Gastro-retentive DDS: principles and concepts MCQs With Answer

Gastro-retentive DDS: principles and concepts MCQs With Answer is designed to help M. Pharm students master the science of retaining dosage forms in the stomach to enhance therapeutic outcomes. Gastro-retentive drug delivery systems (GRDDS) exploit physiological and formulation strategies such as buoyancy, mucoadhesion, expansion, and high-density approaches to prolong gastric residence time. This blog presents 20 well-crafted MCQs that probe essential principles: gastric motility and the MMC, fed/fasted physiology, formulation variables (polymers, gas-generating agents, density, size, shape), in vitro/in vivo evaluation, and clinical suitability. By engaging with these questions and answers, students will deepen their understanding of how GRDDS improves bioavailability for drugs with narrow absorption windows, enables local stomach targeting, and mitigates dosing fluctuations.

Q1. The primary objective of a gastro-retentive drug delivery system (GRDDS) is to

• Increase the permeability of the intestinal epithelium
• Prolong gastric residence to enhance drug absorption window
• Bypass first-pass metabolism via lymphatic uptake
• Accelerate gastric emptying to reduce variability

Correct Answer: Prolong gastric residence to enhance drug absorption window

Q2. Which physiological state most favors prolonged gastric retention of solid dosage forms?

• Fasted state with active phase III MMC
• Fed state with high-fat meal
• Severe diarrhea
• High gastric pH induced by proton pump inhibitors

Correct Answer: Fed state with high-fat meal

Q3. Floating drug delivery systems achieve gastric retention primarily by

• Increasing desorption rate from mucin
• Lowering system density below that of gastric fluid
• Tight junction modulation in the duodenum
• Inhibiting pyloric sphincter contractions

Correct Answer: Lowering system density below that of gastric fluid

Q4. The migrating myoelectric complex (MMC) in the fasted state is most associated with

• Expulsion of indigestible solids during phase III
• Continuous gastric mixing with minimal emptying
• Enhanced mucoadhesion due to thick mucus layer
• Suppression of gastric acid secretion

Correct Answer: Expulsion of indigestible solids during phase III

Q5. Effervescent floating systems commonly use which pair of agents to generate buoyant CO₂ in gastric fluid?

• Sodium bicarbonate and citric/tartaric acid
• Calcium carbonate and magnesium stearate
• Sodium chloride and lactose
• Potassium sorbate and povidone

Correct Answer: Sodium bicarbonate and citric/tartaric acid

Q6. Non-effervescent floating systems typically achieve buoyancy using

• High-density metal oxides dispersed in the core
• Hydrophilic swellable polymers like HPMC or PEO
• Surfactants that reduce mucin viscosity
• Enteric polymers that dissolve in the intestine

Correct Answer: Hydrophilic swellable polymers like HPMC or PEO

Q7. High-density gastro-retentive systems aim for a density typically

• Below 0.8 g/cm³
• Approximately equal to gastric fluid (~1.0 g/cm³)
• Between 1.2–1.5 g/cm³
• ≥ 2.5 g/cm³

Correct Answer: ≥ 2.5 g/cm³

Q8. Mucoadhesive gastro-retentive systems benefit in the stomach from polymers such as chitosan because

• Chitosan is cationic and electrostatically interacts with negatively charged mucin
• Chitosan is hydrophobic and avoids mucus layer penetration
• Chitosan dissolves instantly to form micelles
• Chitosan is an effervescent salt generating CO₂

Correct Answer: Chitosan is cationic and electrostatically interacts with negatively charged mucin

Q9. Drugs most suitable for GRDDS are those that

• Are unstable in acidic pH and absorbed in the colon
• Have a narrow absorption window in the stomach/upper small intestine
• Exhibit enteric protection requirements
• Are substrates of P-gp in the distal ileum

Correct Answer: Have a narrow absorption window in the stomach/upper small intestine

Q10. An expandable (unfolding) GRDDS improves retention by

• Reducing surface area to slow drug release
• Expanding to a size that prevents pyloric passage until erosion
• Neutralizing gastric acid to delay emptying
• Increasing gastric motility via cholinergic effects

Correct Answer: Expanding to a size that prevents pyloric passage until erosion

Q11. Which in vitro parameter pair is standard for evaluating floating behavior of GRDDS tablets?

• Wetting time and bioadhesive strength
• Floating lag time and total floating time
• Contact angle and tensile strength
• Friability and hardness

Correct Answer: Floating lag time and total floating time

Q12. A typical medium used to assess buoyancy and release of GRDDS in vitro is

• Phosphate buffer pH 6.8 at 25°C
• Distilled water at 37°C
• 0.1 N HCl at 37°C
• Simulated intestinal fluid without enzymes at 32°C

Correct Answer: 0.1 N HCl at 37°C

Q13. Which combination best characterizes raft-forming systems?

• Ethyl cellulose matrices forming non-swelling barriers
• Sodium alginate with bicarbonate forming a low-density gel for GERD
• PEO-based systems with osmotic pumping
• Enteric polymers creating pH-sensitive ion exchange

Correct Answer: Sodium alginate with bicarbonate forming a low-density gel for GERD

Q14. The most relevant in vivo method to track gastric residence time of GRDDS is

• UV–Vis spectroscopy of plasma samples
• Gamma scintigraphy using a radiolabel
• Differential scanning calorimetry
• Particle size analysis by laser diffraction

Correct Answer: Gamma scintigraphy using a radiolabel

Q15. Which factor generally increases gastric residence of single-unit systems under fed conditions?

• Smaller geometric size
• Larger geometric size
• Highly negative zeta potential
• High porosity regardless of size

Correct Answer: Larger geometric size

Q16. A key advantage of multiple-unit (multiparticulate) GRDDS over single-unit systems is

• Higher risk of dose dumping
• Less inter-subject variability and lower obstruction risk
• Exclusive suitability for high-dose drugs
• Complete independence from fed/fasted state

Correct Answer: Less inter-subject variability and lower obstruction risk

Q17. Which statement about drug release from hydrophilic matrix-based floating tablets is most accurate?

• Release is solely erosion-controlled
• Release is governed by combined diffusion and polymer erosion
• Release is independent of polymer viscosity grade
• Release proceeds only by osmotic pumping

Correct Answer: Release is governed by combined diffusion and polymer erosion

Q18. Contraindications for GRDDS generally include patients with

• Gastrointestinal obstruction or severe motility disorders
• Normal gastric emptying and intact mucosa
• Mild lactose intolerance
• Low-dose, acid-stable medications

Correct Answer: Gastrointestinal obstruction or severe motility disorders

Q19. Which of the following is NOT a commonly cited theory of mucoadhesion?

• Diffusion (interpenetration) theory
• Electronic theory
• Adsorption theory
• Photolysis theory

Correct Answer: Photolysis theory

Q20. An example of a drug class that benefits from GRDDS due to local stomach targeting is

• Antiarrhythmics for ventricular fibrillation
• Antibiotics for Helicobacter pylori eradication
• Anthelmintics for tissue nematodes
• Thyroid hormones for systemic replacement

Correct Answer: Antibiotics for Helicobacter pylori eradication

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