A Comprehensive Review on Gastro Retentive Drug Delivery System

Mansuri Jahid*, Rehan Deshmukh, Khan Ramiz.V, Sayyed Anas Ali     

1. JIIU’s Ali Allana College of Pharmacy Akkalkuwa, Dist-Nandurbar -425415, Maharashtra, India

 

*Correspondence: mansurijahid707@gmail.com; Tel.: (+91 9518983892)

Article Information		Abstract
Review Article Received: 23/10/2024 Accepted: 28/10/2024 Published:08/11/2024   Keywords GRDDS, Type of GRDDS, Factors Affecting In GRDDS, Approaches, Effervescent System, Non-Effervescent System, Polymers,		The Gastroretentive Drug Delivery System (GRDDS) is an advanced approach for enhancing the oral delivery of drugs by prolonging their retention in the stomach. By extending the stomach residence duration, this approach improves therapeutic efficacy and bioavailability while addressing issues including site-specific drug absorption and restricted bioavailability. Dosage forms are kept in the stomach using a variety of methods, including as floating and non-floating systems, which maximize retention by taking into account characteristics like density, shape, and polymer kinds. Additionally, both synthetic and natural polymers are used in the GRDDS, which affects the therapeutic results and release patterns. GRDDS has drawbacks, such as issues with formulation and appropriateness for specific medications, despite its advantages, which include increased bioavailability and decreased drug waste. These technologies are still being developed in order to get beyond physiological obstacles and enhance the results of oral medication delivery.

 

INTRODUCTION

The most popular method of medicine delivery is oral because it is simple to utilize. Oral medication absorption usually takes place in the stomach and intestines. The Gastro Residence Time (GRT) factor contributes to imperfect absorption in the stomach. The medication does not remain in the stomach due to the existence of gastric emptying time that’s why it is necessary to increase GRT. The more time a medicine spends in the stomach, the more absorption takes place and raising the drug's bioavailability. Consequently, a drug delivery system such as the gastroretentive drug delivery system (GRDDS) that can prolong the duration of interaction with the stomach is required. GRDDS formulations have been the subject of numerous studies. These have included formulations of nifedipine and nilotinib to boost bioavailability, antibiotics to boost drug efficacy against H. pylori treatment, ofloxacin as a delayed release drug delivery system, increasing the solubility of verapamil medications, furosemide, propranolol, and other medications.⁽¹⁾ Oral drug delivery systems suffer several challenges, including limited bioavailability because of the heterogeneity of the gastrointestinal tract, commensal flora's pH, the dosage form's GI retention duration, surface area, and enzymatic activity. The gastrointestinal tract (GIT) can present challenges for conventional drug delivery methods, including low dosage effectiveness, frequent dose requirements, and partial drug release. Thus, the development of GRDDS may result from the lack of ability conventional drug delivery methods to keep medications in the stomach. These systems have a number of advantages, including the capacity to give targeted medication distribution in the stomach, longer gastric residence time (GRT) of dose forms in the stomach—up to several hours—and improved drug absorption, which increases therapeutic efficacy. ⁽²⁾

The oral route of drug administration is the most popular and efficient way to distribute drugs.⁽³⁾  The oral drug delivery system is the most favored and traditional method of drug delivery since it is simple to administer, promotes patient compliance, and offers formulation accessibility. The systemic effects that arise from medication absorption through the gastrointestinal tract are the target of oral dose forms. ⁽⁴⁾ One of the main issues with conventional delivery is that it is not site-specific. Certain medications can only be absorbed at a particular locationThey need to be released at an accurate place or in a way that ensures the maximum quantity of medicine reaches the designated location. ⁽⁵⁾

Gastro retentive drug delivery system refers to the controlled release drug delivery method that can be kept in the stomach.⁽⁶⁾  They may be helpful in maximizing the "absorption window" for oral controlled drug delivery by continuously delivering the medication before the window for a longer period of time, assuring maximum bioavailability. Both in fed and fasting conditions, gastric emptying takes place. Still, there are differences in the motility patterns between the two states. Orally administered controlled release dosage forms can be exposed to two difficulties, according to gastric emptying studies: short stomach residence time and unpredictable gastric emptying rate. ⁽⁷⁾

Physiology of stomach :⁽⁸⁾

The stomach is divided anatomically into three regions: the body, the antrum (pylorus), and the fundus. While the antrum is the primary location for mixing motions and functions as a pump for stomach emptying by thrusting activities, the proximal portion, composed of the fundus and body, serves as a reservoir for undigested materials. Both whether a person is fed or fasted, gastric emptying occurs.  An electrical sequence known as the interdigestive myloelectric cycle, or migrating myoelectric cycle (MMC), occurs during the fasting state and cycles through the stomach and intestine every two to three hours.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                            Figure. Anatomical structure²

Risk Factors In the Delivery of Gastroretentive Medication: ⁽⁹⁾

·         Minimal for acid-sensitive drugs. Limited for drugs that are better absorbed in the lower portion of the digestive system.

·         Concerns with the intended dumping and outcome.

·         A number of variables, such as meal presence, pH, and stomach motility, influence gastric retention. It is consequently necessary for the dose form to be able to withstand stomach peristalsis.

·         In vitro and in vivo connections are not good.

·         The cost of phrasing is higher.

·         With toxic, poisonous, or hypersensitivity effects, withdrawal of the medication can be challenging.

Factors affecting gastric retention time of the dosage form: (8)

1) Density:

The density of the dosage form should be less than that of the stomach's contents (1.04g/ml).

2) Size:

A dosage form that is larger than 7.5 mm in diameter stays in the stomach longer than one that is 9.9 mm in diameter.

3) The Shape of the dosage form:

The tetrahedron formulation with one or more units remained in the stomach for a longer period of time when compared to other devices of the same size. Multiple unit formulations show a more consistent release profile and lack of degradation due to unit failure when compared to single unit dose forms. They also offer a higher margin of safety against dosage form failure and coadministration of units with dissimilar release profiles or containing incompatible chemicals.

Non-floating dose forms have extremely varying mean stomach residence periods that are largely depending on their size (larger, medium, or small). Larger dose forms typically have longer gastric retention times because their size prevents them from passing through the pyloric antrum and into the intestine as quickly. ⁽¹⁾

4) Fed or unfed state:

Every one to two hours, there are intense bursts of motar activity that define the stomach                motility during a fast. When the unit is in the fast state, the stomach is cleared of undigested material, which causes the MMC to be delayed and the GRT to be prolonged. In other words, the unit's GRT might be relatively short if the formulation and MMC times are the same.

5) Nature of meal:

When the stomach is fed indigestible polymers or fatty acids, the motility pattern of the stomach changes to a fed state, which prolongs the release of medication and slows down gastric emptying.

6) Caloric content:

GRT can be increased by 4-10 with a meal that is high in protein and fat.

7) Frequency of feed:

The GRT can increase by more than 400 minutes when numerous meals are supplied as opposed to a single meal because of the low frequency of MMC.

8) Gender:

Males have a mean ambulatory GRT of 3.4 hours, which is smaller than that of females of the same age and race (4.6 hours), regardless of height, weight, or body surface. In general, this indicates that women empty their stomachs more slowly than men do.

9) Age:

GRTs are notably longer in those over 70 years old.

10)  Concomitant drug administration:

GRT can be extended by opiates such as codeine and anticholinergic medications such as atropine and propetheline.

Advantages Of GRDDS :^(10,8)

·         Its improves bioavailability.

·         It can reduces drug waste.

·         Enhances the solubility of medications that are less soluble in the high pH environment of the small intestine.

·         It also enhanced therapeutic effectiveness

·         It can be used to overcome the difficult of the gastric retention time (GRT) as well as the gastric emptying time (GET).

·         Medication dose forms that are gastroretentive reduce the variation in drug effects and concentrations.

·         Drug efficiency can be increased by using gastroretentive drug delivery, which can reduce the body's counteractivity.

·         It enhances the pharmacological effects and improves the chemical outcomes.

Disadvantages Of GRDDS :^(11,8)

·         Unsuitable for drugs those are unstable inacidic environment.

·         Unsuitable for drugs with limited acid solubility. E.g. Phenytoin.

·         Medication that, when released slowly, irritates the stomach or creates sores.

·         Drugs that absorb equally well through GIT.

·         Floating drug delivery systems require high fluid level in stomach to float and work effectively.

·         GRDDS is fed into the system after the meal as time of stay in stomach depends on digestive state.

·         The patient must be positioned upright for the medication to stay in the stomach.

·         The Hydrogel based swelling system takes longer time to swell after administration.

·         Upon multiple administrations, size increasing drug delivery systems pose the threat to life owing to possible hazard of permanent retention in stomach.

Different Gastroretentive approaches :

Different approaches have been pursued to increase the retention of oral dosage forms in the stomach. Some are formulated as a single component whereas others are formulated as a multi-component dosage forms. GRDDS can be broadly categorized into floating and non-floating system.⁽¹²⁾

(I)         FLOATING drug delivery SYSTEM :

In contrast to the high-density drug delivery system, Floating systems stay in the stomach for extended periods of time without influencing the gastric contents because their density is lower than that of the stomach's contents. Floating drug delivery systems are also known as low density system. ⁽¹²⁾

Classification of floating drug delivery system: ⁽⁴⁾

(A) Effervescent system:

1.   Gas generating system

2.   Inflatable liquid-containing system

(B)   Non- effervescent system:

1. Colloidal gel barrier systems

2. Microporous Compartment System

3. Alginate beads

4. Raft forming systems

A.   Effervescent system:

These are matrix-type systems made using effervescent substances like sodium bicarbonate, tartaric acid and swellable polymers like methylcellulose. The matrices are fabricated so that upon coming in the stomach, CO2 is released by the acidic nature of the gastric contents and is entrapped in the jellified hydrocolloid. This keeps the dose form buoyant and causes it to move upward. The dose form floats on the chyme due to a decrease in specific gravity.

1.                 Gas generating system:

The primary mechanism in this system is the reaction between sodium bicarbonate, citric acid, and tartaric acid, which produces CO2 gas. The system's density is lowered by the gas generated, enabling it to float on stomach contents. CO2 is produced by salts and citric/tartaric acid, which is trapped in the system's jellified hydrocolloid layer, which lowers its specific gravity and causes it to float over the chime. Essentially, this method uses a multi-layered continuous release tablet as its seed. Tartaric acid and sodium bicarbonate are present in the effervescent inner layer. The outermost layer consists of a swellable membrane layer composed of PVA shellac and other components.⁽¹³⁾

 

                                                          Fig. Effervescent drug delivery system²

2.                 Inflatable liquid-containing system:

These feature an inflatable chamber that fills with a liquid (cyclopentane or ether) that gasifies at body temperature and causes the chamber to expand in the stomach. These are buoyant structures using a hollow deformable element that is regulated by osmoticism. The medication is kept in the first chamber of the system, while the volatile system is kept in the second. medication delivery by floating that isn't effervescent.⁽¹³⁾

A.  Non-effervescent system:

The mechanism underlying the non-effervescent FDDS is polymer swelling or bioadhesion to the GI tract mucosal layer. The medication expands after being swallowed and imbibition of gastric juice prevents it from leaving the stomach. The medicine is mostly combined with gel, which causes it to retain its shape and swell when it comes into touch with stomach fluid. These systems are sometimes called "plug-type systems" because of their propensity to become lodged in the vicinity of the pyloric sphincter. The most widely utilized excipients in non-effervescent floating drug delivery systems include matrix-forming polymers like polyacrylate, polymethacrylate, and polycarbonate, gel-forming or highly swellable cellulose type hydrocolloids, and polysaccharides. ⁽¹⁴⁾

MECHANISM OF FLOATING SYSTEM : (14)

 

 

FDDS has a bulk density less than gastric fluids so that they remain buoyant in the stomach without affecting the gastric emptying rate for a prolonged period of time.

F=F buoyancy-F gravity

= (Df-Ds) gv Where,

F=total vertical force, Df=fluid density, Ds=object density, V=volume,

g=acceleration due to gravity.

Colloidal gel barrier systems :

The first hydrodynamically balanced system (HBS) was invented by Sheth and Tossounian in 1975. In order to keep the medication buoyant in the stomach contents, this treatment uses a pharmaceutical that contains gel-forming hydrocolloids. This system is made up of tablets or capsules that have a high concentration of one or more matrix-forming polymers such polycarbophil, polyacrylates, and polystyrene, and gel-forming, highly swellable cellulose hydrocolloids like HEC, HPMC, NaCMC, and Polysacchacarides. When the system's hydrocolloid comes into contact with gastric fluid, it hydrates and forms a colloidal gel barrier that surrounds the gel surface. The air retained by the expanded polymer has a density less than unity, which makes this dosage form buoyant. ⁽¹³⁾

Microporous Compartment System:

The principle behind this approach is to enclose a drug reservoir within a microporous chamber with apertures positioned on both the upper and lower surfaces. To ensure that no undissolved medication comes into contact with the gastric mucosal surface, the drug reservoir compartment's peripheral walls are sealed completely. The delivery system floats above the contents of the stomach because trapped air is present in the flotation chamber. The medication is dissolved by gastric fluid that enters through the apertures and constantly transports the dissolved drug into the intestine for absorption.⁽¹³⁾

Alginate beads:

Calcium alginate that has been freeze-dried has been utilized to make floating dosage forms containing numerous units. Calcium alginate precipitates when a sodium alginate solution is dropped into an aqueous solution of calcium chloride, resulting in spherical beads with a diameter of roughly 2.5 mm. The beads are then snapped apart and frozen in liquid nitrogen before being freeze dried at -40° for 24 hours, resulting in a porous structure with up to 12 hours of floating force .⁽¹³⁾

Raft forming systems:

The creation of a viscous cohesive gel in contact with stomach contents is the main mechanism underlying the production of rafts, where each segment of liquid expands to form a continuous layer known as a raft. Gelation begins with the formation of double helical junction zones, which are followed by the aggregation of double helical segments, which are then cationcomplexed and hydrogen bonded to form three-dimensional networks. The raft floats and functions as a barrier to stop stomach contents like HCl and enzymes from refluxing into the oesophagus due to the buoyancy brought on by CO2 generation.⁽¹³⁾

Non-Floating Drug Delivery Systems :

Mucoadhesive or Bioadhesive Systems:⁽¹⁵⁾

The mucoadhesive system was first introduced by Park and Robinson. This system is intricate and has multiple working systems. Mucoadhesive systems have the ability to adhere to the gastric mucous membrane, hence extending the GRT. Bioadhesive polymers are used in this technique. These polymers have the ability to stick to the stomach's epithelial surface. By improving the affinity and length of contact between the gastroretentive drug delivery mechanism, gastric retention is prolonged. The negatively charged mucosal surface and positively charged polymer may interact to facilitate the bioadhesive process. Among the excipients that have been employed are gliadin, polycarbophil, lectins, chitosan, and carbopol. Owing to the creation of disulphide bonds both within and across chains, these conjugates can significantly improve cohesive characteristics, leading to an almost zero order   release of the model drug.⁽²⁾ Utilized polymers in the formulation can adhere to the mucosal membrane through receptor-mediated, bonding, or hydration mechanisms.

·         Hydration Mediated Adhesion: Hydrophilic polymers become clingy and mucoadhesive upon hydration.

·         Bonding Mediated Adhesion: May involve mechanical or chemical bonding.

·         Receptor Mediated Adhesion:    Takes place between certain polymers and specific receptors that are defined on gastric cells.

Oral dosage forms attach themselves to the mucin or gastric epithelial cell surface, which improves the closeness and duration of the drug's contact with the biological membrane. As a result, the period of gastric residency will increase. Developing floating systems combined with mucoadhesion properties is one method to get over some of the system's obstacles. This will enhance the dose form's adhesion to the stomach wall's mucous lining. Studies find this system appealing because of its effective responses achieved by formulations. It is among the methods that FDDS is focusing on the most.

 

Figeur. GRDDS based on (a) expandable systems and (b) superporous hydrogel systems⁽²⁾

High Density System:

High-density systems are made to sink to the bottom of the stomach because their density is higher than that of gastric fluids. Usually made of heavier materials or denser polymers, these systems,Prolonged interaction between the drug delivery system and the gastrointestinal mucosa is made possible by the high-density characteristic (16).When the pellets' density is at least 1.5 g/ml, they have a longer stomach residence duration when fed state and fasted state.⁽¹⁵⁾

               

Figure. GRDDS based on (a) low-density systems and (b) high-density systems.⁽²⁾

Swelling system:

Swelling systems are made to absorb stomach fluid and swell to a large size. They are sometimes referred to as superporous hydrogels or swelling prevents the system. The system is unable to cross the pyloric sphincter and enter the small intestine as a result of this enlargement. The drug is released as the system swells and gradually erodes.⁽¹⁶⁾

 

                              Figure. (a)Exapandable system and (b) superporous hydrogel systems⁽²⁾

 

Exapandable system :

Expandable drug delivery systems are made to increase in volume or form in order to have a longer GRT. It was originally used for veterinary purposes, but later on, human applications were added. Three general design considerations must be made for the system to work properly: reduced in size to facilitate evacuation after full medication release, inflated in the stomach to obstruct passage through the pyloric sphincter, and small for simple oral consumption. Because this device can block the pyloric sphincter, it is often referred to as a "plug type system." Similar to swelling systems, expandable systems enlarge when in contact with stomach contents. The medication can be supplied gradually over time thanks to expandable systems, which are specifically designed to expand in a controlled manner. These systems could be made up of a variety of hydrated polymer-based materials.⁽¹⁶⁾

The various expandable and superporous system in GRDDS generally , consists of drug and swellable polymer and high swellable polymer respectively. ⁽¹⁶⁾

Polymers used in gastric retention systems:⁽¹⁷⁾

Mainly two types of polymers are used in formulation, it may be naturally occurring or may be synthetic or may be semisynthetic. A natural polymers has a some advantages such as :

Natural polymers:

Advantages of natural polymers :

·         It can be low cost.

·         Have a biocompatible .

·         Its easily available the means its locally availability.

·         Alos its biodegradable.

·         It can be non- toxic.

·         These polymers are environment friendly.

·         Increased viscosity due to rapid swelling.

·         Also its non-irritating.

Natural Polymers have some disadvantages like:

·         Extraction process very complicated and high cost

·         High degree of variability

·         Uncontrolled rate of hydration

·         Microbial contamination

·         Reduced viscosity on storage.

There are so many type of natural polymers such as :

1)      Chitosan:

Chitosan is a naturally occurring swellable polymer that is an N-deacetylate derivative of chitin.Chitosan is a biocompatible, non-toxic polymer that degrades naturally. It can be applied in two ways to oral extended release tablets: directly compressing the material or granulating it. It has no smell, is soluble in water but partially insoluble in 95% ethanol, and has creamy or white flakes or powder. It functions as a disintegrant, coating agent, mucoadhesive, tablet binder, and viscosity enhancer.Chitosan has a significant impact on the transport of drugs to the stomach, intestines, and colon. A prolonged release behavior is achieved by chitosan at a concentration equal to 50% of the tablet weight.

2)      Guar gum:

Cymopsis tetragonolobus seeds are the natural source of guar gum, a naturally occurring non-ionic polysaccharide that is a member of the Leguminosae family. In solid dosage forms, it serves as a disintegrant, binder, and polymer.It dissolves in water but not in inorganic solvents. It is an odorless, pale yellow powder with no taste. It is primarily made up of high molecular weight polysaccharides (50000–8000000) that are mannose and galactomannans. The presence of particles, PH, and temperature all affect gum's viscosity.

3)      Xanthan gum:

It is a well-known edible gum made of glucose, mannose, and glucuronic acid that is a natural biopolymer. It can be employed as an emulsifying, suspending, thickening, stabilizing, gelling, and raising viscosity agent. Zero order drug release kinetics are a benefit of Xanthan gum over HPMC drug release, which has been demonstrated to occur more quickly at greater electrolyte concentrations (potassium or sodium chloride). When included in tablets, xanthan gum makes an excellent choice for a controlled release formulation. Its natural origin, biocompatibility, safety, and affordability make it a valuable ingredient in pharmaceutical products.

4)      Sodium alginate:

Soil bacteria and brown seaweeds synthesize alginate, a polysaccharide. It is non-immunogenic, PH sensitive, biocompatible, and bioadhesive. Many biological activities of sodium alginate include immunological modulatory, anti-tumor, anti-coagulant, and vascular endothelial growth factor activities.

5)      Carrageenan:

It is frequently employed as a thickening and bulking agent. These polysaccharides, which form gels, are taken from species of red sea weeds like Euchema and Chondrus crispus. Its toughness and viscoelastic nature made it suitable for use as an excipient ingredient in tablets during granulation and compression.

6)      Pectin:

Pectin is essentially a D-galacturonic acid polymer containing (1-4) links. Pectin is a cheap, non-toxic polysaccharide that is taken out of apple pits or citrus peel. It can also be used as a gelling and thickening agent. When making beads, calcium pectinate is often utilized at a concentration of 1–5%. It is utilized as a carrier material for various controlled release systems and remains stable in low pH solutions. Cross-linked gel beads can be made buoyant by a variety of techniques, some of which include freeze-drying, using volatile or fixed oils, gas-forming chemicals, and more.

7)      Gum karaya:

Gum Karaya dissolves very little in water, very little in 0.1 NHCL, and very little in 95% ethanol. Alkali solutions with PH values above 6.5 and additional similar organic solvents. Gum karaya swells in water and is utilized as a release rate regulating polymer. Zero order medication release and matrix degradation are seen when using this gum.

8)      Psyllium husks:

Psyllium originates from Plantagoovata seed and husk. Psyllium belongs to the class of mucilaginous fibers because of its potent water-forming gelling property. This husk is affordable, readily available, inert, swellable, biocompatible, and environmentally benign. Because of its release-delaying qualities, this husk is a dependable method of delivering medications to the gastrointestinal tract.

9)      Tamarind gum:

The seeds of the Tamarindus Indica tamarind tree are used to make tamarind gum. This gum is a polysaccharide made up of 1:2:3 galactosyl, xylosyl, and glutathione. Xyloglucan, a key structural polysaccharide found in plant main cell walls, is employed in the pharmaceutical industry as a thickening, stabilizing, gelling, and binding agent. Drug release can be studied and a matrix tablet made with tamarind gum is created utilizing the wet granulation technique. Tablet preparation can be done with varying polymer concentrations. An increase in polymer content is associated with a decrease in medication release.

(II)synthetic polymers:

Advantages of synthetic polymers :

·         This type of polymers are inert

·         Also it has a high solubility

·         Mainly it is used in the sustained release preparations

·         Also the synthetic polymers are easily dissolved in water.

Disadvantages of Synthetic Polymer:

·         Toxic

·         Synthetic process is very complicated and high cost

·         Poor biocompatible

·         Acute and chronic adverse effect

There are so many type of Synthetic polymers such as :

1)     HPMC:

HPMC is a semisynthetic polymer that is white to slightly off-white in color, odorless, and tasteless. grainy or fibrous, fluid powder. This is employed in the manufacturing of microspheres and floating tablets. HPMC is a member of the hydrophilic polymer family, which expands when exposed to fluids and forms a gel layer around the polymer matrix's dry core.HPMC are commonly used in oral, ophthalmic, nasal, and topical formulations as binder, emulsifying agent, and thickening agent. They are also utilized as coating solutions for longer release and as tablet binder. There are several molecular weights of HPMC, such as 10,000, 20,000, and 30,000 Dalton.

2)     Ethyl cellulose:

It has a melting point of between 2400 and 25500C, is white in color, and has no flavor or smell. It comes in grades such as K, N, and T type and is not biodegradable in nature. It is also non-toxic and non-irritating. Moreover, it is a long-chain polymer made up of acetal links connecting b-anhydro glucose units. Ethyl cellulose, which is the ethyl ether of cellulose, is used as a coating, filler, and tablet binder as well as an agent to increase viscosity.

3)     Acrylic acid derivatives:

It is derived from the acids methacrylic and acrylic. It is available in many grades, such as Eudragit RL, E, and RS, and is mostly utilized for the manufacturing of floating microspheres. Both RL100 and RS 100 are commonly used granular forms with swelling polymer that is both PH independent and mucoadhesive. Its nature is non-toxic, non-absorbent, and non-biodegradable. Quaternary amino groups are present in grades RS and RL, which are utilized in formulations for prolonged release.

EVALUATION PARAMETERS OF GRDDS: ⁽¹⁸⁾

1. Drug-excipient interaction :

FTIR and HPLC are used in the process. The drug-excipient interaction is indicated by the emergence of a new peak and/or the loss of the original drug or excipient peaks.

2. Floating lag time :

It measures how long it takes for a tablet to come out of the dissolving media and onto the surface. It is expressed in either seconds or minutes.

3. In vitro drug release and duration of floating:

It is ascertained by churning a simulated gastric fluid with a pH of 1.2 at 37±2oC at a speed of 50 or 100 rpm using a USP II equipment (paddle). Samples in aliquots are gathered, and their drug content is examined. The amount of time that the drug floats on the medium's surface is known as the floating time.

4. In vivo evaluation of gastric retention:

Analysis of the position of the dosage form in the GIT involves an imaging technique such as γ-scintigraphy and X-ray.

CONCLUSION

Retention technologies have been thoroughly investigated in recent years for the delivery of medications to the gastrointestinal tract. When taking medications orally, a gastro-retentive strategy can help reduce the frequency of doses and is definitely advantageous for medications in the stomach or upper intestine. To fully utilize the technology, a few obstacles must be removed. The human gastrointestinal tract is unpredictable, which is why many scientists are still figuring out how to exploit it most effectively. The physiological event in the GIT must be taken into account while choosing the right medications and excipient combinations and creating formulation strategies.

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