Formulation and Evaluation of Gastroretentive Drug Delivery Systems: A Comprehensive and Updated Review

Abstract

Gastro-retentive drug delivery systems (GRDDS) represent an advanced strategy to enhance the oral bioavailability of drugs exhibiting narrow absorption windows, pH-dependent solubility, or localized gastric action. This review provides a comprehensive and critical overview of GRDDS, including physiological considerations, formulation approaches, and classification of systems such as floating, mucoadhesive, expandable, and high-density systems. Recent technological advancements including 3D printing, nanotechnology integration, biopolymer-based raft systems, and artificial intelligence-driven formulation design are highlighted. Furthermore, key challenges such as variability in gastric retention, limited in vivo predictability, and regulatory constraints are discussed. The review concludes with future perspectives focusing on personalized drug delivery and smart gastro-retentive platforms.

Keywords

Gastroretentive systems, floating drug delivery, mucoadhesion, 3D printing, controlled release, bioavailability

Introduction

4. SINGLE UNIT VS MULTIPLE UNIT SYSTEMS IN GRDDS

Gastro-retentive drug delivery systems (GRDDS) can be broadly categorized into single-unit dosage forms (SUDFs) and multiple-unit dosage forms (MUDFs) based on their structural design and distribution within the gastrointestinal tract. This classification plays a crucial role in determining gastric retention behavior, drug release kinetics, and overall therapeutic performance (Tripathi et al., 2019; Kumar et al., 2024).

4.1 Single-Unit Dosage Forms (SUDFs)

Single-unit systems consist of a single compact structure, such as tablets or capsules, designed to remain in the stomach for prolonged periods.

Characteristics

• Typically larger in size
• Designed as floating, expandable, or bioadhesive systems
• Provide controlled or sustained drug release

Advantages

• High dose uniformity: Entire drug dose is contained in a single unit
• Simpler manufacturing process
• Easier formulation optimization

Limitations

• High risk of dose dumping: Failure of the system (e.g., premature disintegration) can release the entire drug dose at once
• Unpredictable gastric retention: May pass rapidly through the pylorus due to peristaltic movements
• Increased variability in drug absorption
• Potential local irritation due to concentrated drug release

Because of these limitations, SUDFs often exhibit poor reproducibility in vivo, particularly under fasted conditions (Streubel et al., 2006).

4.2 Multiple-Unit Dosage Forms (MUDFs)

Multiple-unit systems consist of numerous small discrete units, such as pellets, granules, microspheres, or beads, which are administered collectively.

Characteristics

• Uniform distribution throughout the stomach
• Reduced dependence on a single retention event
• Can be designed as floating, mucoadhesive, or swelling systems

Advantages

• Reduced risk of dose dumping: Failure of individual units does not affect the entire dose
• Improved gastric retention reliability: Smaller units distribute widely and are less likely to be expelled simultaneously
• Better reproducibility: More consistent drug absorption profiles
• Enhanced safety profile: Lower risk of local irritation

Limitations

• More complex manufacturing processes
• Challenges in ensuring uniform drug loading across units
• Higher production cost

MUDFs are increasingly preferred in modern GRDDS due to their superior performance, safety, and consistency, particularly in overcoming physiological variability (Mandal et al., 2016).

4.3 Comparative Analysis

Table 2: Comparison of single-unit and multiple-unit GRDDS in terms of performance, safety, and formulation characteristics.

Feature	Single Unit	Multiple Unit
Dose uniformity	High	Moderate
Risk of dose dumping	High	Low
Gastric retention reliability	Low	High
Reproducibility	Low	High
Safety	Moderate	High
Manufacturing complexity	Low	High

4.4 Critical Perspective

Although single-unit systems are simpler and cost-effective, their clinical application is limited by high variability and risk of failure. In contrast, multiple-unit systems offer robust and reliable performance, making them more suitable for achieving consistent therapeutic outcomes.

Recent research trends emphasize the development of hybrid MUDF-based GRDDS, such as floating microspheres and mucoadhesive beads, which combine multiple retention mechanisms to further enhance efficacy. These systems are particularly promising for controlled drug delivery and targeted gastric therapy (Hua, 2020; Shah et al., 2025).

5. RECENT ADVANCES IN GASTRORETENTIVE DRUG DELIVERY SYSTEMS (2020–2026)

Recent advancements in gastro-retentive drug delivery systems (GRDDS) have been driven by the need for precision medicine, improved therapeutic efficacy, and patient-specific treatment strategies. Modern GRDDS research integrates material science, digital manufacturing, nanotechnology, and computational modeling to overcome limitations associated with conventional systems. These innovations have transformed GRDDS into multifunctional, intelligent drug delivery platforms capable of controlled, targeted, and responsive drug release (Zhang et al., 2025; Dubey et al., 2025).

5.1 3D Printing Technology in GRDDS

Three-dimensional (3D) printing has emerged as a revolutionary tool in pharmaceutical manufacturing, enabling the fabrication of complex and customizable dosage forms with precise control over geometry, density, and internal structure.

Key Features

• Fabrication of floating tablets with controlled porosity
• Development of multi-layered and multi-drug systems
• Tailoring of drug release profiles based on patient needs

Technologies Used

• Fused Deposition Modeling (FDM)
• Stereolithography (SLA)
• Selective Laser Sintering (SLS)

Advantages

• Personalized medicine (patient-specific dosing)
• Precise control over floating lag time and buoyancy
• Improved reproducibility

Recent studies demonstrate that 3D-printed GRDDS exhibit enhanced gastric retention, programmable drug release kinetics, and improved bioavailability, making them highly promising for future clinical applications (Alqahtani et al., 2026; Awad et al., 2021).

5.2 Nanotechnology Integration

Nanotechnology has significantly enhanced the functionality of GRDDS by enabling drug encapsulation at the nanoscale, improving solubility, stability, and targeting efficiency.

Types of Nanocarriers

• Polymeric nanoparticles
• Liposomes
• Solid lipid nanoparticles (SLNs)
• Nanoemulsions

Advantages

• Enhanced drug solubility and dissolution rate
• Improved mucosal penetration and targeting
• Controlled and sustained drug release
• Protection of drugs from degradation

Integration of nanoparticles into floating or mucoadhesive systems results in hybrid GRDDS, which combine prolonged gastric retention with targeted drug delivery. This approach is particularly beneficial for poorly water-soluble drugs and gastric infections (Grosso et al., 2022; Zhang et al., 2025).

5.3 Biopolymer-Based Raft Systems

Raft-forming systems represent an innovative GRDDS approach, particularly for the treatment of gastroesophageal reflux disease (GERD).

Mechanism

Upon contact with gastric fluid, these systems form a viscous gel (raft) that floats on the stomach contents, acting as a barrier to prevent reflux and enabling localized drug delivery.

Common Biopolymers

• Sodium alginate
• Pectin
• Chitosan

Advantages

• Excellent biocompatibility and biodegradability
• Localized drug action
• Improved patient compliance

Recent advancements focus on hybrid biopolymer systems and incorporation of active agents into raft matrices, enhancing both mechanical strength and drug release control (Bachhar et al., 2026; Patel et al., 2025).

5.4 Artificial Intelligence (AI) in Formulation Design

Artificial intelligence (AI) and machine learning (ML) are transforming pharmaceutical development by enabling data-driven optimization of GRDDS formulations.

Applications

• Prediction of optimal polymer combinations
• Optimization of floating lag time and swelling behavior
• Modeling of drug release kinetics and dissolution profiles
• Simulation of in vivo drug performance

Advantages

• Reduced experimental time and cost
• Enhanced formulation precision
• Improved reproducibility

AI-driven approaches allow researchers to analyze complex interactions between formulation variables and physiological conditions, leading to more robust and efficient GRDDS design (Shah et al., 2025; Rao et al., 2024).

5.5 Smart and Stimuli-Responsive Systems

Smart GRDDS utilize stimuli-responsive polymers that can adapt to environmental changes in the gastrointestinal tract.

Types of Stimuli

• pH-responsive systems: Trigger drug release at specific pH levels
• Temperature-sensitive systems: Respond to body temperature changes
• Enzyme-responsive systems: Release drugs in presence of specific enzymes

Advantages

• Site-specific drug delivery
• Reduced side effects
• Enhanced therapeutic efficiency

These systems enable on-demand drug release, making them highly suitable for chronic diseases requiring controlled and targeted therapy. Recent developments focus on multi-stimuli-responsive systems, which combine multiple triggers for enhanced precision (Yang et al., 2024; Hua, 2020).

5.6 Critical Perspective on Recent Advances

While these advancements have significantly improved GRDDS performance, several challenges remain:

• Scalability of 3D printing technologies
• Regulatory concerns for AI-driven formulations
• Stability issues in nanoparticle-based systems
• Limited clinical translation of smart systems

Future research should focus on bridging the gap between laboratory innovation and clinical application, ensuring safety, efficacy, and regulatory compliance.

6. APPLICATIONS OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS (GRDDS)

Gastro-retentive drug delivery systems (GRDDS) have gained significant attention due to their ability to enhance drug bioavailability, improve therapeutic efficacy, and enable site-specific drug delivery in the stomach and upper gastrointestinal tract. These systems are particularly useful for drugs with absorption limitations, stability issues, or localized gastric action requirements (Tripathi et al., 2019; Dubey et al., 2025).

6.1 Drugs with Narrow Absorption Window

GRDDS are highly beneficial for drugs that are primarily absorbed in the upper part of the gastrointestinal tract (stomach and proximal small intestine).

Examples

• Levodopa
• Riboflavin
• Furosemide

Significance

These drugs exhibit reduced absorption when they pass into the lower intestine. GRDDS prolong gastric residence time, ensuring maximum drug absorption within the optimal absorption window, thereby improving bioavailability and therapeutic outcomes (Kumar et al., 2024; Shah et al., 2025).

6.2 Drugs with Poor Solubility at Higher pH

Certain drugs exhibit pH-dependent solubility, where they dissolve better in acidic conditions of the stomach but poorly in the alkaline environment of the intestine.

Examples

• Ketoconazole
• Atazanavir
• Ciprofloxacin

Application

GRDDS maintain the drug in the acidic gastric environment, enhancing drug dissolution and absorption. This approach significantly improves the effectiveness of poorly soluble drugs (Hua, 2020; Zhang et al., 2025).

6.3 Localized Drug Delivery in the Stomach

GRDDS are particularly effective for drugs that require localized action in the gastric region, reducing systemic exposure and side effects.

Examples

• Antibiotics for Helicobacter pylori (e.g., amoxicillin, clarithromycin)
• Antacids and anti-ulcer drugs

Advantages

• Increased drug concentration at the site of infection
• Improved eradication rates
• Reduced systemic toxicity

Floating and mucoadhesive systems are especially useful for targeted gastric therapy (Mandal et al., 2016; Patel et al., 2025).

6.4 Controlled and Sustained Drug Release

GRDDS enable controlled drug release over an extended period, reducing dosing frequency and improving patient compliance.

Benefits

• Stable plasma drug concentration
• Reduced fluctuations in drug levels
• Minimized side effects

This application is particularly useful for chronic diseases requiring long-term therapy, such as hypertension and Parkinson’s disease (Singh & Das, 2024; Pawar et al., 2011).

6.5 Improvement of Bioavailability of Poorly Absorbed Drugs

Many drugs suffer from low bioavailability due to rapid gastric transit or degradation in the intestinal environment.

GRDDS improve bioavailability by:

• Prolonging gastric residence time
• Enhancing drug dissolution
• Protecting drugs from degradation

This is especially beneficial for biopharmaceutical classification system (BCS) class II and III drugs (Zhang et al., 2025; Dubey et al., 2025).

6.6 Application in Gastroesophageal Reflux Disease (GERD)

Raft-forming GRDDS are widely used in the treatment of GERD.

Mechanism

These systems form a floating gel barrier on gastric contents, preventing acid reflux into the esophagus.

Examples

• Alginate-based formulations (e.g., Gaviscon)

Advantages

• Rapid symptom relief
• Localized action
• Improved patient compliance

Recent advancements focus on biopolymer-based raft systems with enhanced stability and drug loading capacity (Bachhar et al., 2026).

6.7 Delivery of Drugs with Short Half-Life

Drugs with short biological half-lives require frequent dosing, which may reduce patient compliance.

GRDDS enable:

• Sustained drug release
• Reduced dosing frequency
• Improved therapeutic consistency

Examples

• Metformin
• Propranolol

This application significantly enhances patient adherence and treatment outcomes (Kumar et al., 2024).

6.8 Emerging Applications: Biologics and Peptide Delivery

Recent research explores the use of GRDDS for oral delivery of biologics and peptides, which are typically unstable in the gastrointestinal environment.

Approaches

• Mucoadhesive systems for enhanced absorption
• Nanoparticle-loaded GRDDS for protection
• Stimuli-responsive systems for controlled release

Although still in early stages, this represents a promising frontier in oral drug delivery (Grosso et al., 2022; Yang et al., 2024).

6.9 Clinical and Industrial Relevance

Several GRDDS-based formulations have reached the market, demonstrating their clinical utility:

• Floating tablets of ciprofloxacin
• Alginate raft systems for GERD
• Controlled-release formulations for chronic therapy

However, despite extensive research, commercial translation remains limited, highlighting the need for further optimization and clinical validation (Shah et al., 2025).

6.10 Critical Perspective

While GRDDS offer numerous advantages, their application is not universal. Limitations include:

• Dependence on gastric conditions
• Variability in patient physiology
• Limited applicability for drugs unstable in acidic pH

Future developments should focus on hybrid systems, personalized medicine, and integration with advanced technologies to expand the scope of GRDDS applications.

7. CHALLENGES AND LIMITATIONS OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS (GRDDS)

Despite significant advancements in gastro-retentive drug delivery systems (GRDDS), several physiological, technological, and regulatory challenges continue to limit their widespread clinical application. A critical understanding of these limitations is essential for the development of more robust and reliable systems (Tripathi et al., 2019; Shah et al., 2025).

7.1 Variability in Gastric Emptying and Motility

One of the most significant challenges in GRDDS is the high variability in gastric emptying time, which directly affects drug retention and release.

• Gastric motility differs between fasted and fed states
• Inter-individual variability (age, gender, disease conditions)
• Influence of food composition and caloric intake

This variability results in unpredictable gastric residence time (GRT) and inconsistent drug absorption, making it difficult to achieve reproducible therapeutic outcomes (Hua, 2020; Abuhelwa et al., 2016).

7.2 Limited In Vitro–In Vivo Correlation (IVIVC)

A major limitation of GRDDS is the poor correlation between in vitro testing and in vivo performance.

• Standard dissolution tests fail to simulate dynamic gastric conditions
• Variations in pH, motility, and fluid volume are difficult to replicate
• Floating behavior observed in vitro may not translate in vivo

This lack of predictive models complicates formulation optimization and regulatory approval (Mandal et al., 2016).

7.3 Dependence on Gastric Fluid Volume

Many GRDDS, particularly floating systems, rely on sufficient gastric fluid for proper functioning.

• Low fluid volume in fasted state may impair buoyancy
• Insufficient hydration can affect polymer swelling
• Variability in gastric contents impacts performance

As a result, system effectiveness may be compromised under certain physiological conditions (Kumar et al., 2024).

7.4 Drug-Related Limitations

Not all drugs are suitable candidates for GRDDS.

Unsuitable Drugs Include:

• Drugs unstable in acidic pH
• Drugs with high solubility throughout GIT
• Drugs intended for colon-specific delivery

Additionally, drugs with narrow therapeutic index may pose risks if dose dumping occurs (Tripathi et al., 2019).

7.5 Risk of Dose Dumping

Single-unit GRDDS are particularly prone to dose dumping, where rapid release of the entire drug dose occurs due to system failure.

• Polymer matrix rupture
• Premature disintegration
• Mechanical stress in stomach

This can lead to toxicity or adverse effects, especially for potent drugs (Streubel et al., 2006).

7.6 Safety Concerns

Certain GRDDS designs may pose safety risks:

• Expandable systems: Risk of gastric obstruction
• High-density systems: Potential irritation
• Mucoadhesive systems: Possible mucosal damage with prolonged adhesion

Ensuring biocompatibility and safe degradation remains a critical requirement (Mandal et al., 2016).

7.7 Manufacturing and Scale-Up Challenges

Advanced GRDDS often involve complex formulation techniques, leading to challenges in large-scale production:

• Reproducibility issues
• High production cost
• Difficulty in maintaining uniformity (especially in MUDFs)

Emerging technologies like 3D printing also face scalability and regulatory barriers (Alqahtani et al., 2026).

7.8 Regulatory and Clinical Translation Barriers

Despite extensive research, relatively few GRDDS have reached the market due to:

• Lack of standardized evaluation methods
• Insufficient clinical data
• Regulatory uncertainties for novel technologies (AI, nanotechnology)

This highlights the gap between laboratory research and commercial application (Shah et al., 2025).

7.9 Patient Compliance and Variability

Patient-related factors can significantly affect GRDDS performance:

• Dietary habits
• Posture and lifestyle
• Co-administration with other drugs

These factors contribute to variability in therapeutic outcomes, reducing predictability and reliability.

7.10 Critical Perspective

Although GRDDS offer substantial advantages in enhancing drug bioavailability and retention, their effectiveness is often limited by physiological unpredictability and formulation constraints. Current research is increasingly focused on:

• Developing hybrid systems combining multiple retention mechanisms
• Improving in vitro–in vivo predictive models
• Utilizing AI and simulation tools for formulation optimization

Addressing these challenges is essential for translating GRDDS from experimental systems to clinically successful therapies.

8. FUTURE PERSPECTIVES

The field of gastro-retentive drug delivery systems (GRDDS) is rapidly evolving, driven by advances in material science, digital technologies, and precision medicine. Future research is expected to focus on the development of intelligent, patient-centric, and highly adaptable drug delivery platforms capable of overcoming current limitations.

One of the most promising directions is the integration of 3D printing technologies for the fabrication of personalized GRDDS. This approach enables the production of patient-specific dosage forms with tailored drug release profiles, improving therapeutic outcomes and minimizing adverse effects (Alqahtani et al., 2026). Similarly, the application of artificial intelligence (AI) and machine learning (ML) is expected to revolutionize formulation development by enabling predictive modeling, optimization of formulation variables, and reduction in experimental workload (Shah et al., 2025).

Another key area of advancement is the development of multi-functional hybrid systems, which combine multiple retention mechanisms such as floating, mucoadhesion, and swelling. These systems aim to enhance gastric retention reliability and minimize variability associated with physiological conditions. In addition, stimuli-responsive and smart polymers are being extensively explored for their ability to provide site-specific and controlled drug release in response to environmental triggers such as pH, enzymes, and temperature (Yang et al., 2024).

The incorporation of nanotechnology into GRDDS is also expected to expand their applications, particularly in improving the delivery of poorly soluble drugs, peptides, and biologics. Nanocarrier-based GRDDS can enhance drug stability, permeability, and targeting efficiency, opening new possibilities for oral delivery of complex therapeutic agents (Zhang et al., 2025).

Furthermore, future research should focus on improving in vitro–in vivo correlation (IVIVC) through the development of advanced simulation models and biorelevant testing systems. This will facilitate more accurate prediction of clinical performance and accelerate regulatory approval processes.

Despite these advancements, challenges related to scalability, regulatory acceptance, and long-term safety must be addressed. Collaborative efforts between academia, industry, and regulatory bodies will be essential to translate innovative GRDDS technologies into commercially viable and clinically effective products.

9. CONCLUSION

Gastro-retentive drug delivery systems (GRDDS) represent a significant advancement in oral drug delivery, offering effective solutions to overcome limitations associated with conventional dosage forms. By prolonging gastric residence time, GRDDS enhance drug bioavailability, therapeutic efficacy, and patient compliance, particularly for drugs with narrow absorption windows, pH-dependent solubility, and localized gastric action.

This review highlights the fundamental principles, classification, physiological considerations, and recent technological advancements in GRDDS. Traditional approaches such as floating, mucoadhesive, expandable, and high-density systems continue to play a vital role, while emerging technologies including 3D printing, nanotechnology, artificial intelligence, and smart polymers are transforming the field into a more sophisticated and precise drug delivery paradigm.

However, the widespread clinical application of GRDDS remains limited due to challenges such as physiological variability, poor in vitro–in vivo correlation, formulation complexity, and regulatory constraints. Addressing these issues through innovative design strategies and advanced evaluation methods will be critical for future success.

In conclusion, GRDDS hold immense potential as next-generation oral drug delivery systems, and continued research in this field is expected to lead to the development of more efficient, reliable, and patient-specific therapeutic solutions.

REFERENCES

1. Waqar, M.A., Mubarak, N., Khan, A.M., & Khan, R. (2024). Advanced polymers and recent advancements on gastroretentive drug delivery system; a comprehensive review. Journal of Drug Delivery Science and Technology. https://www.tandfonline.com/doi/abs/10.1080/1061186X.2024.2347366
2. Dubey, A., Ovais, M., & Bisen, A.C. (2025). Advancements and challenges in gastroretentive drug delivery systems. Recent Advances in Drug Delivery and Formulation. https://www.benthamdirect.com/content/journals/raddf/10.2174/0126673878342430250414114531
3. Kumar, V., Somkuwar, S., & Singhai, A.K. (2024). A recent update on gastro retentive drug delivery systems. GSC Biological and Pharmaceutical Sciences. https://pdfs.semanticscholar.org/1419/d8ee522825e57bba104f7308e8ba284d3b6d.pdf
4. Shah, K., Singh, D., Agrawal, R., & Garg, A. (2025). Current developments in the delivery of gastro-retentive drugs. AAPS PharmSciTech. https://link.springer.com/article/10.1208/s12249-025-03052-4
5. Zhang, Y., Wang, Y., Lu, Y., Quan, H., & Wang, Y. (2025). Advanced oral drug delivery systems for gastrointestinal targeting. Journal of Nanobiotechnology. https://link.springer.com/article/10.1186/s12951-025-03479-8
6. Mishra, S., Shukla, P., & Chumbhale, D.S. (2025). Exploring the potential of gastro-retentive drug delivery systems. Journal of Pharmaceutical Sciences. https://www.researchgate.net/publication/390731855
7. Patel, V., Vaishnavi, P.N., Thakare, A., & Solanki, H. (2025). Prolonging gastric retention: An in-depth study of GRDDS. Drug Delivery Letters.
8. Kasani, J., Kandula, S.S.L.H., & Katta, N. (2025). Current advances in gastro-retentive drug delivery systems. Journal of Pharma Insights and Research. http://jopir.in/index.php/journals/article/view/545
9. Layek, B. (2024). Xanthan gum-based oral drug delivery systems. International Journal of Molecular Sciences. https://www.mdpi.com/1422-0067/25/18/10143
10. Singh, M., & Das, M.K. (2024). Role of natural polymers in GRDDS. Drug Delivery Letters. https://www.benthamdirect.com/content/journals/ddl/10.2174/0122103031301526241010021238
11. Tripathi, J., Thapa, P., Maharjan, R., & Jeong, S.H. (2019). Current state and future perspectives on gastroretentive drug delivery systems. Pharmaceutics, 11(4), 193. https://www.mdpi.com/1999-4923/11/4/193
12. Hua, S. (2020). Advances in oral drug delivery for regional targeting in the gastrointestinal tract. Frontiers in Pharmacology, 11, 524. https://www.frontiersin.org/articles/10.3389/fphar.2020.00524/full
13. Abuhelwa, A.Y., Foster, D.J.R., & Upton, R.N. (2016). A quantitative review of GI pH variability and drug absorption. AAPS Journal. https://link.springer.com/article/10.1208/s12248-016-9952-8
14. Mandal, U.K., Chatterjee, B., & Senjoti, F.G. (2016). Gastro-retentive drug delivery systems and their in vivo success. Asian Journal of Pharmaceutical Sciences. https://www.sciencedirect.com/science/article/pii/S1818087616300320
15. Rathod, H.J., Mehta, D.P., & Yadav, J.S. (2016). A review on gastroretentive drug delivery systems. https://www.researchgate.net/publication/304744283
16. Streubel, A., Siepmann, J., & Bodmeier, R. (2006). Gastroretentive drug delivery systems. Expert Opinion on Drug Delivery.
17. Wilson, C.G., & O’Mahony, B. (2012). Physiological factors affecting oral drug delivery.
18. Talukder, R., & Fassihi, R. (2004). Gastroretentive delivery systems: A mini review. Drug Development and Industrial Pharmacy.
19. Söderlind, E., & Dressman, J.B. (2010). Physiological factors affecting GI drug absorption.
20. Streubel, A., Siepmann, J., & Bodmeier, R. (2006). Gastroretentive drug delivery systems. Expert Opinion on Drug Delivery.
21. Deshpande, A.A. et al. (1997). Gastroretentive drug delivery systems. Drug Development and Industrial Pharmacy.
22. Singh, B.N., & Kim, K.H. (2000). Floating drug delivery systems. Journal of Controlled Release.
23. Pawar, V.K. et al. (2011). Gastroretentive dosage forms. AAPS PharmSciTech.
24. Zhang, Y., Wang, Y., Lu, Y., Quan, H., & Wang, Y. (2025). Advanced oral drug delivery systems for gastrointestinal targeting. Journal of Nanobiotechnology. https://link.springer.com/article/10.1186/s12951-025-03479-8
25. Dubey, A., Ovais, M., & Bisen, A.C. (2025). Advancements in GRDDS. Recent Advances in Drug Delivery. https://www.benthamdirect.com/content/journals/raddf/10.2174/0126673878342430250414114531
26. Alqahtani, A.A. et al. (2026). 3D printing in gastroretentive systems. Farmacia Journal.
27. Awad, A. et al. (2021). 3D printing in pharmaceutical applications. Advanced Drug Delivery Reviews.
28. Grosso, R. et al. (2022). Smart GRDDS for antibiotic delivery. Pharmaceutics.
29. Bachhar, A. et al. (2026). Biopolymer-based raft systems. Journal of Drug Delivery Science.
30. Patel, V. et al. (2025). GRDDS advancements. Drug Delivery Letters.
31. Shah, K. et al. (2025). AI in pharmaceutical formulation. AAPS PharmSciTech.
32. Rao, S. et al. (2024). Machine learning in drug delivery systems. Pharmaceutical Research.
33. Yang, J. et al. (2024). Stimuli-responsive hydrogels. Composites Part B.
34. Hua, S. (2020). Advances in oral drug delivery. Frontiers in Pharmacology.