Introduction: In-vitro drug dissolution models MCQs With Answer provide B.Pharm students a focused way to master dissolution testing principles, USP apparatus selection, dissolution media, and release kinetics. This concise guide emphasizes key concepts such as sink conditions, biorelevant media, discriminatory power, IVIVC, similarity factor (f2), and common kinetic models (zero-order, first-order, Higuchi, Korsmeyer-Peppas). Questions explore apparatus I–IV, sampling and filtration, effect of formulation factors (particle size, polymorphism, coating), and methods to optimize poorly soluble drugs. Designed for exam preparation and quality-control practice, these MCQs reinforce regulatory standards, method development, and troubleshooting in dissolution studies. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which USP apparatus is commonly called the paddle apparatus?
- USP Apparatus I (basket)
- USP Apparatus II (paddle)
- USP Apparatus III (reciprocating cylinder)
- USP Apparatus IV (flow-through)
Correct Answer: USP Apparatus II (paddle)
Q2. What is the primary purpose of in-vitro dissolution testing in pharmaceutical development?
- To determine drug toxicity in humans
- To assess drug release rate from a dosage form
- To measure blood plasma concentrations directly
- To evaluate microbial contamination in formulations
Correct Answer: To assess drug release rate from a dosage form
Q3. Which condition best describes “sink conditions” for dissolution testing?
- Drug concentration in medium equals saturation solubility
- Volume of medium is large enough so dissolved drug concentration stays well below saturation
- Medium pH is fixed at pH 7.4 only
- Temperature is below the melting point of the drug
Correct Answer: Volume of medium is large enough so dissolved drug concentration stays well below saturation
Q4. The similarity factor f2 is used to:
- Estimate drug toxicity
- Compare two dissolution profiles for similarity
- Determine melting point of drug substance
- Measure particle size distribution
Correct Answer: Compare two dissolution profiles for similarity
Q5. Which kinetic model assumes a constant amount of drug released per unit time?
- First-order kinetics
- Zero-order kinetics
- Higuchi model
- Korsmeyer-Peppas model
Correct Answer: Zero-order kinetics
Q6. In the Higuchi model, drug release is primarily governed by:
- Surface erosion only
- Partitioning into blood
- Diffusion from a homogeneous matrix
- Immediate dissolution of an entire dose
Correct Answer: Diffusion from a homogeneous matrix
Q7. Which USP apparatus is most suitable for testing transdermal patches and some modified-release forms using constant flow?
- USP Apparatus I (basket)
- USP Apparatus II (paddle)
- USP Apparatus III (reciprocating cylinder)
- USP Apparatus IV (flow-through cell)
Correct Answer: USP Apparatus IV (flow-through cell)
Q8. Which parameter is critical when filtering dissolution samples prior to analysis?
- Filter pore size and adsorption of drug to filter
- Filter color only
- Filter brand name only
- Filter thickness in micrometers without regard to pore size
Correct Answer: Filter pore size and adsorption of drug to filter
Q9. A discriminatory dissolution method primarily aims to:
- Show that all batches are identical regardless of formulation changes
- Detect meaningful formulation or process changes affecting release
- Reduce the need for QC testing
- Maximize dissolution medium volume automatically
Correct Answer: Detect meaningful formulation or process changes affecting release
Q10. Which factor would most likely DECREASE dissolution rate of a poorly soluble drug?
- Reducing particle size
- Increasing surface area
- Using a surfactant in the medium
- Increasing crystalline content (lower solubility polymorph)
Correct Answer: Increasing crystalline content (lower solubility polymorph)
Q11. What is the role of biorelevant media in dissolution testing?
- To provide extreme non-physiological conditions only
- To better mimic gastrointestinal fluids and improve IVIVC
- To sterilize the dosage form during test
- To quickly dissolve all dosage forms regardless of formulation
Correct Answer: To better mimic gastrointestinal fluids and improve IVIVC
Q12. Which dissolution apparatus is described as a reciprocating cylinder?
- USP Apparatus I
- USP Apparatus II
- USP Apparatus III
- USP Apparatus IV
Correct Answer: USP Apparatus III
Q13. In method development, why is paddle speed selection important?
- It affects hydrodynamics, boundary layer thickness, and observed release rate
- It changes chemical structure of drug
- It only affects color of the dissolution medium
- It determines tablet hardness directly
Correct Answer: It affects hydrodynamics, boundary layer thickness, and observed release rate
Q14. The dose number (Do) in dissolution is defined as:
- Ratio of drug dose to the saturation solubility times volume of dissolution medium
- Ratio of tablet weight to capsule weight
- Ratio of dissolution time to sampling interval
- Number of doses in a bottle
Correct Answer: Ratio of drug dose to the saturation solubility times volume of dissolution medium
Q15. Which kinetic model uses the exponent ‘n’ to indicate mechanism of drug release from polymeric systems?
- Zero-order model
- First-order model
- Korsmeyer-Peppas model
- Higuchi model
Correct Answer: Korsmeyer-Peppas model
Q16. What is a typical acceptance criterion using f2 for two dissolution profiles to be considered similar?
- f2 greater than 50
- f2 equal to 10
- f2 less than 20
- f2 equal to zero
Correct Answer: f2 greater than 50
Q17. Which change in formulation would most likely INCREASE dissolution rate?
- Increasing drug crystallinity
- Coating tablets with an insoluble polymer
- Reducing particle size (micronization)
- Removing disintegrant
Correct Answer: Reducing particle size (micronization)
Q18. In quality control, USP <711> refers to:
- Dissolution procedures for solid dosage forms
- Sterility testing of injectables
- Assay of raw materials only
- Particle sizing by laser diffraction
Correct Answer: Dissolution procedures for solid dosage forms
Q19. Which medium additive is commonly used to increase solubility of poorly soluble drugs in dissolution testing?
- Surfactants such as sodium lauryl sulfate
- Preservatives like methylparaben
- Buffers that lower solubility always
- Heavy metals
Correct Answer: Surfactants such as sodium lauryl sulfate
Q20. For immediate-release tablets, which sampling schedule is most appropriate for profile comparison?
- Single time point only
- Multiple time points covering early and late phases (e.g., 5, 15, 30, 45, 60 minutes)
- Sampling every 24 hours
- No sampling is required
Correct Answer: Multiple time points covering early and late phases (e.g., 5, 15, 30, 45, 60 minutes)
Q21. What effect does increasing agitation speed generally have on dissolution?
- Decreases dissolution by stabilizing undissolved particles
- Increases dissolution by reducing boundary layer thickness
- No effect at all
- Causes immediate precipitation of drug
Correct Answer: Increases dissolution by reducing boundary layer thickness
Q22. How does particle size reduction enhance dissolution rate according to Noyes-Whitney equation?
- By decreasing surface area available for dissolution
- By increasing surface area and hence dissolution rate
- By changing drug pKa only
- By converting drug into a gas
Correct Answer: By increasing surface area and hence dissolution rate
Q23. Which of the following is a limitation of in-vitro dissolution tests?
- They can always exactly predict in-vivo absorption
- They may not capture complex physiological variables affecting bioavailability
- They replace the need for any bioequivalence study
- They measure microbial risk only
Correct Answer: They may not capture complex physiological variables affecting bioavailability
Q24. What is the purpose of performing dissolution method robustness testing?
- To evaluate the method’s sensitivity to small deliberate changes in parameters
- To make the method more complex intentionally
- To avoid validation altogether
- To increase tablet hardness artificially
Correct Answer: To evaluate the method’s sensitivity to small deliberate changes in parameters
Q25. Which dissolution test parameter would you adjust if tablet coning occurs at the bottom of the vessel?
- Change paddle speed or use a sinker to prevent coning
- Always reduce medium temperature to 0°C
- Remove the tablet coating during the test
- Add more drug to the tablet
Correct Answer: Change paddle speed or use a sinker to prevent coning
Q26. IVIVC (in-vitro–in-vivo correlation) is most useful for:
- Predicting in-vivo drug performance from in-vitro dissolution data
- Measuring tablet color consistency
- Estimating storage stability only
- Replacing dissolution testing entirely
Correct Answer: Predicting in-vivo drug performance from in-vitro dissolution data
Q27. Which analytical technique is commonly used to quantify dissolved drug in samples?
- High-performance liquid chromatography (HPLC)
- Mass only without separation
- Direct weighing of dissolved drug mass
- pH meter readings alone
Correct Answer: High-performance liquid chromatography (HPLC)
Q28. A dissolution method is considered discriminatory if it:
- Produces identical profiles regardless of formulation changes
- Distinguishes between formulations with meaningful differences in release
- Never shows variability
- Is only useful for injectables
Correct Answer: Distinguishes between formulations with meaningful differences in release
Q29. Which factor can cause adsorption of drug onto the dissolution vessel or apparatus parts, altering results?
- Using glassware for highly lipophilic drugs without surface treatment
- Using disposable sterile syringes only
- Sampling at multiple time points only
- Using ultrapure water exclusively
Correct Answer: Using glassware for highly lipophilic drugs without surface treatment
Q30. What is dissolution efficiency (DE) used for?
- Quantifying the area under the dissolution curve as a single metric for comparison
- Measuring tablet hardness only
- Determining the melting point of excipients
- Calculating microbial load
Correct Answer: Quantifying the area under the dissolution curve as a single metric for comparison
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