Modified-release dosage PK MCQs With Answer

Introduction: This quiz collection on Modified-release dosage PK is designed for M.Pharm students studying Advanced Biopharmaceutics & Pharmacokinetics (MPH 202T). It focuses on pharmacokinetic principles and mathematical concepts critical to designing and evaluating sustained-, controlled- and pulsatile-release formulations. Questions cover release mechanisms, kinetics models (zero-order, first-order, Higuchi, Korsmeyer-Peppas), IVIVC levels, flip‑flop kinetics, dosing strategies, steady-state considerations, and formulation-related factors such as multi-unit vs single-unit systems and polymer behavior. Each MCQ aims to reinforce problem-solving and conceptual understanding required for formulation development, regulatory assessment, and clinical translation of modified-release products.

Q1. Which of the following best describes a zero-order drug release from a modified-release dosage form?

• Rate of drug release decreases exponentially with time
• Constant amount of drug is released per unit time
• Release rate is proportional to surface area and concentration gradient
• Drug release occurs only after a lag time and then all at once

Correct Answer: Constant amount of drug is released per unit time

Q2. In a matrix-type sustained release tablet governed by Higuchi kinetics, the cumulative amount of drug released (Q) is proportional to which mathematical function of time?

• Q ∝ t (linear)
• Q ∝ t^2 (quadratic)
• Q ∝ t^0.5 (square root of time)
• Q ∝ e^(-kt) (exponential decay)

Correct Answer: Q ∝ t^0.5 (square root of time)

Q3. Which release mechanism is MOST likely when drug release from a polymeric device shows a Korsmeyer-Peppas release exponent (n) of 0.6 for a cylindrical tablet?

• Pure Fickian diffusion
• Case II transport (relaxational/erosional)
• Anomalous (non-Fickian) transport—combination of diffusion and polymer relaxation
• Zero-order release

Correct Answer: Anomalous (non-Fickian) transport—combination of diffusion and polymer relaxation

Q4. For an oral controlled-release product designed to maintain Css at a target level, which of the following relations correctly gives the required constant input rate R0 (mass/time) under steady-state conditions?

• R0 = Vd × Css × kel
• R0 = Cl × Css
• R0 = (Dose × F) / τ
• R0 = kel / (Vd × Css)

Correct Answer: R0 = Cl × Css

Q5. Flip‑flop kinetics in modified-release formulations occurs when:

• Absorption is much faster than elimination, so elimination controls plasma profile
• Absorption is much slower than elimination, so absorption rate controls terminal slope
• The drug follows zero-order absorption and first-order elimination simultaneously
• There is no absorption phase and drug is directly administered into systemic circulation

Correct Answer: Absorption is much slower than elimination, so absorption rate controls terminal slope

Q6. Which parameter is most directly reduced by using a modified-release formulation compared to an immediate-release form, assuming same total daily dose and bioavailability?

• Area under the plasma concentration–time curve (AUC)
• Mean residence time (MRT)
• Peak-to-trough fluctuation in plasma concentration (peak-trough swing)
• Systemic clearance (Cl)

Correct Answer: Peak-to-trough fluctuation in plasma concentration (peak-trough swing)

Q7. For multiple dosing of an immediate-release drug with first-order elimination, the accumulation ratio R (Css peak over Css after first dose) is given by R = 1/(1 – e^-kelτ). How will increasing dosing interval τ affect R?

• R increases (greater accumulation)
• R decreases (less accumulation)
• R remains unchanged
• R becomes negative

Correct Answer: R decreases (less accumulation)

Q8. Which IVIVC level corresponds to a point-to-point correlation between in vitro dissolution and in vivo plasma concentration profile (i.e., predictive of the entire plasma curve)?

• Level A
• Level B
• Level C
• Level D

Correct Answer: Level A

Q9. A controlled-release tablet releases drug by erosion of the matrix. Which polymer characteristic MOST strongly influences the erosion-controlled release rate?

• Polymer glass transition temperature (Tg) only
• Polymer molecular weight and hydrophilicity
• Drug pKa only
• Tablet color and shape only

Correct Answer: Polymer molecular weight and hydrophilicity

Q10. When designing a once-daily modified-release product, which pharmacokinetic property of the drug favors success of a single-unit sustained-release tablet?

• Very short half-life (<1 hour) and high required daily dose
• Narrow therapeutic index with large interindividual variability
• Small dose, moderate half-life (6–12 h), and good oral bioavailability
• Extensive first-pass metabolism resulting in very low F

Correct Answer: Small dose, moderate half-life (6–12 h), and good oral bioavailability

Q11. For a once-daily modified-release product, to maintain average steady-state concentration (Css,avg) equal to desired target using total daily dose D and dosing interval τ = 24 h, which formula is correct when bioavailability F and clearance Cl are known?

• Css,avg = (F × D) / (Cl × τ)
• Css,avg = (Cl × τ) / (F × D)
• Css,avg = (F × Cl) / (D × τ)
• Css,avg = (D) / (F × Cl × τ)

Correct Answer: Css,avg = (F × D) / (Cl × τ)

Q12. Which statement about multi-unit (e.g., pellets) versus single-unit modified-release systems is TRUE?

• Single-unit systems always have less risk of dose dumping than multi-unit systems
• Multi-unit systems distribute more uniformly in the GI tract and reduce variability from food and GI motility
• Multi-unit systems cannot provide delayed or pulsatile release
• Single-unit systems are preferred when minimizing intersubject variability in gastric emptying is critical

Correct Answer: Multi-unit systems distribute more uniformly in the GI tract and reduce variability from food and GI motility

Q13. A drug with first-order elimination has kel = 0.1 h^-1. For a twice-daily controlled-release product (τ = 12 h), calculate the accumulation factor (Racc) for fluctuation using R = 1/(1 – e^-kelτ). Which is closest?

• R ≈ 1.1
• R ≈ 1.27
• R ≈ 2.5
• R ≈ 10

Correct Answer: R ≈ 1.27

Q14. Which in vivo condition is MOST likely to alter the release profile of an enteric-coated modified-release tablet?

• Rapid small intestinal transit with low gastric residence
• Normal fed-state gastric emptying with low pH meals
• Presence of bile salts in small intestine
• Altered gastric pH due to proton pump inhibitor therapy

Correct Answer: Altered gastric pH due to proton pump inhibitor therapy

Q15. For a reservoir-type controlled-release implant providing near zero-order release, which factor primarily determines the release rate?

• Surface area of the reservoir and permeability of the rate-controlling membrane
• Total drug load only, independent of membrane properties
• Systemic clearance of the drug
• Color and size of the implant

Correct Answer: Surface area of the reservoir and permeability of the rate-controlling membrane

Q16. Which mathematical model is most appropriate to describe dissolution from a planar polymeric film where diffusion through a swollen polymer controls release?

• Higuchi model (Q ∝ t^0.5)
• Michaelis-Menten kinetics
• Langmuir adsorption isotherm
• Zero-order kinetics only

Correct Answer: Higuchi model (Q ∝ t^0.5)

Q17. A modified-release formulation aims to reduce Cmax but maintain AUC equal to immediate release. Which of the following is a correct expectation?

• Cmax will be lower and Tmax will be delayed; AUC remains similar if F unchanged
• Cmax will be higher and AUC will decrease
• Tmax will be unchanged and AUC will increase
• Both Cmax and AUC will decrease due to slowing release

Correct Answer: Cmax will be lower and Tmax will be delayed; AUC remains similar if F unchanged

Q18. In establishing a Level A IVIVC, deconvolution of plasma data is often performed. What is deconvolution used for in this context?

• To convert in vitro dissolution to tablet hardness
• To estimate the in vivo input (absorption) rate from plasma concentration-time data
• To calculate the partition coefficient of the drug
• To determine the melting point of the polymer

Correct Answer: To estimate the in vivo input (absorption) rate from plasma concentration-time data

Q19. Which of the following situations would most likely require a loading dose when switching a patient to a modified-release product designed to release drug slowly over 24 hours?

• Drug has very long half-life and slow release would delay attainment of therapeutic level
• Drug has ultrashort half-life and immediate effect is not needed
• Drug exhibits linear pharmacokinetics with fast onset
• Drug is given topically and not systemically absorbed

Correct Answer: Drug has very long half-life and slow release would delay attainment of therapeutic level

Q20. Which analytical approach is most useful to determine whether a modified-release formulation shows true zero-order release versus apparent zero-order over a limited timeframe?

• Plot cumulative amount released versus square root of time only
• Apply model-fitting to multiple kinetics (zero-order, first-order, Higuchi, Korsmeyer-Peppas) and compare goodness-of-fit metrics
• Measure only dissolution at a single time point
• Assess only tablet hardness and friability

Correct Answer: Apply model-fitting to multiple kinetics (zero-order, first-order, Higuchi, Korsmeyer-Peppas) and compare goodness-of-fit metrics

Download