Pharmacokinetics and Drug Dosage Calculations

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Questions and Answers

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

It remains unchanged.

It will increase.

It will decrease. (correct)

It will stabilize.

If twins Amy and Irma both miss doses of the drug GUDHART, how does their blood concentration compare assuming similar pharmacokinetic properties?

Amy will have higher blood concentration than Irma.

Irma will have higher blood concentration than Amy. (correct)

Blood concentrations will be unaffected by missed doses.

Both will have the same blood concentrations.

What is the primary reason antibodies are useful as biopharmaceuticals?

They have low molecular weights.

They are hydrophilic.

They are highly specific. (correct)

They are easily synthesized.

Based on a multiple dose regimen of 150 mg every 6 hours for Joe Blow, what is the average drug concentration at steady state?

135.5 mg/L Signup and view all the answers

What does the area-under-the-curve (AUC) from plasma concentration-time plots primarily indicate?

The extent of absorption. Signup and view all the answers

What is the relative bioavailability of the FIXIT tablet with respect to the capsule based on their AUC values?

1.08 Signup and view all the answers

How does the half-life of Drug A compare to Drug B?

Drug A is eliminated slower than Drug B. Signup and view all the answers

If GUDHART absorption, distribution, and elimination are similar for both women, what result is expected after a missed dose?

Irma will have a higher concentration than Amy. Signup and view all the answers

Which order of kinetics is characterized by the drug amount decreasing proportionally to the amount remaining?

First order Signup and view all the answers

If drug A has a higher intrinsic clearance than drug B, what effect does increasing hepatic blood flow have on both?

Drug A is likely to show a greater increase in clearance. Signup and view all the answers

Which equation is best suited to determine the maximum rate of a reaction involving a substrate and its metabolizing enzyme?

Michaelis-Menten equation Signup and view all the answers

What is the main benefit of doubling the elimination half-life of a drug following an intravenous bolus dose?

Increases the duration of pharmacologic response Signup and view all the answers

More Drug B is needed for release over a 6-hour period than over a 16-hour period.

False Signup and view all the answers

Which statement is accurate regarding the Lineweaver-Burk equation?

It is not suitable for determining the maximum rate of metabolic reactions. Signup and view all the answers

The inclusion of polyethylene glycol in liposomes does which of the following?

Enables them to evade phagocytes Signup and view all the answers

What does an antagonist do in pharmacology?

Binds to a receptor without activating it Signup and view all the answers

What factor would directly double the duration of pharmacologic response after an intravenous bolus dose?

Doubling the elimination half-life Signup and view all the answers

Which of the following equations best describes the drug dissolution process?

Noyes-Whitney equation Signup and view all the answers

Which statement about suspending agents in liquid oral formulations is TRUE?

They retard absorption Signup and view all the answers

Which condition is true for hysteresis in pharmacodynamics?

Occurs with only free drug in pharmacodynamics compartment. Signup and view all the answers

When Kate Johnson takes her dose of SIMVASTATIN with grapefruit juice, what will be the impact on her plasma concentration?

It will be lower than that taken with water Signup and view all the answers

What can be concluded about the drug SWYITDRAG with a molecular weight of 480, being highly plasma protein-bound?

It cannot be filtered in the glomerulus Signup and view all the answers

In which phase of metabolism are ATP Binding Cassette transporters primarily involved?

Phase III Signup and view all the answers

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

It has a low apparent volume of distribution Signup and view all the answers

Which statement is most likely true regarding RESAHC's binding to its target protein?

RESAHC has more than one unique binding site on each molecule of target protein Signup and view all the answers

What plausible factor could explain the higher-than-expected serum drug concentration of the antibiotic in patient PJ?

The antibiotic binds less to plasma protein than anticipated Signup and view all the answers

Using the given pharmacokinetic equation, what is the maximum plasma concentration of KUMBACT?

33.5 mg/L Signup and view all the answers

What is the elimination half-life of KUMBACT in Mr. Zbigniew based on the provided equation?

1.4 hours Signup and view all the answers

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

Mulching Signup and view all the answers

Estimate JD's creatinine clearance based on her clinical parameters.

102 mL/minute Signup and view all the answers

What pharmacokinetic factor is primarily influenced by the information about Ms. Claire Maynard's phenytoin treatment?

Steady-state concentration Signup and view all the answers

Based on the pharmacokinetics, how would the changing metabolic state of a patient influence drug excretion?

Prolonged drug half-life Signup and view all the answers

Determine the maximum rate of phenytoin elimination from Ms. Maynard given an average plasma concentration of 10 mg/L with a Michaelis constant of 4 mg/L.

604.8 mg/day Signup and view all the answers

What dosing rate is necessary for Ms. Claire Maynard to achieve a steady-state plasma concentration of 15 mg/L given her current rate results in a sub-therapeutic level?

504 mg/day Signup and view all the answers

Calculate JD's ideal body weight based on her weight of 105 kg and height of 5 ft 6 inches.

63.8 kg Signup and view all the answers

What dose of SETANDRAG, given every 8 hours, will achieve a steady-state level of 3 mg/mL in an 80 kg individual, considering the volume of distribution is 33.5% of body weight?

186 mg Signup and view all the answers

Are lozenges exempt from USP disintegration specifications?

True Signup and view all the answers

What effect does the interaction between tetracycline and foods containing polyvalent cations have on tetracycline absorption?

Decreased tetracycline absorption Signup and view all the answers

What is a characteristic that modified-release products do NOT possess?

Allow for elimination of drug on a delayed basis directly Signup and view all the answers

Is it true that Michaelis-Menten pharmacokinetics is the only source of non-linearity in drug absorption?

False Signup and view all the answers

Calculate the absolute bioavailability of the capsule form of FIXIT if the AUC after oral tablet is 800 mg.hr/L and the AUC after oral capsule is 640 mg.hr/L.

0.91 Signup and view all the answers

Based on total clearance values, how much higher would the average steady-state plasma concentration in an octogenarian be compared to a young adult if the maintenance dose is 5 mg daily?

6 Signup and view all the answers

Determine if more Drug A would be needed for a formulation with a 48-hour duration of release than Drug B.

True Signup and view all the answers

If an anesthesiologist wants to reach a plasma level of 11 ug/mL using a loading IV dose and a continuous infusion of 1.5 mg/h, what loading dose is recommended for the anesthetic with a half-life of 7 hours and a volume of distribution of 20 L?

70 mg Signup and view all the answers

After administering a single dose of products A and B, which statement is likely true regarding their maximum plasma concentrations?

Product B will arrive at maximum plasma concentration later Signup and view all the answers

What is the primary reason for the difference in pharmacokinetics between Drug A and Drug B based on their elimination half-lives?

Drug B is rapidly eliminated from the body Signup and view all the answers

If a drug's volume of distribution is 30 L and the desired plasma concentration is 5 ug/mL, what loading dose should be calculated assuming first-order kinetics?

200 mg Signup and view all the answers

What impact does the use of a disintegrating agent have on the pharmacokinetics of an oral drug formulation?

Increases drug absorption rate Signup and view all the answers

Study Notes

Drug Dosage and Pharmacokinetics

Creatinine Clearance and Dose Adjustments: Creatinine clearance deterioration to 20 mL/minute necessitates a dose adjustment for a drug primarily eliminated by glomerular filtration. A 60% reduction in elimination rate constant (k_U/k_N) in uremia results in a calculated adjusted dose of 180mg every 6 hours.

Drug Pharmacokinetic Parameters Calculations

Plasma Drug Level after IV Bolus: Given an IV bolus dose of 900 mg GETAFIX, with parameters A = 7 mg/L, B = 3.25 mg/L, a = 2.12 h^-1, and b = 0.04 h^-1, the plasma level after 5 hours can be calculated using the two-compartment model equation to be 2.66 mg/L.
k₂₁ Calculation: The calculation for k₂₁ using the given parameters (A, B, a, and b) is : (7 mg/L * 0.04 h^-1) + (3.25 mg/L * 2.12 h^-1) / (7 mg/L + 3.25 mg/L)≈ ~0.7 hr^-1
k Calculation: The calculation for k using the given parameters (A, B, a, and b) is: ((2.12 h^-1) * (0.04 h^-1)) * (7 mg/L + 3.25 mg/L))/(7 mg/L *0.04h^-1) + (3.25 mg/L * 2.12h^-1) ≈ 0.12 hr^-1
k₁₂ Calculation: The calculation for k₁₂ using the given parameters (A, B, a, and b) is: ((7 mg/L * 3.25 mg/L) * (0.04 h^-1- 2.12 h^-1))² / ((7 mg/L + 3.25 mg/L) * ((7 mg/L * 0.04 h^-1) + (3.25 mg/L* 2.12 h^-1))) ≈ ~0.1 hr^-1

Drug binding and interactions

Scatchard Plot Interpretation: A Scatchard plot reveals information on the drug binding to its target, specifically if the drug has multiple binding sites (indicated by non-linearity on the graph).
Antibiotic Pharmacokinetics: Factors like altered plasma protein binding or metabolic enzyme activity can significantly affect antibiotic drug concentrations if they deviate from expected values.
KUMBACT Pharmacokinetics: The equation defining KUMBACT's plasma concentration, Cp = 50(e^-0.19t - e^-1.4t), allows for calculating maximum plasma concentration (Cp_max) upon substitution of optimal t values to obtain a maximum concentration of 31.6 mg/L.
Elimination Half-life of KUMBACT: The elimination half-life is ~3.65 hours for KUMBACT.

General Pharmacokinetic Considerations

Drug Formulation and Release: Methods like erosion, leaching, and mulching can be employed to control the release of a drug from a solid oral formulation.
Creatinine Clearance Estimation: Estimating creatinine clearance (CrCl) using the Cockcroft-Gault formula or other predictive models is essential to adjusting maintenance doses of drugs to prevent overdose in patients.
Phenytoin Steady State Elimination: The maximum elimination rate for phenytoin can be calculated given the Michaelis-Menten equation and parameters like Michaelis constant (Km), fraction of dose absorbed(F), and steady state concentration (C_ss).
Bioavailability Calculation: Determining the relative bioavailability of a drug from different formulations (e.g., oral tablets versus capsules) using the AUC data.
Pharmacokinetic Interactions: Interactions like those between drugs and polyvalent cations (e.g., in antacids) can alter drug absorption rate or extent, decreasing the absorption of tetracycline in this case.

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Description

Test your understanding of drug dosing and pharmacokinetic parameters in this quiz. Topics include creatinine clearance adjustments, plasma drug levels after IV bolus, and calculations such as k21 and elimination rates. Perfect for pharmacology students and healthcare professionals.