Pharmacokinetics Quiz on Drug Dosage and Dynamics
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Questions and Answers

Which statement about the drug RESAHC and its binding to a target protein is likely to be true?

  • RESAHC fits a two-compartment pharmacokinetic model
  • RESAHC has more than one unique binding site on each molecule of target protein (correct)
  • RESAHC binds poorly to its target protein
  • None of the above

    • What dosage of the drug should CK Mann receive every 6 hours given his creatinine clearance?

  • 250 mg (correct)
  • 180 mg
  • 150 mg
  • 420 mg

    • What is the plasma level of GETAFIX 5 hours after the administration if the initial values of A and B were determined?

  • 3.25 mg/L
  • 2.66 mg/L (correct)
  • 2.52 mg/L
  • 3.84 mg/L

    • Given that PJ's serum drug concentration is higher than expected, which influence is plausible?

    <p>The antibiotic binds less to plasma protein than anticipated</p> Signup and view all the answers

    Calculate the value of k21 from the given pharmacokinetic data for GETAFIX.

    <p>0.7 hr^-1</p> Signup and view all the answers

    What is the elimination half-life of KUMBACT in Mr. Zbigniew?

    <p>1.4 hours</p> Signup and view all the answers

    What is the overall elimination rate constant, k, for GETAFIX given the values derived from pharmacokinetic analysis?

    <p>0.54 hr^-1</p> Signup and view all the answers

    What is the maximum plasma concentration of KUMBACT based on the provided pharmacokinetic model?

    <p>33.5 mg/L</p> Signup and view all the answers

    What value can be calculated for k12 based on the two-compartment pharmacokinetics of GETAFIX?

    <p>0.41 hr^-1</p> Signup and view all the answers

    Which of the following is NOT a method to extend the release of a drug from a solid oral formulation?

    <p>Mulching</p> Signup and view all the answers

    How can JD's creatinine clearance be estimated accurately considering her weight and serum creatinine level?

    <p>By using a standard formula for creatinine clearance</p> Signup and view all the answers

    Given the uremic state of CK Mann, how should the change in elimination rate constant be quantitatively described?

    <p>The elimination rate constant is notably reduced to 60% of the normal rate.</p> Signup and view all the answers

    What does the value of A represent in the pharmacokinetic profile of GETAFIX?

    <p>Initial concentration of drug in the central compartment</p> Signup and view all the answers

    Which pharmacokinetic parameter represents the rate constant for elimination in the case of KUMBACT?

    <p>0.19</p> Signup and view all the answers

    How is the method of residuals utilized in determining pharmacokinetic constants for GETAFIX?

    <p>To separate compartment drug concentrations and obtain values for k and other constants</p> Signup and view all the answers

    Which characteristic is true regarding prodrugs?

    <p>They require metabolic conversion to become active</p> Signup and view all the answers

    What is the absolute bioavailability of the capsule form of FIXIT based on the given AUC values?

    <p>0.91</p> Signup and view all the answers

    How much higher would the average steady-state plasma concentration for KC be compared to young adults if both receive the same maintenance dose?

    <p>12.5</p> Signup and view all the answers

    Will more Drug A be required for a formulation with a 48-hour duration of release than Drug B?

    <p>True</p> Signup and view all the answers

    What loading dose is recommended to achieve a plasma level of 11 ug/mL with the provided parameters?

    <p>70 mg</p> Signup and view all the answers

    Which product will likely reach maximum plasma concentration first after administration?

    <p>Product A will arrive at maximum plasma concentration sooner</p> Signup and view all the answers

    What factor primarily determines the difference in clearance rates between young adults and octogenarians for the maintenance drug?

    <p>Age-related physiological changes</p> Signup and view all the answers

    Which formulation would most likely result in a lower maximum plasma concentration?

    <p>Product B</p> Signup and view all the answers

    Considering the half-lives of Drug A and Drug B, how would their dosing schedules differ for continuous therapy?

    <p>Drug B would need more frequent dosing</p> Signup and view all the answers

    What is the effect of sodium in the composition of liposomes?

    <p>Increases drug delivery efficiency</p> Signup and view all the answers

    What is the role of an antagonist in pharmacology?

    <p>Inhibits the receptor's physiological response</p> Signup and view all the answers

    What effect do suspending agents have on liquid oral formulations?

    <p>They maintain homogeneity of the suspension</p> Signup and view all the answers

    What can be inferred about the drug SWYITDRAG regarding its renal processing?

    <p>It is unlikely to be reabsorbed after filtration</p> Signup and view all the answers

    How does the choice of beverage affect the plasma concentration of SIMVASTATIN?

    <p>Grapefruit juice decreases plasma concentration</p> Signup and view all the answers

    What is true regarding POTENTDRUG based on its therapeutic range and Michaelis constant?

    <p>Saturation pharmacokinetics applies to its metabolism</p> Signup and view all the answers

    Which phase of metabolism do ATP Binding Cassette transporters primarily operate in?

    <p>Phase III</p> Signup and view all the answers

    What does a low fraction unbound in tissues indicate about the drug SUPADRAG?

    <p>It has minimal distribution in tissues</p> Signup and view all the answers

    What happens to the pharmacologic activity of a prodrug during liver disease?

    <p>The activity may decrease.</p> Signup and view all the answers

    Given the same dosing regimen of GUDHART, who is likely to have a higher blood concentration?

    <p>Irma will have a higher concentration.</p> Signup and view all the answers

    Why are antibodies useful as biopharmaceuticals?

    <p>They are highly specific for their targets.</p> Signup and view all the answers

    Calculate the average drug concentration at steady state for Joe Blow. What is the correct concentration?

    <p>77.5 mg/L</p> Signup and view all the answers

    What does the area-under-the-curve (AUC) represent in pharmacokinetics?

    <p>The extent of drug absorption.</p> Signup and view all the answers

    How do you calculate the relative bioavailability of the FIXIT tablet compared to the capsule?

    <p>Using the ratio of AUCs.</p> Signup and view all the answers

    If Drug A has an elimination half-life of 24 hours, and Drug B has a half-life of 2 hours, how would you describe the elimination rates?

    <p>Drug B clears faster than Drug A.</p> Signup and view all the answers

    What implies that bioavailability can be discerned from plasma concentration-time plots?

    <p>The area under the curve correlates with bioavailability.</p> Signup and view all the answers

    Which drug is a better candidate for formulation into an oral modified-release product?

    <p>Drug A</p> Signup and view all the answers

    Which equation best describes drug dissolution in pharmacokinetics?

    <p>Noyes-Whitney</p> Signup and view all the answers

    What is the metabolism rate constant for the xanthine drug with a half-life of 6 hours, volume distribution of 35 L, and renal clearance of 0.36 L/hour?

    <p>10.8/hour</p> Signup and view all the answers

    Which statement regarding orders of pharmacokinetic processes is TRUE?

    <p>Most drugs follow first order kinetics</p> Signup and view all the answers

    Is the Lineweaver-Burk equation suitable to determine the maximum rate of a metabolic reaction?

    <p>False</p> Signup and view all the answers

    Which drug is likely to show the greatest increase in hepatic clearance with a 50% increase in hepatic blood flow?

    <p>Drug A</p> Signup and view all the answers

    What action will double the duration of pharmacologic response after an i.v. bolus dose?

    <p>Doubling the elimination half-life</p> Signup and view all the answers

    How can hysteresis be overcome in pharmacodynamics?

    <p>Using only free drug in a pharmacodynamics compartment</p> Signup and view all the answers

    Study Notes

    Drug Dosage and Pharmacokinetics

    • Creatinine Clearance and Drug Dosage: A patient with deteriorated creatinine clearance (20 mL/minute) requires a dosage adjustment for a drug primarily filtered by glomerular filtration. The elimination rate constant in uremia is 60% of the normal rate. The new dosage should be 180 mg every 6 hours.

    Plasma Drug Levels

    • Two-Compartment Pharmacokinetics: The drug GETAFIX follows first-order, two-compartment pharmacokinetics. This means drug concentration in the plasma follows a specific pattern in two phases.

    • Plasma Level After Administration (5 hours): With given values (A = 7 mg/L, B = 3.25 mg/L, a = 2.12 hr⁻¹, and b = 0.04 hr⁻¹), the plasma level of GETAFIX after 5 hours is 2.66 mg/L. This calculation takes account of the exponential decay of the drug in the plasma.

    • k₂₁ Calculation: The calculation for k₂₁ (the transfer rate from central to peripheral compartments during two-compartment pharmacokinetics) is completed by using the provided values from the pharmacokinetic analysis, then the equation presented. The result is 0.7 hr⁻¹.

    • k₁₂ Calculation: The calculation for k₁₂ (the transfer rate from the central to peripheral compartments) is calculated based on the given parameters and the equation provided. The answer was found to be 1.339 / hr.

    • k Calculation: k calculation was based on the values and equation provided, resulting in a k value of 0.12 hr⁻¹.

    Additional Pharmacokinetic Concepts

    • Scatchard Plot: A Scatchard plot graphically depicts the binding of a drug (RESAHC) to its target.

    • Statements related to drug binding: The plot suggests that RESAHC binds to more than one unique site on the target protein, indicating a complex binding interaction.

    • Antibiotic Prodrug Considerations: A change in plasma concentration of an antibiotic from the expected level (20 mg/L) to 25 mg/L after five half-lives could be attributed to factors like the drug being a prodrug (systematic absorption), reduced plasma protein binding, inactive metabolizing enzymes or using less of the drug.

    • Pharmacokinetics of KUMBACT: The provided equation Cp = 50(e⁻⁰.1⁹t - e⁻¹⁴t) describes the plasma concentration of KUMBACT over time (t) after a 250 mg oral dose. This equation can be used to calculate the maximum plasma concentration. The maximum plasma concentration is calculateded to be 31.6 mg/L.

    • Elimination Half-life of KUMBACT: The elimination half-life of KUMBACT in the patient was found to be 3.647 hours.

    • Drug Release Mechanisms: Several methods extend drug release for oral solid formulations, including erosion, leaching, mulching, and osmosis.

    • Creatinine Clearance: The formula described for the estimation of creatinine clearance is (140-age)×kg/72×serum creatinine.

    • Maximum Drug Elimination (Maynard): The maximum rate of phenytoin elimination from is Ms. Maynard is 587.32 mg/day and to achieve a steady-state plasma concentration of 15mg/L the dosing rate would need to be 504mg/day.

    • Modified Release Mechanisms: Modified-release products can provide extended release of a drug, reducing dosing frequency or targeting drug release at specific sites in the body..

    • Ideal Body Weight : There are different criteria (e.g, body surface area and ideal body weight criteria)

    • Steady State Drug Concentration (Joe Blow): The steady state concentration for Joe Blow after the adminstration of a repeated 8 hourly dose was calculated to be 3.23 mg/L.

    • Relative Bioavailability: The relative bioavailability of the FIXIT capsule compared to the FIXIT tablet is 0.80 in a patient.

    General Considerations

    • Drug Interactions: The interaction between tetracycline and cations or antacids can affect drug absorption.

    • Pharmacokinetic Processes Orders: The overall rate of elimination for many drugs follows first-order kinetics.

    • Pharmacokinetic Models: Compartment models, while useful for describing drug behavior, may not model human physiology accurately, so extrapolating from data from non-humans may not be completely reliable.

    • Drug Binding to Receptors: An antagonist does not activate the receptor, instead binds to a receptor without activating it.

    • Plasma protein binding: Drugs that are highly plasma protein bound will have a limited effect in the kidneys.

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    Kinetics Practice Problems PDF

    Description

    This quiz covers essential topics in pharmacokinetics, including drug dosage calculations, plasma levels, and elimination half-lives. Participants will engage with questions focusing on specific drugs and their behaviors in the body based on pharmacokinetic principles.

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