Gastroretentive drug delivery systems (GRDDS) extend gastric residence time of oral dosage forms to improve absorption, bioavailability and therapeutic outcomes for drugs with narrow absorption windows. This introduction reviews advantages — such as enhanced bioavailability, localized stomach delivery, reduced dosing frequency and controlled release — and disadvantages like variable gastric retention, food effects, manufacturing complexity and risk of obstruction. Key GRDDS types include floating, mucoadhesive, expandable and high-density systems; important formulation aspects include polymer selection (HPMC, Carbopol, chitosan), buoyancy mechanisms, swelling behavior and in vitro evaluation (floating lag time, total floating time). Simple, practical insights for B.Pharm students will help in formulation design and critical appraisal. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary objective of a gastroretentive drug delivery system (GRDDS)?
- To decrease drug stability in the stomach
- To prolong gastric residence time for improved drug absorption
- To increase drug clearance via the kidneys
- To avoid systemic absorption completely
Correct Answer: To prolong gastric residence time for improved drug absorption
Q2. Which of the following drugs is most suitable for GRDDS?
- A drug with extensive absorption in the colon
- A drug with narrow absorption window in the upper GI tract
- A drug primarily absorbed in the rectum
- A drug with uniform absorption throughout the GI tract
Correct Answer: A drug with narrow absorption window in the upper GI tract
Q3. Which mechanism is used by floating GRDDS to remain in the stomach?
- High density greater than gastric contents
- Adhesion to intestinal villi
- Buoyancy by gas generation or low-density matrices
- Rapid erosion in gastric fluid
Correct Answer: Buoyancy by gas generation or low-density matrices
Q4. Which polymer is commonly used to impart buoyancy and controlled release in floating tablets?
- Sodium lauryl sulfate
- HPMC (hydroxypropyl methylcellulose)
- Polyethylene glycol 400
- Magnesium stearate
Correct Answer: HPMC (hydroxypropyl methylcellulose)
Q5. Mucoadhesive GRDDS rely on which interaction to retain the dosage form in the stomach?
- Hydrophobic interactions with food particles
- Ionic or hydrogen bonding with gastric mucin
- Enzymatic digestion of the dosage form
- Magnetic attraction to gastric lining
Correct Answer: Ionic or hydrogen bonding with gastric mucin
Q6. A major advantage of GRDDS is:
- Uniform gastric emptying in all patients
- Reduced bioavailability of poorly soluble drugs
- Improved bioavailability for drugs absorbed in the stomach/upper intestine
- Guaranteed retention irrespective of fed or fasted state
Correct Answer: Improved bioavailability for drugs absorbed in the stomach/upper intestine
Q7. Which evaluation parameter measures how quickly a floating dosage form begins to float?
- Total floating time
- Floating lag time
- Disintegration time in colon
- Swelling index after 24 hours
Correct Answer: Floating lag time
Q8. Which of the following is a disadvantage commonly associated with GRDDS?
- Predictable retention in all physiological conditions
- Risk of gastric irritation or obstruction with expandable systems
- Simple manufacturing without scale-up issues
- No influence of meal composition on performance
Correct Answer: Risk of gastric irritation or obstruction with expandable systems
Q9. High-density GRDDS are designed to do what in the stomach?
- Float on gastric fluid by generating gas
- Adhere to mucosa by swelling
- Sink to the lower stomach wall and resist gastric emptying
- Rapidly disintegrate for immediate release
Correct Answer: Sink to the lower stomach wall and resist gastric emptying
Q10. Which excipient is commonly used as an effervescent agent in gas-generating floating systems?
- Calcium carbonate
- Sodium bicarbonate
- Magnesium oxide
- Poloxamer 188
Correct Answer: Sodium bicarbonate
Q11. Swelling/expandable GRDDS prolong gastric residence mainly by:
- Reducing tablet size after administration
- Expanding to a size that prevents passage through the pylorus
- Becoming denser than gastric contents
- Dissolving quickly in gastric juice
Correct Answer: Expanding to a size that prevents passage through the pylorus
Q12. Which in vitro test assesses matrix integrity and buoyant behavior simultaneously?
- Floating lag time and total floating time test
- Disintegration test in pH 7.4 buffer
- Sterility testing in simulated gastric fluid
- Osmotic pressure measurement
Correct Answer: Floating lag time and total floating time test
Q13. Food intake affects GRDDS performance by:
- Eliminating variability in gastric retention
- Altering gastric emptying time and motility, often increasing retention
- Preventing polymer hydration completely
- Reducing stomach volume only during fasting
Correct Answer: Altering gastric emptying time and motility, often increasing retention
Q14. Which drug characteristic decreases suitability for GRDDS?
- Narrow absorption window in the upper GI tract
- Instability in acidic pH
- Poor systemic side effects
- Low dose requirement
Correct Answer: Instability in acidic pH
Q15. A mucoadhesive polymer commonly used in GRDDS is:
- Carbopol
- Propylene glycol
- Magnesium stearate
- Ethyl cellulose
Correct Answer: Carbopol
Q16. Controlled-release GRDDS can reduce which of the following?
- Drug solubility in gastric fluid
- Dosing frequency and peak-trough fluctuations
- Need for polymer selection
- Manufacturing complexity
Correct Answer: Dosing frequency and peak-trough fluctuations
Q17. Which physicochemical property of a drug favors absorption in the stomach?
- PKa resulting in ionization at gastric pH and poor permeability
- Acidic drug with higher stability and solubility at low pH
- Highly lipophilic with zero solubility at pH 1–2
- Drug that degrades rapidly in acidic medium
Correct Answer: Acidic drug with higher stability and solubility at low pH
Q18. Which is an important scale-up/manufacturing challenge for GRDDS?
- Ensuring identical magnetic properties at large scale
- Maintaining consistent buoyancy and matrix integrity batch-to-batch
- Eliminating all polymer content to reduce cost
- Preventing drug absorption in the stomach
Correct Answer: Maintaining consistent buoyancy and matrix integrity batch-to-batch
Q19. In GRDDS formulation, what is the role of gas-generating components?
- Increase tablet density to make it sink
- Generate CO2 to decrease tablet density and induce buoyancy
- Act as disintegrants to speed dissolution
- Neutralize gastric acid to increase pH
Correct Answer: Generate CO2 to decrease tablet density and induce buoyancy
Q20. Which evaluation parameter indicates how long a floating system remains buoyant?
- Floating lag time
- Total floating time
- Disintegration time in intestinal fluid
- Surface pH measurement
Correct Answer: Total floating time
Q21. Which GRDDS type uses polymers that form a gel layer to control release while floating?
- High-density sinking systems
- Non-gel forming immediate release tablets
- Hydrodynamically balanced systems (HBS) / floating matrix systems
- Rectal suppositories
Correct Answer: Hydrodynamically balanced systems (HBS) / floating matrix systems
Q22. A disadvantage related to patient variability in GRDDS is:
- Uniform gastric pH among all patients
- Interindividual differences in gastric emptying and motility affecting retention
- Guaranteed drug absorption in fasted state
- Elimination of drug-food interactions
Correct Answer: Interindividual differences in gastric emptying and motility affecting retention
Q23. Which mathematical model is commonly used to describe controlled release from polymer matrices?
- Michaelis-Menten kinetics
- Higuchi model
- Arrhenius equation
- Lambert-Beer law
Correct Answer: Higuchi model
Q24. Which formulation strategy can reduce the risk of gastric obstruction with expandable GRDDS?
- Using non-biodegradable rigid scaffolds
- Designing systems that biodegrade or reduce size after a set time
- Maximizing permanent expansion to the largest possible size
- Eliminating any polymer to avoid swelling
Correct Answer: Designing systems that biodegrade or reduce size after a set time
Q25. For a GRDDS targeted to treat H. pylori infection, the main advantage is:
- Systemic delivery to avoid local gastric effects
- Localized high drug concentration at the gastric mucosa
- Delivery to the colon for extended retention
- Complete avoidance of acidic degradation
Correct Answer: Localized high drug concentration at the gastric mucosa
Q26. Which lab assessment helps predict in vivo gastric retention of GRDDS?
- In vitro floating behavior combined with swelling and mucoadhesion tests
- Serum protein binding assay
- Liver microsomal stability test
- Partition coefficient in octanol only
Correct Answer: In vitro floating behavior combined with swelling and mucoadhesion tests
Q27. Which of the following is a typical polymer used for mucoadhesion in GRDDS?
- Sucrose
- Carboxymethyl cellulose (CMC) or chitosan
- Sodium chloride
- Polystyrene
Correct Answer: Carboxymethyl cellulose (CMC) or chitosan
Q28. Why are low-dose drugs often preferable candidates for GRDDS?
- They always degrade in gastric acid
- Small dosage forms are easier to retain by expansion or buoyancy
- High dose forms are simpler to formulate
- Low-dose drugs require complex surgical implants
Correct Answer: Small dosage forms are easier to retain by expansion or buoyancy
Q29. Which regulatory consideration is particularly important for GRDDS?
- Demonstration of in vitro–in vivo correlation (IVIVC) for gastric retention and release
- Proof that the product dissolves within 5 minutes in all media
- Exclusion of any polymeric excipient
- Showing no interaction with swallowed saliva only
Correct Answer: Demonstration of in vitro–in vivo correlation (IVIVC) for gastric retention and release
Q30. The term “floating lag time” should ideally be:
- As long as possible to delay floating
- Short, so the dosage form quickly attains buoyancy
- Irrelevant for floating systems
- Equal to total floating time
Correct Answer: Short, so the dosage form quickly attains buoyancy
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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