mg dose of cefpodoxime, the terminal elimination rate constant was determined to be 0.38 hr-1. Calculate the half-life of cefpodoxime. Round to the nearest whole number. Do not enter the units, only the number.

2

28

Following a 400 mg dose of voriconazole IV the area under the curve is measured at 38 mg x hr/mL. Calculate the apparent clearance. Round to the nearest liter. Do not enter the units, only the number.

11

30

How many half-lives are required to reach steady state (assuming a one compartment model and no loading dose)?

A. Approximately 2
B. Approximately 5
C. Approximately 8
D. Approximately 12
E. Steady state is reached after 2 days of continuous drug administration with no missed doses.

B.

31

Large changes in drug distribution can be caused by small changes in:

A. Release of parathyroid hormone
B. Release of growth hormone
C. Protein binding
D. Protein consumption
E. Protein absorption

C. Changes in albumin (normal range 3.5-5 g/dL) will cause changes in the amount of bound drug, if it is highly protein bound.

33

MK is a 83 y/o female who has been receiving vancomycin for 1 week for a documented MRSA pneumonia. She is 5'1" and weighs 110 pounds.  Her admission SCr was 1 mg/dL.  The pharmacist was called by a nurse, because MK's SCr is now 1.5 mg/dL.  Several vancomycin levels have been drawn.  The following information is available:
Vancomycin regimen: 750 mg IV Q24H at 2100 (stable regimen since 1/1/15) 
Last vancomycin dose:  1/7/15 @ 2100
Vancomycin random level: 1/8/15 @ 1000 = 28 mg/L 
Vancomycin random level: 1/8/15 @ 1300 = 24.7 mg/L
Calculate the vancomycin elimination rate constant. Do not enter the units, only the number. Include the leading zero, if the answer is less than 1. Round to three decimal places.
 

0.042

Use the formula on page 92 for ke. The t is the time between the two levels (1000 to 1300 = 3 hours). ke = [-ln (24.7 / 28)] / 3.

34

MK is a 83 y/o female who has been receiving vancomycin for 1 week for a documented MRSA pneumonia. She is 5'1" and weighs 110 pounds.  Her admission SCr was 1 mg/dL.  The pharmacist was called by a nurse, because MK's SCr is now 1.5 mg/dL.  Several vancomycin levels have been drawn.  The following information is available:
Vancomycin regimen: 750 mg IV Q24H at 2100 (stable regimen since 1/1/15) 
Last vancomycin dose:  1/7/15 @ 2100
Vancomycin random level: 1/8/15 @ 1000 = 28 mg/L 
Vancomycin random level: 1/8/15 @ 1300 = 24.7 mg/L
Calculate MK's vancomycin half-life. Do not enter the units, only the number. Round to the nearest whole number.  

17

Use the formula on page 92 to solve for ke first. ke = [-ln (24.7 / 28)] / 3. Next, use this value to solve for half-life.

36

Phenothiazines contain a thioether functional group. Which drug is a phenothiazine?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these
 

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A.

37

The Noyes-Whitney equation includes this important factor in determining the rate at which a compound will dissolve in the gut:

A. The compound's surface area.
B. The compound's chemical ingredients.
C. The flavoring agent used in the preparation.
D. The coloring used in the preparation.
E. None of the above.

A. Increasing the surface area will speed dissolution. Processes such as micronization can increase surface area dramatically and are used to increase absorption in some drugs which would otherwise be poorly absorbed, including some hormones and some of the fenofibrate formulations.

38

What is the primary pathway of drug degradation in the gut?

A. Oxidation
B. Phase II conjugation reactions
C. Hydrolysis
D. Proteolysis
E. P-glycoprotein efflux drug transportation

C. Hydrolysis (lysis with water) occurs when the compound is cleaved into two parts by the addition of a water molecule. One part of the compound takes the proton (H+) and the other takes the hydroxyl group (OH-).

39

When a drug is administered intravenously, which of the following steps does not occur?

A. Absorption
B. Distribution
C. Metabolism
D. Excretion
E. All of the steps (absorption, distribution, metabolism and excretion) occur when a drug is administered intravenously.

A. When a drug is given IV, there is no absorption. The drug directly enters the systemic circulation.

40

Which drug contains a carboxyl (carboxylic acid) functional group?

A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these

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B. Drug B in Image Group #7 is ibuprofen. It contains a carboxyl functional group.

41

Which drug contains a ketone functional group?


A. Drug A
B. Drug B
C. Drug C
D. Drug D
E. None of these
 

Q image thumb

D. Drug D in Image Group #5 is fenofibrate. It contains a ketone functional group.

42

Which formula is used to describe the rate of drug dissolution (or the rate at which the drug dissolves)?

A. Michaelis-Menten
B. Noyes-Whitney
C. Henderson-Hasselbach
D. Remington's Coefficient
E. Stimmel's
 

B. The rate of dissolution is described by the Noyes-Whitney equation.

43

Which of the following defines pharmacodynamics?

A. What the kidney does to the drug.
B. What the liver does to the drug.
C. What the body does to the drug.
D. What the drug does to the body.
E. What the drug does to the microorganism.
 

D.

44

Which of the following defines pharmacokinetics?

A. What the kidney does to the drug.
B. What the drug does to the body.
C. What the body does to the drug.
D. What the liver does to the drug
E. What the drug does to the microorganism.
 

C.

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