Design approaches based on dissolution-controlled release focus on formulating dosage forms where the rate of drug release is governed primarily by dissolution from matrices or coatings. B.Pharm students should master matrix systems, reservoir systems with rate-controlling membranes, polymer selection (e.g., HPMC, ethylcellulose, Eudragit), release kinetics (zero-order, first-order, Higuchi, Korsmeyer–Peppas), in vitro dissolution testing, IVIVC, and factors like drug solubility, particle size, coating thickness, and sink conditions. Practical design balances targeted release profiles, stability, manufacturability, and regulatory considerations to avoid dose dumping. Mastering these concepts is essential for formulation development and regulatory submissions. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which mechanism most commonly governs drug release in dissolution-controlled matrix systems?
- Diffusion through a polymer matrix
- Bulk osmotic pumping
- Enzymatic degradation of excipients
- Ion-exchange resin displacement
Correct Answer: Diffusion through a polymer matrix
Q2. Which polymer is a widely used hydrophilic matrix former for dissolution-controlled tablets?
- Hydroxypropyl methylcellulose (HPMC)
- Ethylcellulose
- Eudragit RS
- Polyvinyl acetate
Correct Answer: Hydroxypropyl methylcellulose (HPMC)
Q3. A plot of cumulative drug released versus square root of time gives a straight line. Which model does this indicate?
- Higuchi model (square-root-of-time dependence)
- Zero-order release model
- Korsmeyer–Peppas with n = 1
- First-order release model
Correct Answer: Higuchi model (square-root-of-time dependence)
Q4. Which formulation approach is most associated with achieving near zero-order release independent of dissolution rate?
- Elementary osmotic pump system
- Immediate-release uncoated tablet
- pH-sensitive enteric-coated granules
- Ion-exchange resin beads
Correct Answer: Elementary osmotic pump system
Q5. Which change will typically decrease the dissolution rate of a solid drug from a tablet?
- Increase in drug particle size
- Increase in tablet surface area exposed to medium
- Use of a more soluble salt form
- Decrease in coating thickness
Correct Answer: Increase in drug particle size
Q6. In dissolution profile comparison, which similarity factor (f2) value indicates that two profiles are similar?
- f2 ≥ 50
- f2 ≤ 30
- f2 = 0
- f2 ≥ 100
Correct Answer: f2 ≥ 50
Q7. In the Korsmeyer–Peppas model for cylindrical tablets, an exponent n ≈ 0.45 indicates which mechanism?
- Fickian diffusion-controlled release
- Case II transport (polymer relaxation controlled)
- Pure erosion-controlled release
- Immediate burst release
Correct Answer: Fickian diffusion-controlled release
Q8. What is the practical definition of sink conditions in dissolution testing?
- The dissolved drug concentration remains below ~10% of its saturation solubility
- The medium pH is constant throughout the test
- The test is run at body temperature only
- The apparatus rotates at maximum speed
Correct Answer: The dissolved drug concentration remains below ~10% of its saturation solubility
Q9. Which excipient is commonly used to retard drug release by forming a hydrophobic matrix?
- Ethylcellulose
- Sodium starch glycolate
- Polyethylene glycol (PEG)
- Magnesium stearate (as lubricant)
Correct Answer: Ethylcellulose
Q10. What is the effect of increasing coating thickness of a rate-controlling membrane on dissolution-controlled release?
- Slower drug release due to longer diffusion path
- Faster drug release due to greater porosity
- No effect if coating polymer chemistry is unchanged
- Immediate burst release
Correct Answer: Slower drug release due to longer diffusion path
Q11. A weakly basic drug shows poor release in gastric fluid but improved release in intestinal pH. This is an example of:
- pH-dependent dissolution leading to variable GI release
- Osmotically driven release
- Temperature-dependent dissolution
- Ion-exchange controlled release
Correct Answer: pH-dependent dissolution leading to variable GI release
Q12. Which dissolution test parameter is most critical for reproducible results across laboratories?
- Agitation/stirring speed (rpm)
- Ambient room lighting
- Tablet color
- Time of day when test conducted
Correct Answer: Agitation/stirring speed (rpm)
Q13. One advantage of multiparticulate (bead or pellet) dissolution-controlled systems over single-unit tablets is:
- Reduced risk of dose dumping and more uniform GI transit
- Lower manufacturing complexity always
- Guaranteed zero-order release in all patients
- Complete avoidance of first-pass metabolism
Correct Answer: Reduced risk of dose dumping and more uniform GI transit
Q14. Which assumption is made in deriving the classical Higuchi equation for matrix release?
- Initial drug concentration in the matrix is much higher than drug solubility (C0 >> Cs)
- Drug undergoes enzymatic degradation in the matrix
- Release is controlled solely by erosion of the matrix
- The medium is non-sink and saturated at time zero
Correct Answer: Initial drug concentration in the matrix is much higher than drug solubility (C0 >> Cs)
Q15. Which analytical technique is commonly used to characterize pore size distribution and porosity of a matrix affecting dissolution?
- Mercury intrusion porosimetry
- High-performance liquid chromatography (HPLC)
- Optical polarimetry
- Titration with NaOH
Correct Answer: Mercury intrusion porosimetry
Q16. Which polymer is an anionic methacrylate that dissolves at intestinal pH and is used for pH-dependent coatings?
- Eudragit L
- Polyvinylpyrrolidone (PVP)
- Hydroxypropyl cellulose (HPC)
- Ethylcellulose
Correct Answer: Eudragit L
Q17. The primary role of a plasticizer in a polymer coating for dissolution-controlled tablets is to:
- Increase film flexibility and reduce brittleness
- Increase drug solubility in the core
- Act as a disintegrant to speed release
- Neutralize acidic drugs
Correct Answer: Increase film flexibility and reduce brittleness
Q18. The Korsmeyer–Peppas model is most useful for which purpose in dissolution-controlled formulation analysis?
- Determining the mechanism of drug release from polymeric systems
- Measuring tablet hardness
- Quantifying residual solvents
- Predicting taste masking efficiency
Correct Answer: Determining the mechanism of drug release from polymeric systems
Q19. Which drug property makes design of a dissolution-controlled sustained release formulation most challenging?
- Very high aqueous solubility
- Extremely low potency requiring microgram dosing
- High molecular weight greater than 1000 Da
- Poor permeability but low solubility
Correct Answer: Very high aqueous solubility
Q20. Which experimental change will generally accelerate dissolution rate in an in vitro test?
- Increasing the dissolution medium temperature
- Decreasing paddle rotation speed
- Using a less soluble salt form
- Adding more hydrophobic binder into the tablet
Correct Answer: Increasing the dissolution medium temperature
Q21. A well-developed dissolution method for controlled-release products must be discriminatory. What does “discriminatory” mean here?
- It can detect meaningful formulation or process changes that affect release
- It provides identical results across all product batches regardless of change
- It always produces a linear calibration curve
- It measures only the total drug content, not rate
Correct Answer: It can detect meaningful formulation or process changes that affect release
Q22. Coatings that incorporate water-soluble pore formers create dissolution channels. Which is a commonly used pore-former?
- Polyethylene glycol (PEG) 4000
- Ethylcellulose (as sole coating polymer)
- Triethyl citrate at high concentration
- Magnesium stearate
Correct Answer: Polyethylene glycol (PEG) 4000
Q23. Which statement best describes a Level A in vitro–in vivo correlation (IVIVC)?
- Point-to-point correlation between in vitro dissolution and in vivo absorption rate
- A single scalar correlation of AUC only
- Qualitative similarity of Tmax values
- Comparison of tablet hardness to bioavailability
Correct Answer: Point-to-point correlation between in vitro dissolution and in vivo absorption rate
Q24. Which of the following systems is primarily dissolution/diffusion-controlled rather than osmotic-driven?
- Hydrophilic matrix tablet (e.g., HPMC matrix)
- Elementary osmotic pump tablet
- Mechanical implant with active pump
- Pulsatile reservoir with mechanical trigger
Correct Answer: Hydrophilic matrix tablet (e.g., HPMC matrix)
Q25. Swellable polymer matrix tablets commonly exhibit which overall release mechanism?
- Anomalous (non-Fickian) transport combining diffusion and polymer relaxation/erosion
- Purely first-order dissolution throughout the test
- Immediate complete release within minutes
- Exclusive ion-exchange mediated release
Correct Answer: Anomalous (non-Fickian) transport combining diffusion and polymer relaxation/erosion
Q26. The addition of surfactants to the dissolution medium is intended to:
- Improve wetting and apparent solubility of poorly soluble drugs
- Decrease the pH of the medium
- Increase tablet hardness
- Prevent polymer film formation
Correct Answer: Improve wetting and apparent solubility of poorly soluble drugs
Q27. Which polymer property most directly influences small-molecule diffusivity through a swelling polymer matrix?
- Glass transition temperature (Tg) affecting chain mobility
- Color of the polymer
- Density of the tablet press
- Drug melting point
Correct Answer: Glass transition temperature (Tg) affecting chain mobility
Q28. For a weakly acidic drug, how does increasing the dissolution medium pH typically affect dissolution rate?
- Higher pH increases ionization and solubility, thus faster dissolution
- Higher pH always decreases dissolution rate due to polymer swelling
- There is no effect of pH on dissolution rate
- Higher pH converts drug to a neutral form and reduces solubility
Correct Answer: Higher pH increases ionization and solubility, thus faster dissolution
Q29. Which in situ analytical technique allows real-time monitoring of drug concentration during dissolution testing?
- UV fiber-optic probe (in situ UV monitoring)
- Off-line HPLC sampling only
- Thermogravimetric analysis (TGA)
- X-ray crystallography
Correct Answer: UV fiber-optic probe (in situ UV monitoring)
Q30. Which is a notable disadvantage of dissolution-controlled sustained-release matrix tablets in clinical practice?
- Difficulty adjusting dose and potential for accumulation in patients with altered clearance
- Guaranteed improved bioavailability in all cases
- No regulatory requirements for dissolution testing
- They are always cheaper to manufacture than immediate-release tablets
Correct Answer: Difficulty adjusting dose and potential for accumulation in patients with altered clearance
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com