Department of Industrial Pharmacy, Bharat Technology, A School of Pharmacy, Uluberia, Howrah- 711316.
Floating drug delivery systems (FDDS) are a promising strategy in the development of gastroprotective dosage forms aimed at enhancing the bioavailability of drugs with a narrow therapeutic window and limited absorption in the gastrointestinal (GI) tract. These systems, which remain buoyant in the stomach, provide a controlled release of the drug, extend gastric retention time, and ensure sustained drug release over extended periods. This review highlights the recent innovations in the formulation of floating tablets, focusing on novel materials, advanced technologies, and the mechanisms governing buoyancy and drug release. Key formulations and techniques include the use of hydrophilic polymers, effervescent systems, super porous hydrogels, and multi-layered tablets, which allow for better control over the buoyancy and release rate. The combination of these approaches has led to enhanced drug stability, improved patient compliance, and better therapeutic outcomes. Additionally, the impact of factors such as pH, density, and formulation excipients on the performance of floating tablets is critically reviewed. Recent advancements also explore the potential of natural polymers, nanotechnology, and 3D printing for designing innovative floating tablet systems. Furthermore, the integration of floating systems with targeted drug delivery for local treatment in the upper GI tract offers exciting prospects. Despite these advancements, challenges such as variable gastric conditions, inter-patient variability, and scaling up for commercial production remain. In conclusion, floating tablets present a promising solution for controlled drug release and localized therapy in the upper GI tract, and ongoing research into formulation strategies and technologies will continue to enhance their clinical application in gastroprotective drug delivery systems.
The oral route is the most effective way to administer drugs for single-dose systems. It is also simple to administer and economical when creating a single-dose controlled release, extended, or sustained release dosage form[1]. Much research has been done to improve patient compliance and prevent the need for repeated drug administration because the drug is highly soluble at acidic pH conditions and less soluble at pH values higher than 7, which results in a lower absorption window from the intestine. The primary benefits of GRDDS include increasing bioavailability and providing site-specific drug delivery for GI disorders.[2] As medication bioavailability rises, dosage repetitions decrease, thereby reducing GI disorders. The GRDDS's incompatibility with drugs that irritate the stomach mucosa is one of its drawbacks as compared to traditional dosing forms. The product substance is intended to remain in the stomach for an unlimited period of time by reaching the upper portion of the gastrointestinal tract. Floating systems, which include low density gas generating systems, and swelling systems are two ways to extend the gastric retention time in the stomach.[3] In these systems, the dosage form floats in the gastric fluid because the component density is lower than the stomach's density. In the high-density system, the dosage form stays in the distal portion of the stomach because its mass is greater than that of the gastric fluid.[4] In the bio adhesive system, the dosage form sticks to the mucosal surface. There are several hypotheses pertaining to these systems. The capillary wetting process in the super porous hydrogel system causes water to be absorbed via the pores, causing the dosage form to enlarge. The polymers in raft producing systems expand and create an in-situ gel layer, which floats above the stomach fluid.[5] Systems swell and unfold in expandable approaches, and this happens through diffusion.
Fig 1. Flowchart showing different approaches for gastroprotective drug delivery systems.
Fig2. Drug absorption (a) Conventional dosage forms (b) Gastroprotective drug delivery system
Details on GRRDS (Gastroretentive Drug Delivery system): A novel type of drug delivery system called a gastroretentive drug delivery system (GRDDS) may stay in the stomach for an extended amount of time, extending the medications gastric residence duration and enhancing their bioavailability.
When the bulk density of these lowdensity systems is lower than that of the gastric fluids, they float in the stomach for an extended amount of time without influencing the rate at which the stomach empties. [6]. The medication is released from the drug deliverysystem gradually and at the appropriate pace when it is floating on the stomach contents. Increased gastric retention time and improved regulation of variations in the plasma drug concentration are the outcomes of this. The following categories relate to floating systems:
1.1 Effervescent Systems[7]:
These dose forms are made in a way that, when encountering the stomach acids in the When sodium bicarbonate, citric acid, and tartaric acid react in the stomach, carbon dioxide gas is produced and trapped in the inflated hydrocolloids. This gives the dose form buoyancy by causing it to float on the stomach contents. These systems might also include liquids that, when heated to body temperature, gasify and evaporate, lowering the specific gravity and making the dose form float.
These effervescent systems have been further classified into different types:
Volatile liquid containing systems.
Gas generating systems.
Volatile liquid containing systems.[8]
These are further classified a
Fig 3. Intra-gastric floating gastrointestinal drug delivery system
Inflatable gastrointestinal drug delivery system: These devices include an inflatable chamber filled with liquid ether, which causes the chamber to expand in the stomach when itgasifier at body temperature. There is a medication reservoir inside this inflatable chamber that is enclosed in a gelatine capsule. Following oral delivery, the capsule dissolves and releases the inflatable and medication reservoir.
Fig 4.Inflatable gastrointestinal delivery system
Intragastric osmotically controlled drug delivery system: It includes an inflatable support in a biodegradable container and a medicine delivery system that is regulated by osmotic pressure
capsule. When the inflatable capsule reaches the stomach, it breaks apart and releases the medication in an osmotically regulated manner. The interior inflatable support creates a flexible, hollow polymeric bag that is inflated by a liquid that gasifier at body temperature. A drug reservoir compartment and an osmotically active compartment make up an osmotic pressure-controlled drug delivery device. The pressure-responsive collapsible bag that encloses the medication reservoir compartment has a delivery opening and is impervious to liquid and vapour. The semi-permeable membrane that encloses the osmotically active salt makes up the osmotically active compartment.
Fig 5.Intragastric osmotically controlled drug delivery system
Gas generating systems:[10]
The creation of gas bubbles in these systems gives them floatability. When carbonates or bicarbonates react with acid—either the stomach's natural acid or co-formulated citric or tartaric acids—carbon dioxide is produced in situ. The gas produced causes the systems to float on the stomach contents and releases the medication.
To make floating capsules, fill them with a solution of sodium bicarbonate and sodium alginate. These float because, when exposed to an acidic environment, carbon dioxide is produced and trapped in the hydrating gel network.
Fig 6. Intact device;
(B) device at the beginning of drug release; (C) device with half drug-polymer compact eroded; and (D) device after complete drug–polymer erosion and evacuation of entrapped carbon dioxide (inflated balloon).
These systems are composed of two layers: an inner effervescent layer that contains tartaric acid and sodium bicarbonate, and the polymeric outer membrane, which can expand. To prevent sodium bicarbonate and tartaric acid from coming into physical touch, the inner layer is further separated into two sub-layers. This pill sinks to the bottom when submerged in buffer solution at 37 °C, and the buffer solution passes through the outer, expandable membrane to reach the effervescent layer. When sodium bicarbonates and tartaric acid mix, carbon dioxide is produced, which causes swollen pills or balloons to develop. The gadget floats because the carbon dioxide produced is trapped inside the delivery mechanism.
Fig 7. Floating pills a) The penetration of water into effervescent layer leads to a CO2 generation and makes the system to float (b) Mechanism of floatation
Non effervescent systems:[11]
Non effervescent drug delivery systems are those which upon swallowing swells via imbibitions of gastric fluids to an extent that it prevents their exit from the stomach. These systems may also be referred to as ‘plug-type systems’ since they have the tendency to remain lodged near the pyloric sphincter.
Fig 8. Floating systems with ion exchange resins
Different types of non-effervescent systems are
Hydro-dynamically balanced systems (HBS)
Micro balloons / hollow microspheres
Alginate beads
Hydro-dynamically balanced systems (HBS):Another term for HBS is "colloidal barrier systems." These systems include medication in addition to the fluid hydrocolloids that gel. The capsule shell dissolves and the mixture swells to form a gelatinous barrier when the capsules containing the drug hydrocolloid mixture come into contact with the gastric fluids. This gives the gastric fluids buoyancy for an extended amount of time because the surface is continuously eroding. This permits water to permeate the interior layers, preserving the dosage form's buoyancy and surface hydration. The pace at which fluid enters the device and the subsequent medication release from the system is regulated by this gel barrier.
Fig 9. Hydro-dynamically balanced systems
Micro balloons / hollow microspheres[12]: The low-density systems known as hollow microspheres or micro balloons have enough buoyancy to stay in the stomach for a long time and float over the contents of the stomach. These systems have a drug-loaded outer polymer shell. The gel forms and polymers hydrate when they come into touch with stomach fluid, creating a colloidal gel barrier that regulates the rate at which fluid enters the device and, in turn, the release of drugs. The gel layer is kept intact by hydrating the nearby hydrocolloid layer while the dosage form's outer surface dissolves. The expanded polymer's trapped air reduces density and provides .The microspheres' buoyancy. Because of their superior floating qualities due to the core hollow area inside the microspheres and their special benefit of being a multiple unit system, they are regarded as one of the most promising buoyant systems.
1.2.3Alginate beads: These are the freeze-dried calcium alginate beads of approximately 2.5 mm diameter prepared by dropping sodium alginate solution into aqueous solution of calcium chloride, causing precipitation of calcium alginate leading to formation of porous system, which helps in floating of the system on the gastric contents. Due to the porous nature these can maintain a floating force for over 12 hours. When compared with solid beads, which gave a short residence time of 1 hour, and these floating beads shows a prolonged residence time of more than 5.5 hours.
Non-Floating drug delivery systems:[13]
These are the drug delivery systems which do not float but remain in the stomach for prolonged period of time. Different mechanism has been used to retain the device in the stomach which includes
Bio adhesive systems
Swelling system
High density systems
Bio adhesive systems: The term bio adhesion is defined as adhesion of the delivery system to biological surface i.e., mucus and/or mucosal surface. Bio adhesive systems adhere to the mucosa of the stomach and remain in intimate contact with the membrane for longer period and hence retains in the stomach for its prolonged release. Bio adhesive polymers are used to formulate these systems.
Fig 10. Bioadhesive drug delivery system
Swelling system: Gastro retentivity of the dosage form can be enhanced by increasing its size above the diameter of the pylorus. Thus, these delivery systems are formulated with swellable polymers which upon entering the stomach causes these polymers to swells to an extent the device cannot pass through the pyloric sphincter leading to the retention of the delivery device in stomach.
Fig 11. Swelling System
High density systems: These are the systems which have the density greater than the density of the gastric fluids as a result these systems sinks to the bottom of the stomach, thus retains in the stomach for prolonged period. These are usually formulated by coating the drug on heavy inert materials like zinc oxide, titanium dioxide, iron powder etc.
Fig 12. High density system
This gastroprotective can greatly increase the bioavailability of therapeutic drugs, particularly those that are processed in the upper GIT. Medication delivery strategy in contrast to the use of non-gastroscopic drug delivery.
Sustained release may lead to a flip-flop pharmacokinetics for medications with a short half-life. It may also allow for less frequent dosage with better patient compliance.[14]
The ability to overcome the challenges of both the gastric retention time (GRT) and the stomach emptying time (GET) gives them an additional edge over their traditional approach.
Gastroretentive medication delivery can create extend and sustain release of pharmaceuticals from dosage forms which avail local treatment in the stomach and small intestine. Hence, they are helpful in treating conditions involving the small intestine and stomach.
The gastroretentive dosage form's regulated, gradual drug administration minimizes or eliminates systemic drug exposure by delivering enough local action at the sick region. This site-specific medication distribution lessens unwanted side effects.[15]
Disadvantages of the formulation of gastroprotective drug delivery system as a floating tablet formulation:
Drugs that are preferentially absorbed in the stomach or upper small intestine (e.g., weakly basic drugs, drugs with narrow absorption windows) benefit from longer gastric retention.
Floating tablets ensure prolonged drug release in this region → better absorption and efficacy.
Formulating the tablet with swellable polymers and gas-generating agents allows slow, steady release of the drug.
Reduces frequency of dosing → improves patient compliance.[19]
By avoiding rapid emptying into the intestine, floating tablets maintain stable plasma concentrationsand minimize side effects due to peak-trough variations.
Useful for drugs intended for local treatment in the stomach(e.g., antibiotics for H. pylori, antacids, misoprostol).
The tablet stays longer in the gastric environment, giving prolonged local activity.[19]
Floating systems release the drug in a controlled manner rather than disintegrating all at once, which is especially important for potent drugs.
Drugs that may cause irritation in the colon (e.g., NSAIDs) can be retained and released in the stomach, reducing adverse effects in the lower intestine.
Drugs like levodopa, furosemide, riboflavin, ciprofloxacin have narrow absorption windows. Floating tablets ensure these drugs remain available for absorption at the right site.[20]
The formulation of gastroprotective drug delivery systems as floating tablets has emerged as an important approach to improve the performance of oral drugs. Floating tablets are designed to remain buoyant in the stomach for prolonged periods, which helps in retaining the dosage form in the gastric region and allows continuous drug release at the site of absorption. This approach is particularly useful for drugs that have narrow absorption windows, are unstable in the intestinal environment, or require local action in the stomach. By providing sustained and controlled release, floating tablets enhance bioavailability, reduce dosing frequency, minimize fluctuations in plasma drug concentration, and improve patient compliance. Additionally, they help in reducing side effects associated with drug release in the lower gastrointestinal tract. Overall, gastroretentive floating tablet formulations represent a promising and patient-friendly technology that ensures better therapeutic outcomes and maximizes the efficiency of oral drug delivery.
REFERENCES
Pradipta Guha, Aveek Datta*, Biplab Debnath, Innovative Approaches in the Formulation of Floating Tablets for Gastroprotective Drug Delivery, Int. J. of Pharm. Sci., 2025, Vol 3, Issue 11, 1517-1527 https://doi.org/10.5281/zenodo.17577730
10.5281/zenodo.17577730
