In-vitro dissolution testing MCQs With Answer

In-vitro dissolution testing MCQs With Answer — Introduction
This collection of multiple-choice questions focuses on in-vitro dissolution testing, a cornerstone of Modern Bio-Analytical Techniques for M.Pharm students. The questions cover fundamental principles (sink conditions, dissolution kinetics), apparatus selection (USP I–IV and other configurations), media selection including biorelevant fluids, method validation (precision, robustness, discriminating power), and advanced topics like IVIVC, dissolution of poorly soluble drugs, and modified-release systems. Each question is crafted to deepen conceptual understanding and practical problem-solving skills required in formulation development, quality control, and regulatory submissions. Use these MCQs to reinforce theory, prepare for exams, and bridge laboratory practice with regulatory expectations.

Q1. Which of the following most accurately defines the term “sink conditions” in dissolution testing?

• The medium volume and composition ensure the drug concentration remains below 10–30% of its saturation solubility
• The medium pH is maintained at physiological value throughout the test
• No precipitation occurs during the dissolution run irrespective of drug concentration
• The dissolution apparatus maintains a constant temperature of 25°C

Correct Answer: The medium volume and composition ensure the drug concentration remains below 10–30% of its saturation solubility

Q2. Which USP dissolution apparatus is most appropriate for testing a buoyant or floating dosage form designed for gastro-retentive delivery?

• USP Apparatus I (Basket)
• USP Apparatus II (Paddle)
• USP Apparatus III (Reciprocating Cylinder)
• USP Apparatus V (Paddle over Disk)

Correct Answer: USP Apparatus III (Reciprocating Cylinder)

Q3. Which kinetic model is commonly used to describe drug release from a matrix tablet when release is controlled by diffusion through a polymer network?

• First-order kinetics
• Higuchi model
• Zero-order kinetics
• Michaelis–Menten model

Correct Answer: Higuchi model

Q4. The discrimination power of a dissolution method refers to:

• Its ability to measure temperature accurately during the test
• The method’s capability to detect meaningful formulation or process changes that affect product performance
• The number of sampling time points used in the test
• The visual clarity of the dissolution medium

Correct Answer: The method’s capability to detect meaningful formulation or process changes that affect product performance

Q5. When developing a dissolution method for a weakly basic drug, which of the following media strategies is most appropriate to simulate gastric-to-intestinal transition?

• Use only phosphate buffer at pH 7.4 for the entire run
• Start in acidic medium (pH ~1.2) then switch to pH 6.8 or pH 6.5 to simulate intestinal conditions
• Use pure organic solvents like methanol to maintain solubility
• Always use media containing surfactants at a single pH

Correct Answer: Start in acidic medium (pH ~1.2) then switch to pH 6.8 or pH 6.5 to simulate intestinal conditions

Q6. Which of the following filters is most suitable for removing undissolved excipients while minimally adsorbing a lipophilic drug during sample withdrawal?

• Glass fiber filter without pre-rinsing
• Polyvinylidene difluoride (PVDF) filter pre-rinsed with dissolution medium containing surfactant
• Cellulose acetate filter always used dry
• No filtration — use direct injection of the whole sample

Correct Answer: Polyvinylidene difluoride (PVDF) filter pre-rinsed with dissolution medium containing surfactant

Q7. The similarity factor f2 used to compare two dissolution profiles will indicate profiles are similar when f2 is:

• Less than 50
• Between 50 and 100
• Greater than 100
• Exactly 0

Correct Answer: Between 50 and 100

Q8. Which in-vitro–in-vivo correlation (IVIVC) level demonstrates a correlation between a single point in-vitro metric and a pharmacokinetic parameter like Cmax?

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

Correct Answer: Level C

Q9. In intrinsic dissolution rate (IDR) studies, which parameter is kept constant to measure the dissolution rate per unit surface area?

• Agitator type only
• Surface area of the compacted drug disk
• Medium temperature at room temperature (25°C)
• Drug particle size distribution in the bulk powder

Correct Answer: Surface area of the compacted drug disk

Q10. For a poorly water-soluble compound, which approach is least appropriate to enhance apparent dissolution in a biorelevant in vitro test?

• Use of surfactants or bile salts in the dissolution medium
• Reducing particle size by micronization or nanonization
• Increasing medium ionic strength to saturate solubility
• Using solid dispersion or lipid-based formulation

Correct Answer: Increasing medium ionic strength to saturate solubility

Q11. During validation of a dissolution method, which attribute specifically examines the effect of small deliberate variations in test conditions like agitation speed, medium volume, or pH?

• Specificity
• Accuracy
• Robustness
• Linearity

Correct Answer: Robustness

Q12. Which USP apparatus is particularly useful to simulate gastrointestinal transit and media changes, and is often used for modified-release dosage forms?

• USP Apparatus II (Paddle)
• USP Apparatus I (Basket)
• USP Apparatus IV (Flow-through cell)
• USP Apparatus V (Paddle over Disk)

Correct Answer: USP Apparatus IV (Flow-through cell)

Q13. In a dissolution profile for a matrix controlled-release tablet, a log cumulative percent remaining vs. time plot yields a straight line. This suggests which order of kinetics?

• Zero-order kinetics
• First-order kinetics
• Higuchi square-root time dependence
• Korsmeyer-Peppas anomalous transport

Correct Answer: First-order kinetics

Q14. Which of the following is a primary reason to include surfactants like sodium lauryl sulfate (SLS) in dissolution media for poorly soluble drugs?

• To sterilize the dissolution medium
• To increase wetting and apparent solubility, improving sink conditions
• To change the drug’s pKa
• To reduce medium viscosity drastically

Correct Answer: To increase wetting and apparent solubility, improving sink conditions

Q15. When performing dissolution testing for coated pellets inside capsules, which sample handling consideration is most critical to obtain representative results?

• Ignoring capsule disintegration time because only pellets matter
• Ensuring capsule shell dissolves or is pierced/removed consistently before pellet release
• Using the largest paddle speed to accelerate pellet release
• Always testing at 37.5°C to drive faster dissolution

Correct Answer: Ensuring capsule shell dissolves or is pierced/removed consistently before pellet release

Q16. A dissolution method that is biorelevant normally attempts to mimic which of the following?

• The manufacturing environment of the drug product
• The in vivo physiological environment such as pH, bile salts, and transit times
• The in-vitro analytical instrument calibration conditions
• The storage conditions of the finished product

Correct Answer: The in vivo physiological environment such as pH, bile salts, and transit times

Q17. Which statement about the use of paddles versus baskets is correct when selecting apparatus for tablets prone to coning or sticking to the paddle?

• Paddles always give faster dissolution for all dosage forms
• Baskets can prevent coning and provide more uniform hydrodynamics for some tablets
• Paddles eliminate the need for sinkers for floating tablets
• Baskets are only used for powders and never for tablets

Correct Answer: Baskets can prevent coning and provide more uniform hydrodynamics for some tablets

Q18. In a dissolution test, sampling error due to removal of aliquots can be minimized by:

• Never replacing the withdrawn volume to speed equilibrium
• Replacing the withdrawn sample volume with fresh medium prewarmed to test temperature
• Withdrawing very large volumes at each time point
• Filtering samples using any filter without validation

Correct Answer: Replacing the withdrawn sample volume with fresh medium prewarmed to test temperature

Q19. Korsmeyer-Peppas model exponent (n) for cylindrical matrices indicates non-Fickian (anomalous) transport when n is approximately:

• 0.1–0.3
• 0.45–0.89
• 1.2–1.5
• Exactly zero

Correct Answer: 0.45–0.89

Q20. Which regulatory expectation is commonly applied to dissolution specifications for immediate-release oral solid dosage forms?

• Demonstration of discriminatory power and batch-to-batch consistency, often using % dissolved at a specified time points and f2 comparisons where applicable
• Only visual inspection of media clarity after dissolution
• Requirement for dissolution to be complete within 5 minutes for all immediate-release products
• Use of a single, non-validated method for all dosage forms regardless of formulation differences

Correct Answer: Demonstration of discriminatory power and batch-to-batch consistency, often using % dissolved at a specified time points and f2 comparisons where applicable

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