Herbal-Based Gastro-retentive Floating Tablets: Formulation Strategies, Challenges and Future Perspectives

Abstract

Herbal-based gastroretentive floating tablets represent an emerging approach designed to enhance the therapeutic performance of plant-derived bioactives with poor bioavailability. Many herbal constituents exhibit low aqueous solubility, rapid intestinal degradation, and limited gastric residence time, restricting their clinical efficacy. Floating systems overcome these limitations by maintaining the dosage form in the stomach for an extended period through reduced density or gas-generation mechanisms, allowing prolonged local action and improved absorption. This review summarizes current knowledge on the formulation strategies employed in developing herbal floating tablets, including effervescent and non-effervescent approaches, polymer selection, buoyancy optimization, and release-modifying techniques. Key challenges such as variability in herbal phytochemical composition, stability concerns, regulatory limitations, and scale-up issues are highlighted. The article also outlines potential future perspectives, emphasizing the need for standardized herbal extracts, advanced polymeric systems, in vivo–predictive evaluation models, and patient-centric dosage design. The review aims to provide a comprehensive understanding of the scientific basis, technological developments, and opportunities in the field of herbal based gastroretentive floating drug delivery systems.

Keywords

Herbal-based gastroretentive systems, Floating tablets, Bioavailability enhancement ,Polymer selection, Buoyancy optimization

Introduction

3. EXCIPIENTS USED IN HERBAL-BASED GASTRORETENTIVE FLOATING TABLETS

In addition to polymers, various excipients are critical for the successful formulation of herbal floating tablets. These excipients aid in buoyancy, tablet formation, stability, drug release modulation, and overall patient compliance.

1. Polymers (As Discussed Earlier)¹⁷

Provide gel-forming, swelling, and controlled-release properties.

Examples: HPMC, Carbopol, Guar gum, Xanthan gum, Pectin, Chitosan.

2. Gas-Generating Agents

Sodium Bicarbonate: Reacts with gastric acid to release CO?, which gets trapped in the polymer matrix and provides buoyancy.^17-18

Citric Acid or Tartaric Acid: Acidic component that reacts with sodium bicarbonate to facilitate rapid gas generation.

The amount and ratio of these agents are critical to balance floating lag time and tablet integrity.¹⁹

3. Fillers / Diluents

Used to increase bulk and ensure tablet size suitable for gastric retention.

Must be compatible with herbal actives and not interfere with floating.¹⁹

Common fillers:

Microcrystalline Cellulose (MCC): Provides compressibility and improves tablet hardness.

Lactose: Water-soluble filler but limited use with moisture-sensitive herbal extracts. Dicalcium Phosphate: Insoluble filler for controlled release and tablet strength.

4. Binders

Ensure adequate cohesiveness of tablet ingredients.

Examples:

Polyvinylpyrrolidone (PVP): Enhances tablet integrity and sometimes improves solubility of herbal compounds.

Starch: Natural binder commonly used in herbal formulations.²⁰

5. Lubricants and Glidants

Facilitate smooth tablet compression and ejection.

Examples:

Magnesium Stearate: Most common lubricant; use in minimal amounts to avoid interfering with tablet wettability.^21,22

Talc: Acts as a glidant to improve powder flow during manufacturing.

6. Disintegrants (Optional)

Generally minimized or avoided in floating tablets to maintain integrity and buoyancy.

If used, natural disintegrants like plantago ovata husk may be preferred to support swelling without rapid disintegration.²²

7. Solubility Enhancers

Enhance dissolution of poorly soluble herbal actives.

Examples:

Surfactants (e.g., Sodium Lauryl Sulfate): Improves wettability and solubilization. Cyclodextrins: Form inclusion complexes to increase aqueous solubility.²³

8. Stabilizers and Antioxidants

Protect sensitive herbal phytoconstituents from oxidation or degradation.

Examples:

Ascorbic Acid (Vitamin C)

Butylated Hydroxyanisole (BHA) or Butylated Hydroxytoluene (BHT) (use with caution in herbal products).²⁴

4. STEP-WISE MANUFACTURING METHOD OF HERBAL GASTRORETENTIVE FLOATING TABLETS

1. 1. Method 1: Direct Compression

1. Weighing and Sieving

Accurately weigh the herbal extract, polymers, gas-generating agents, fillers, and other excipients. Pass all powders through a suitable sieve (e.g., #60) to ensure uniform particle size.²⁵

2. Mixing / Blending

Mix the herbal extract with polymers (e.g., HPMC, carbopol), fillers (e.g., microcrystalline cellulose), and other excipients (like sodium bicarbonate and citric acid) in a suitable blender (e.g., V-blender or planetary mixer).

Blend for sufficient time (10–15 minutes) to ensure uniform distribution.²⁶

3. Lubrication

Add lubricants such as magnesium stearate and glidants like talc to the blend.

Mix gently for 2–3 minutes to avoid over-lubrication, which can affect tablet hardness and buoyancy.^27-29

4. Compression

Compress the blend into tablets using a rotary tablet press or single-punch press with appropriate tooling. Optimize compression force to ensure sufficient hardness without compromising porosity needed for floating.³⁰

5. Evaluation

Test tablets for weight variation, hardness, friability, floating lag time, total floating time, and drug release profile.

Adjust formulation or compression parameters if required.³¹

4.2 Method 2: Wet Granulation

1. Weighing and Sieving

Weigh all herbal extract, polymers, fillers, and excipients accurately. Pass powders through a suitable sieve for uniformity.^31,32

2. Preparation of Binder Solution

Prepare a binder solution (e.g., PVP in water or isopropyl alcohol) at appropriate concentration (2–5% w/v).³³

3. Mixing and Granulation

Blend dry powders (herbal extract, polymers, fillers, gas-generating agents) in a blender. Slowly add binder solution while mixing to form a wet mass with suitable consistency.³⁵

4. Screening of Wet Mass

Pass the wet mass through a sieve (e.g., #12) to form granules.³⁶

5. Drying

Dry the granules in a tray dryer or fluidized bed dryer at controlled temperature (40–50°C) to avoid degradation of herbal actives.³⁶

6. Sizing of Granules

Pass dried granules through a sieve (e.g., #18) to break lumps and obtain uniform size.³⁷

7. Blending with Lubricants

Add lubricants (magnesium stearate) and glidants (talc) to the dried granules and blend gently.³⁸

8. Compression

Compress the granules into tablets using a tablet press under optimized compression force.³⁹

9. Evaluation

Assess physical properties, buoyancy parameters, and in vitro drug release.⁴⁰

5. EVALUATION PARAMETERS FOR HERBAL-BASED GASTRORETENTIVE FLOATING TABLETS

Evaluation of gastroretentive floating tablets is critical to ensure their physical integrity, buoyancy behavior, drug release characteristics, and stability. Each parameter provides insights into the formulation’s performance in the gastric environment.

1. 1. Physical Evaluation

a. Weight Variation

This test checks the uniformity of weight across tablets from a batch. Tablets are individually weighed, and the average weight is calculated. The deviation of each tablet’s weight from the average should be within pharmacopeial limits. Uniform weight ensures consistent dosing of the herbal active, which is crucial for therapeutic efficacy.⁴¹

b. Hardness (Tablet Crushing Strength)

Measured using a hardness tester, it determines the force required to break a tablet diametrically. Adequate hardness is essential to withstand handling, packaging, and transportation stresses without fracturing. However, excessive hardness may affect tablet disintegration and drug release.⁴²

 c. Friability

This test assesses the tablet’s resistance to abrasion and mechanical shocks. Tablets are rotated in a friabilator, and weight loss is calculated. A friability value of less than 1% is generally acceptable, indicating good mechanical strength.^43,44

d. Thickness and Diameter

Uniformity in thickness and diameter ensures consistent tablet size, which affects packaging and patient compliance.⁴⁵

e. Content Uniformity

Determines the uniform distribution of the herbal active in each tablet. It is performed by assaying multiple tablets for active content, ensuring each dose delivers the intended therapeutic amount.⁴⁶

1. 2. Buoyancy ⁴⁷

a. Floating Lag Time (FLT)

Floating lag time is the time interval between tablet immersion in simulated gastric fluid (SGF) and its rise to the surface. Shorter FLT is desirable to ensure the tablet promptly begins floating upon reaching the stomach, avoiding premature gastric emptying.

2. Total Floating Time (TFT)

Total floating time measures the duration for which the tablet remains buoyant on the gastric fluid surface. Prolonged TFT (usually >8 hours) is critical for sustained gastric retention and controlled drug release.

5.3 Swelling Index

This parameter evaluates the extent of swelling of the tablet when in contact with SGF. The tablet is weighed before and after immersion at specified intervals, and swelling is calculated as a percentage increase in weight. Swelling is mainly due to polymer hydration and gel formation, which helps maintain buoyancy and modulate drug release.⁴⁸

5.4 In Vitro Drug Release Studies

Performed using dissolution apparatus (USP Type II paddle method) in SGF (pH 1.2), this test monitors the rate and extent of herbal active release over time. Sampling at predetermined intervals provides a drug release profile. Data are analyzed to determine release kinetics (zero-order, first-order, Higuchi model, Korsmeyer-Peppas), which indicate whether release is controlled by diffusion, erosion, or a combination.^48-49

5.5 Stability Studies

Herbal floating tablets are subjected to accelerated stability testing as per ICH guidelines, usually at 40°C ± 2°C and 75% ± 5% relative humidity for 3–6 months. Tablets are evaluated periodically for physical appearance, hardness, floating behavior, drug content, and dissolution profile. Stability data ensure the formulation maintains efficacy and safety during its shelf life.⁵⁰

5.6 Additional Evaluation

a. Mucoadhesion Test (If Applicable)

Some formulations incorporate mucoadhesive polymers to enhance gastric retention via adhesion to the mucosal lining. The strength of adhesion can be assessed using texture analyzers or ex vivo mucosal tissues.⁴⁸

b. Scanning Electron Microscopy (SEM)

SEM provides detailed images of tablet surface morphology, revealing porosity and structural integrity related to buoyancy and drug release.⁴⁹

c. Fourier Transform Infrared Spectroscopy (FTIR)

Used to detect any chemical interaction or incompatibility between herbal actives and excipients, ensuring formulation stability.⁵⁰

6. CHALLENGES IN FORMULATING HERBAL-BASED GASTRORETENTIVE FLOATING TABLETS 

Formulating gastroretentive floating tablets using herbal actives presents unique challenges due to the complex nature of herbal extracts and the demanding requirements of gastroretentive systems. Understanding these challenges is essential for developing effective and stable formulations.

1. Complexity and Variability of Herbal Extracts

Herbal extracts contain multiple bioactive compounds with varying physicochemical properties, which can affect solubility, stability, and release profiles. Batch-to-batch variability due to differences in plant sources, extraction methods, and storage conditions complicates standardization.^47-49

2. Stability Issues

Many herbal constituents are sensitive to heat, moisture, and gastric pH, making them prone to degradation during manufacturing, storage, and gastric transit. Protecting these compounds while maintaining floating properties requires careful selection of excipients and processing conditions.⁵¹

3. Poor Water Solubility and Bioavailability

Several herbal actives exhibit poor aqueous solubility and low bioavailability. Achieving adequate dissolution and absorption during prolonged gastric retention demands advanced formulation techniques such as solid dispersions, complexation, or use of solubilizers.⁵¹

4. Controlling Floating Behavior

Balancing buoyancy with mechanical strength is challenging. Excessive gas generation may cause rapid disintegration, whereas insufficient gas leads to poor floatation. Optimizing gas-generating agents and polymer matrix composition is critical.^{49, 50}

5. Scale-Up and Manufacturing Reproducibility

Translating laboratory-scale formulations to commercial production while maintaining consistent quality is difficult, especially with herbal materials that may vary in characteristics. Process parameters must be tightly controlled.⁵¹

6. Regulatory and Standardization Challenges

Herbal formulations require stringent quality control, standardization of active markers, and thorough documentation to meet regulatory requirements. Lack of standardized herbal raw materials adds to complexity.⁵¹

7. Patient Acceptability

Taste, size, and dosing frequency affect patient compliance. Herbal extracts often have strong flavors or odors, requiring taste-masking strategies.⁵⁰

7. FUTURE PROSPECTS OF HERBAL-BASED GASTRORETENTIVE FLOATING TABLETS

The development of herbal-based gastroretentive floating tablets holds significant promise for improving therapeutic efficacy and patient compliance in herbal drug delivery. Advancements in formulation technology and scientific understanding are paving the way for innovative solutions.

1. Advanced Polymer Technologies

New biocompatible and biodegradable polymers with enhanced swelling, mucoadhesive, and controlledrelease properties are being explored to improve gastric retention and targeted delivery of herbal actives.⁵¹

2. Nanotechnology Integration

Incorporating herbal extracts into nanoparticles, nanomicelles, or nanoemulsions can enhance solubility, stability, and bioavailability. Combining these with floating systems can synergistically optimize drug release and absorption.⁵²

3. Multifunctional Gastroretentive Systems

Development of floating tablets with combined mechanisms, such as floating plus mucoadhesion or floating with expandable components, to further prolong gastric residence time and improve site-specific action.^{52, 53}

4. Standardization and Quality Control

Improved analytical methods for standardizing herbal extracts and monitoring active constituents will enhance reproducibility and regulatory acceptance of herbal gastroretentive formulations.⁵³

5. Personalized Herbal Therapy

Advances in pharmacogenomics and personalized medicine may enable tailoring gastroretentive herbal tablets to individual patient needs for better efficacy and reduced side effects.⁵³

6. Green and Sustainable Formulation Approaches

Use of eco-friendly excipients, solvent-free manufacturing processes, and sustainable sourcing of herbal materials align with global trends towards green pharmaceutical manufacturing.^{54, 55}

7. Clinical Validation

More clinical trials evaluating the safety, efficacy, and pharmacokinetics of herbal gastroretentive floating tablets will strengthen their acceptance and adoption in mainstream medicine.⁵⁵

This evolving field offers exciting opportunities to harness the therapeutic potential of herbs in a more effective and patient-friendly manner through innovative gastroretentive drug delivery systems.

CONCLUSION

Herbal-based gastroretentive floating tablets represent a promising advancement in the field of drug delivery, combining the benefits of prolonged gastric retention with the therapeutic potential of herbal medicines. The unique ability of floating tablets to remain buoyant in the stomach enhances the bioavailability and efficacy of herbal actives, especially those with narrow absorption windows or instability in the intestinal environment.

Despite the challenges posed by the complexity and variability of herbal extracts, formulation strategies involving natural and synthetic polymers, gas-generating agents, and advanced manufacturing techniques have demonstrated successful development of stable, effective gastroretentive systems. Rigorous evaluation methods ensure these formulations meet the necessary quality standards for clinical use.

Future prospects such as integration of nanotechnology, multifunctional delivery systems, and personalized herbal therapy hold significant potential to further improve the safety, efficacy, and patient compliance of herbal gastroretentive tablets.

Overall, with continued research, standardization, and clinical validation, herbal-based gastroretentive floating tablets can become a vital tool in optimizing herbal drug therapy and expanding their acceptance in modern pharmaceutics.

ACKNOWLEDGEMENT

The authors thankful to KCT’S Krishna College of Pharmacy, Karad and  Krishna Vishwa Vidyapeeth Deemed to be University Karad for providing necessary assistance for conducting this research work.

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