Gastroretentive drug delivery systems (GRDDS) are advanced oral formulations designed to prolong gastric residence time, improving absorption and therapeutic efficacy for drugs with a narrow absorption window, local gastric action, or poor intestinal stability. GRDDS concepts include floating (effervescent and non-effervescent), mucoadhesive, high-density, expandable and superporous systems that exploit buoyancy, adhesion, density and swelling mechanisms. Key formulation components are swelling polymers (HPMC, sodium alginate, chitosan), gas-generating agents (sodium bicarbonate), and mucoadhesive polymers (carbopol). Understanding physiological factors (gastric motility, fed/fasted state, pH), in vitro tests (buoyancy lag time, swelling index) and in vivo evaluation (gamma scintigraphy) is essential for design and optimization. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary aim of gastroretentive drug delivery systems (GRDDS)?
- To increase drug solubility in the intestine
- To prolong the gastric residence time of a dosage form
- To enhance renal elimination of drugs
- To reduce drug stability in stomach
Correct Answer: To prolong the gastric residence time of a dosage form
Q2. Which category of drugs most benefits from GRDDS?
- Drugs with wide absorption window throughout the GI tract
- Drugs unstable in acidic stomach environment
- Drugs with narrow absorption window in the upper GI tract
- Drugs exclusively absorbed in the colon
Correct Answer: Drugs with narrow absorption window in the upper GI tract
Q3. Which of the following is NOT a common type of GRDDS?
- Floating (buoyant) systems
- Mucoadhesive systems
- Colon-targeted time-dependent systems
- High-density sinking systems
Correct Answer: Colon-targeted time-dependent systems
Q4. What is the principal mechanism by which effervescent floating systems remain in the stomach?
- Adhesion to gastric mucosa
- Generation of CO2 gas reducing overall density (buoyancy)
- Conversion to insoluble precipitate
- Rapid disintegration into large particles
Correct Answer: Generation of CO2 gas reducing overall density (buoyancy)
Q5. Which gas-generating agent is most commonly used in effervescent floating GRDDS?
- Sodium chloride
- Sodium bicarbonate
- Calcium carbonate
- Magnesium hydroxide
Correct Answer: Sodium bicarbonate
Q6. Which polymer is widely used as a hydrophilic matrix former for non-effervescent floating systems?
- HPMC (Hydroxypropyl methylcellulose)
- Polydimethylsiloxane
- Polyethylene glycol 400
- Sodium lauryl sulfate
Correct Answer: HPMC (Hydroxypropyl methylcellulose)
Q7. Which polymer is known for mucoadhesive properties commonly used in mucoadhesive GRDDS?
- Chitosan
- Polystyrene
- Ethyl cellulose
- Polyvinyl chloride
Correct Answer: Chitosan
Q8. What approximate density should an ideal floating GRDDS have to remain buoyant on gastric fluid?
- Greater than 1.5 g/cm³
- Less than 1.0 g/cm³
- Between 2.0–3.0 g/cm³
- Equal to 1.5 g/cm³
Correct Answer: Less than 1.0 g/cm³
Q9. High-density (sinking) gastroretentive systems are designed to have density typically greater than:
- 0.8 g/cm³
- 1.0 g/cm³
- 1.5 g/cm³
- 2.5 g/cm³
Correct Answer: 2.5 g/cm³
Q10. What does the ‘swelling index’ of a GRDDS formulation measure?
- Amount of drug dissolved per minute
- Increase in volume or weight due to water uptake over time
- Change in pH of gastric fluid
- Rate of polymer degradation
Correct Answer: Increase in volume or weight due to water uptake over time
Q11. How does the fed state affect gastric residence time (GRT) of GRDDS compared to the fasted state?
- Fed state usually shortens GRT
- Fed state has no effect on GRT
- Fed state usually prolongs GRT
- GRT is only determined by drug solubility
Correct Answer: Fed state usually prolongs GRT
Q12. Which characteristic makes a drug a good candidate for GRDDS?
- Extensive absorption in the colon
- Complete absorption throughout the GI tract
- Narrow absorption window in the proximal small intestine
- High stability in alkaline pH only
Correct Answer: Narrow absorption window in the proximal small intestine
Q13. Which in vitro test measures the time required for a floating tablet to rise to the surface of the dissolution medium?
- Swelling index test
- Buoyancy lag time test
- Disintegration time test
- Hardness test
Correct Answer: Buoyancy lag time test
Q14. Raft-forming GRDDS typically employ which biopolymer to form a cohesive gel in acidic gastric environment?
- Sodium alginate
- Polypropylene
- Polyethylene terephthalate
- Methyl methacrylate
Correct Answer: Sodium alginate
Q15. Which mathematical model is commonly used to describe diffusion-controlled drug release from GRDDS matrices?
- Higuchi model
- Michaelis–Menten model
- Arrhenius equation
- Beckmann model
Correct Answer: Higuchi model
Q16. Which imaging technique is widely used for in vivo evaluation of gastric residence time of GRDDS?
- Magnetic resonance imaging (MRI)
- Gamma scintigraphy
- Infrared spectroscopy
- Ultraviolet-visible spectrophotometry
Correct Answer: Gamma scintigraphy
Q17. Superporous hydrogels are particularly useful in GRDDS because they:
- Have very low swelling capacity
- Rapidly absorb water and swell due to interconnected large pores
- Sink immediately in gastric fluid
- Prevent any drug release in stomach
Correct Answer: Rapidly absorb water and swell due to interconnected large pores
Q18. Which is a major limitation of gastroretentive systems?
- They eliminate intersubject variability
- They always work well in hypochlorhydric patients
- Variability in gastric emptying and physiological conditions can affect performance
- They guarantee 100% bioavailability
Correct Answer: Variability in gastric emptying and physiological conditions can affect performance
Q19. Which design strategy helps prevent premature gastric emptying of a single-unit GRDDS?
- Reducing size to less than 2 mm
- Using a rapidly dissolving polymer
- Increasing size or using expandable systems to exceed pyloric opening
- Formulating as highly soluble granules
Correct Answer: Increasing size or using expandable systems to exceed pyloric opening
Q20. What is the primary function of HPMC in many GRDDS formulations?
- To act as an effervescent agent
- To provide hydrophilic matrix formation, swelling and controlled release
- To increase drug crystallinity
- To act as a lubricating agent only
Correct Answer: To provide hydrophilic matrix formation, swelling and controlled release
Q21. In alginate-based raft systems, gelation and raft formation is promoted by interaction with which ion in gastric fluid?
- Sodium (Na+)
- Potassium (K+)
- Calcium (Ca2+)
- Chloride (Cl-)
Correct Answer: Calcium (Ca2+)
Q22. Buoyancy lag time is defined as:
- The time required for complete drug release
- The time until the dosage form begins to float on the medium
- The time taken for tablet disintegration
- The time to reach maximum swelling
Correct Answer: The time until the dosage form begins to float on the medium
Q23. Which physiological condition can reduce the gas generation and buoyancy of effervescent floating systems?
- Hypochlorhydria or increased gastric pH
- Enhanced gastric acidity (low pH)
- Increased gastric fluid volume with normal acidity
- Decreased gastric motility only
Correct Answer: Hypochlorhydria or increased gastric pH
Q24. Which in vitro method is commonly used to evaluate mucoadhesive strength of GRDDS?
- Wash-off test using mucosal tissue
- Dissolution test in phosphate buffer only
- UV-Visible colorimetric assay
- Thermogravimetric analysis
Correct Answer: Wash-off test using mucosal tissue
Q25. Expandable GRDDS retain in the stomach primarily by:
- Reducing their size on contact with gastric fluid
- Binding to dietary proteins
- Expanding to a size that prevents passage through the pylorus
- Rapidly disintegrating into small particles
Correct Answer: Expanding to a size that prevents passage through the pylorus
Q26. Which is a key therapeutic advantage of successfully formulated GRDDS?
- Reduced drug residence time in stomach
- Improved bioavailability and reduced dosing frequency for suitable drugs
- Guaranteed colon targeting
- Universal suitability for all drugs
Correct Answer: Improved bioavailability and reduced dosing frequency for suitable drugs
Q27. Which type of drug is generally NOT suitable for GRDDS?
- Drugs with narrow absorption window in the proximal small intestine
- Drugs degraded in intestinal alkaline pH
- Drugs unstable in acidic gastric environment
- Drugs with local gastric action
Correct Answer: Drugs unstable in acidic gastric environment
Q28. Which polymer is commonly used for strong mucoadhesion and bioadhesive matrix in GRDDS?
- Carbopol (carbomer)
- Polystyrene
- Polyethylene
- Polylactic acid
Correct Answer: Carbopol (carbomer)
Q29. Why is establishing an in vitro–in vivo correlation (IVIVC) important for GRDDS development?
- To eliminate the need for formulation optimization
- To predict in vivo performance from in vitro tests and support formulation scale-up
- To ensure the product floats indefinitely in vitro
- To increase the cost of development
Correct Answer: To predict in vivo performance from in vitro tests and support formulation scale-up
Q30. Regulatory demonstration of prolonged gastric retention for a GRDDS often requires which type of evidence?
- Only dissolution data in water
- In vivo imaging or pharmacokinetic studies showing extended GRT or absorption
- Only visual inspection of tablets
- Only in vitro hardness testing
Correct Answer: In vivo imaging or pharmacokinetic studies showing extended GRT or absorption
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.
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