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Asian J. Pharm. Res. 2012; Vol. 2: Issue 1, Pg 07-18 

[AJPRes.] 

ISSN- 2231–5683 (Print) 

www.asianpharmaonline.org 

ISSN- 2231–5691 (Online) 0974-3618 

REVIEW ARTICLE 

Floating drug delivery system: An innovative acceptable approach in 

Gastro retentive drug delivery. 

Nirav Patel 1 , Nagesh C. 1 *, Chandrashekhar S. 1 , Patel Jinal 2 and Jani Devdatt 1 

1 Maratha Mandal’s College of Pharmacy, Belgaum-590016, Karanataka. 

2 A.P.M.C. college of Pharmaceutical Education and Research, Motipura, Himatnagar-383001, Gujarat. 

*Corresponding Author E-mail: nagesh_73@rediffmail.com 

ABSTRACT: 

Controlled release (CR) dosage forms have been extensively used to improve therapy with several important drugs. 

The recent developments of floating drug delivery systems (FDDS) including the physiological and formulation 

variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their 

classification and formulation aspects are covered in detail. This review also summarizes the in vitro techniques, in 

vivo studies to evaluate the performance and application of floating systems. Floating dosage form can be prepared as 

tablets, capsules by adding suitable ingredients as well as by adding gas generating agent. In this review various 

techniques used in floating dosage forms along with current & recent developments of stomach specific floating drug 

delivery system for gastro retention are discussed. 

KEYWORDS: Floating drug delivery systems, mechanism, single unit, multiple units, evaluation Method. 

INTRODUCTION: 

Oral administration is the most versatile, convenient and 

commonly employed route of drug delivery for systemic 

action. Indeed, for controlled release system, oral route of 

administration has received the more attention and success 

because gastrointestinal physiology offers more flexibility 

in dosage form design than other routes. Development of a 

successful oral controlled release drug delivery dosage form 

requires an understanding of three aspects: 

(1) Gastrointestinal (GI) physiology 

(2) Physiochemical properties of the drug and 

(3) Dosage form characteristics 1, 2 . 

Gastric emptying of dosage forms is an extremely variable 

process and ability to prolong and control the emptying 

time is a valuable asset for dosage forms, which reside in 

the stomach for a longer period of time than conventional 

dosage forms 3 . 

1.Phase I (Basal phase) lasts from 30 to 60 minutes with 

rare contractions. 

2. Phase II (Preburst phase) lasts for 20 to 40 minutes with 

intermittent action potential and contractions. As the phase 

progresses the intensity and frequency also increases 

gradually. 

3. Phase III (burst phase) lasts for 10 to 20 minutes. It 

includes intense and regular contractions for short period. It 

is due to this wave that all the undigested material is swept 

out of the stomach down to the small intestine. It is also 

known as the housekeeper wave. 

4. Phase IV lasts for 0 to 5 minutes and occurs between 

phases III and I of 2 consecutive cycles 4 . (Figure 1) 

Gastric emptying occurs during fasting as well as fed states. 

The pattern of motility is however distinct in the 2 states. 

During the fasting state an interdigestive series of electrical 

events take place, which cycle both through stomach and 

intestine every 2 to 3 hours. This is called the interdigestive 

myloelectric cycle or migrating myloelectric cycle (MMC), 

which is further divided into following 4 phases 

Received on 09.01.2012 Accepted on 24.02.2012 

© Asian Pharma Press All Right Reserved 

Asian J. Pharm. Res. 2(1): Jan.-Mar. 2012; Page 07-18 

7 

Fig. 1: Motility pattern in GIT


Gastroretentive systems can remain in the gastric region for 

several hours and hence significantly prolong the gastric 

residence time of drugs. Prolonged gastric retention 

improves bioavailability, reduces drug waste, and improves 

solubility for drugs that are less soluble in a high pH 

environment. It has applications also for local drug delivery 

to the stomach and proximal small intestines. Slowed 

motility of the gastrointestinal tract by concomitant 

administration of drugs or pharmaceutical excipients also 

increase gastric retention of drug 5 . 

These efforts resulted in GRDFs that were designed, in 

large part, based on the following approaches. (Figure 2) 

1. Low density form of the DF that causes buoyancy in 

gastric fluid 6, 7 

2. High density DF that is retained in the bottom of the 

stomach 8, 9 

3. Bioadhesion to stomach mucosa 10 

4. Expansion by swelling or unfolding to a large size 

which limits passage of dosage form through the 

pyloric sphincter 11 

[AJPRes.] 

FACTORS AFFECTING GASTRIC RESIDENCE 

TIME OF FDDS 

a) Formulation factors 

Size of tablets 

Retention of floating dosage forms in stomach depends on 

the size of tablets. Small tablets are emptied from the 

stomach during the digestive phase, but large ones are 

expelled during the house keeping waves 4 . 

Floating and nonfloating capsules of 3 different sizes 

having a diameter of 4.8 mm (small units), 7.5 mm 

(medium units), and 9.9 mm (large units), were formulated 

and analyzed for their different properties. It was found that 

floating dosage units remained buoyant regardless of their 

sizes on the gastric contents throughout their residence in 

the gastrointestinal tract, while the nonfloating dosage units 

sank and remained in the lower part of the stomach. 

Floating units away from the gastroduodenal junction were 

protected from the peristaltic waves during digestive phase 

while the nonfloating forms stayed close to the pylorus and 

were subjected to propelling and retropelling waves of the 

digestive phase 15 . 

Density of tablets 

Density is the main factor affecting the gastric residence 

time of dosage form. A buoyant dosage form having a 

density less than that of the gastric fluids floats, since it is 

away from the pyloric sphincter, the dosage unit is retained 

in the stomach for a prolonged period. A density of less 

than 1.0g/ml i.e. less than that of gastric contents has been 

reported. However, the floating force kinetics of such 

dosage form has shown that the bulk density of a dosage 

form is not the most appropriate parameter for describing its 

buoyancy capabilities 16 . 

Shape of tablets 

The shape of dosage form is one of the factors that affect its 

gastric residence time. Six shapes (ring tetrahedron, 

cloverleaf, string, pellet, and disk) were screened in vivo for 

their gastric retention potential. The tetrahedron (each leg 

2cm long) rings (3.6 cm in diameter) exhibited nearly 100% 

retention at 24 hr 17 . 

Fig. 2: Different approaches of gastric retention 

Novel oral controlled dosage form that is retained in the 

stomach for prolonged and predictable period is of major 

interest among academic and industrial research groups. 

One of the most feasible approaches for achieving 

prolonged and predictable drug delivery profile in the GI 

tract is to control gastric residence time (GRT). Dosage 

form with prolonged GRT or gastro-retentive dosage form 

(GRDF) provides an important therapeutic option 12 . Various 

approaches for preparation of gastroretentive drug delivery 

system include floating systems, swellable and expandable 

systems, high density systems, bioadhesive systems, altered 

shape systems, gel forming solution or suspension system 

and sachet systems. Among these, the floating dosage form 

has been used most commonly 13, 14 . 

Viscosity grade of polymer 

Drug release and floating properties of FDDS are greatly 

affected by viscosity of polymers and their interaction. Low 

viscosity polymers (e.g., HPMC K100 LV) were found to 

be more beneficial than high viscosity polymers (e.g., 

HPMC K4M) in improving floating properties. In addition, 

a decrease in the release rate was observed with an increase 

in polymer viscosity 18 . 

b) Idiosyncratic factors 

Gender 

Women have slower gastric emptying time than do men. 

Mean ambulatory GRT in meals (3.4±0.4 hours) is less 

compared with their age and racematched female 

counterparts (4.6±1.2 hours), regardless of the weight, 

height and body surface 19 . 

8


Age 

Low gastric emptying time is observed in elderly than do in 

younger subjects. Intrasubject and intersubject variations 

also are observed in gastric and intestinal transit time. 

Elderly people, especially those over 70 years have a 

significantly longer GRT 20 . 

Posture 

i) Upright position 

An upright position protects floating forms against 

postprandial emptying because the floating form remains 

above the gastric contents irrespective of its size 20 . Floating 

dosage forms show prolonged and more reproducible GRTs 

while the conventional dosage form sink to the lower part 

of the distal stomach from where they are expelled through 

the pylorus by antral peristaltic movements 21 . 

ii) Supine position 

This position offers no reliable protection against early and 

erratic emptying. In supine subjects large dosage forms 

(both conventional and floating) experience prolonged 

retention. The gastric retention of floating forms appear to 

remain buoyant anywhere between the lesser and greater 

curvature of the stomach. On moving distally, these units 

may be swept away by the peristaltic movements that 

propel the gastric contents towards the pylorus, leading to 

significant reduction in GRT compared with upright 

subjects 22 . 

Concomitant intake of drugs 

Drugs such as prokinetic agents (e.g., metoclopramide and 

cisapride), anti Cholinergics (e.g., atropine or 

propantheline), opiates (e.g., codeine) may affect the 

performance of FDDS. The coadministration of GImotility 

decreasing drugs can increase gastric emptying time 22 . 

Feeding regimen 

Gastric residence time increases in the presence of food, 

leading to increased drug dissolution of the dosage form at 

the most favorable site of absorption. A GRT of 410 h has 

been reported after a meal of fats and proteins 23 . 

[AJPRes.] 

FLOATING DRUG DELIVERY SYSTEM: 

Mechanism of floating systems: 

Various attempts have been made to retain the dosage form 

in the stomach as a way of increasing the retention time. 

These attempts include introducing floating dosage forms 

(gas-generating systems and swelling or expanding 

systems), mucoadhesive systems, high-density systems, 

modified shape systems, gastric-emptying delaying devices 

and co-administration of gastric emptying delaying drugs. 

Among these, the floating dosage forms are the most 

commonly used. Floating drug delivery systems (FDDS) 

have a bulk density less than gastric fluids and so remain 

buoyant in the stomach without affecting the gastric 

emptying rate for a prolonged period of time. While the 

system is floating on the gastric contents (given in the Fig. 

3A), the drug is released slowly at the desired rate from the 

system. After release of drug, the residual system is 

eliminated from the stomach. This results in an increased 

GRT and a better control of the fluctuations in plasma drug 

concentration. However, besides a minimal gastric content 

needed to allow the proper achievement of the buoyancy 

retention effect, a minimal level of floating force (F) is also 

required to maintain the buoyancy of the dosage form on 

the surface of the meal. To measure the floating force 

kinetics, a novel apparatus for determination of resultant 

weight has been reported in the literature. The apparatus 

operates by measuring continuously the force equivalent to 

F (as a function of time) that is required to maintain a 

submerged object. The object floats better if F is on the 

higher positive side (Fig. 3B). This apparatus helps in 

optimizing FDDS with respect to stability and sustainability 

of floating forces produced in order to prevent any 

unforeseeable variations in intragastric buoyancy 12 . 

F = Fbuoyancy – Fgravity = (Df – Ds) g v 

Where, F = total vertical force, 

Df = fluid density, 

Ds = object density, 

v = volume and 

g = acceleration due to gravity 24 . 

Fig. 3. Mechanism of floating systems. 

9


CLASSIFICATION: 

Floating Oral Drug Delivery System (FDDS) are retained in 

the stomach and are useful for drugs that are poorly soluble 

or unstable in intestinal fluids. Floating drug delivery 

system (FDDS) have a bulk density less than gastric fluids 

and so remain buoyant in the stomach without affecting the 

gastric emptying rate for a prolonged period of time 13 . 

While the system is floating on the gastric contents, the 

drug is released slowly at the desired rate from the system 

(Figure 4). After release of drug, the residual system is 

emptied from the stomach. This results in an increased GRT 

and a better control of fluctuations in plasma drug 

concentration. 

Fig. 4: Intragastric residence positions of floating unit. 

[AJPRes.] 

A. Single unit floating system 

a) Noneffervescent system 

Hydrodyanamic balanced systems 

Sheth and Tossounian first designated this 

‘hydrodynamically balanced system’. Such a system 

contains drug with gel-forming hydrocolloids meant to 

remain buoyant on the stomach content. This prolongs GRT 

and maximizes the amount of drug that reaches its 

absorption sites in the solution form for ready absorption 

(Figure 5). This system incorporates a high level of one or 

more gel-forming highly soluble cellulose type 

hydrocolloid, e.g., hydroxypropylcellulose, hydoxyethyl 

cellulose, hydroxypropyl methyl cellulose (HPMC), 

polysaccharides and matrix-forming polymer such as 

polycarbophil, polyacrylate and polystyrene. On coming in 

contact with gastric fluid, the hydrocolloid in the system 

hydrates and forms a colloid gel barrier around its surface 25 . 

Yang et al developed a swellable asymmetric triple-layer 

tablet with floating ability to prolong the gastric residence 

time of triple drug regimen (tetracycline, metronidazole, 

and clarithromycin) in Helicobacter pylori–associated 

peptic ulcers using hydroxy propyl methyl cellulose 

(HPMC) and poly (ethylene oxide) (PEO) as the rate 

controlling polymeric membrane excipients. Bismuth salt 

was included in one of the outer layers for instant release. 

The floatation was accomplished by incorporating a gas 

generating layer consisting of sodium bicarbonate: calcium 

carbonate (1:2 ratios) along with the polymers 26 . (Figure 6). 

Fig.5: Hydrodynamically balanced system (HBS). The gelatinous polymer barrier formation results from hydrophilic polymer swelling. 

Drug is released by diffusion and erosion of the gel barrier. 

Fig. 6: Schematic presentation of working of a triple-layer system. (A) Initial configuration of triple-layer tablet. (B) On contact with the 

dissolution medium the bismuth layer rapidly dissolves and matrix starts swelling. (C) Tablet swells and erodes. (D) and (E) Tablet 

erodes completely. 

10


[AJPRes.] 

Floating chamber 

Fluid- filled floating chamber which includes incorporation 

of a gas-filled floatation chamber into a microporous 

component that houses a drug reservoir. Apertures or 

openings are present along the top and bottom walls 

through which the gastrointestinal tract fluid enters to 

dissolve the drug. The other two walls in contact with the 

fluid are sealed so that the undissolved drug remains 

therein. The fluid present could be air, under partial vacuum 

or any other suitable gas, liquid, or solid having an 

appropriate specific gravity and an inert behaviour. The 

device is of swallowable size, remains a float within the 

stomach for a prolonged time, and after the complete 

release the shell disintegrates, passes off to the intestine, 

and is eliminated 27 . (Figure 7) 

b) Effervescent Floating Dosage Forms Gas Generating 

Systems: 

Floating systems containing effervescent components 

These are matrix type of systems prepared with the help of 

swellable polymers such as methylcellulose and chitosan 

and various effervescent compounds, e.g., sodium 

bicarbonate, tartaric acid, and citric acid. They are 

formulated in such a way that when in contact with the 

acidic gastric contents, co 2 is liberated and gets entrapped in 

swollen hydrocolloids, which provide buoyancy to the 

dosage forms. In vitro, the lag time before the unit floats is 


[AJPRes.] 

Programmable drug delivery 

A programmable, controlled release drug delivery system 

has been developed in the form of a non-digestible oral 

capsule (containing drug in a slowly eroding matrix for 

controlled release) was designed to utilize an automatically 

operated geometric obstruction that keeps the device 

floating in the stomach and prevents it from passing through 

the remainder of the GIT. Different viscosity grades of 

hydroxypropyl-methyl-cellulose were employed as model 

eroding matrices. The duration during which the device 

could maintain its geometric obstruction (caused by a builtin 

triggering ballooning system) was dependent on the 

erosion rates of the incorporated polymers (the capsule inhosed 

core matrix). After complete core matrix erosion, the 

ballooning system is automatically flattened off so that the 

device retains its normal capsule size to be eliminated by 

passing through the GIT 32 . 

B. Multiple unit floating system 

a) Non-effervescent Systems: 

Alginate beads 

Alginates have received much attention in the development 

of multiple unit systems. Alginates are nontoxic, 

biodegradable linear copolymers composed of L-glucuronic 

and L-mannuronic acid residues. Multiple unit floating 

dosage forms have been developed from freezedried 

calcium alginate. Spherical beads of approximately 2.5 mm 

in diameter can be prepared by dropping a sodium alginate 

solution in to aqueous solutions of calcium chloride, 

causing precipitation of calcium alginate. The beads are 

then separated snap and frozen in liquid nitrogen, and freeze 

dried at -40°C for 24 hours, leading to the formation of 

porous system, which can maintain a floating force over 12 

hours 33, 34 . A multiple unit system can be developed 

comprising of calcium alginate core and calcium 

alginate/PVA membrane, both separated by an air 

compartment. Air compartment provides bouncy to beads. 

In presence of water, the PVA leaches out and increases the 

membrane permeability, maintaining the integrity of the air 

compartment. Increase in molecular weight and 

concentration of PVA, resulted in enhancement of the 

floating properties of the system 35 . 

(A) 

(B) 

Fig. 9: (A) Multiple-unit oral floating drug delivery system. (B) 

Working principle of effervescent floating drug delivery system. 

C) Hollow Microspheres: 

Hollow microspheres are considered as one of the most 

promising buoyant systems, as they possess the unique 

advantages of multiple unit systems as well as better 

floating properties, because of central hollow space inside 

the microsphere(Figure 10). The general techniques 

involved in their preparation include simple solvent 

evaporation, and solvent diffusion and evaporation. 

Polycarbonate, Eudragit S, cellulose acetate, calcium 

alginate, agar and low methoxylated pectin are commonly 

used as polymers in preparation of hollow microsphere. 

Buoyancy and drug release are dependent on quantity of 

polymer, the plasticizer–polymer ratio and the solvent 

used 7, 37, 38 . 

b) Effervescent systems: 

Floating pills 

Ichikawa et al developed a new multiple type of floating 

dosage system composed of effervescent layers and 

swellable membrane layers coated on sustained release 

pills. The inner layer of effervescent agents containing 

sodium bicarbonate and tartaric acid was divided into 2 

sublayers to avoid direct contact between the 2 agents. This 

is surrounded by a swellable polymer membrane containing 

polyvinyl acetate and purified shellac. When this system 

was immersed in the buffer at 37ºC, produce swollen pills 

(like balloons) with a density less than 1.0 g/mL due to 

incorporation of co 2 36 .(Figure 9) 

12 

Fig. 10: Micro balloons


[AJPRes.] 

D. Raft forming system 

Raft-forming systems 

On contact with Gastric fluid A gel-forming solution (e.g. 

sodium alginate solution containing carbonates or 

bicarbonates) swells and forms a viscous cohesive gel 

containing entrapped CO 2 bubbles. This forms raft layer on 

top of gastric fluid which releases drug slowly in stomach. 

Such formulation typically contains antacids such as 

aluminium hydroxide or calcium carbonate to reduce gastric 

acidity. They are often used for gastro esophageal reflux 

treatment as with Liquid Gaviscon (GlaxoSmithKline) 39 . 

(Figure 11) 

Fig. 11: Barrier formed by a raft-forming system 

Drugs Used In the Formulations of Stomach Specific 

Floating Dosage Forms 

1. Floating microspheres – Aspirin, Griseofulvin, 

pnitroaniline, Ibuprofen, Ketoprofen 40 , Piroxicam, 

Verapamil HCl, Cholestyramine, Theophylline, 

Nifedipine, Nicardipine, Dipyridamol, Tranilast 41 and 

Terfinadine 42 

2. Floating granules - Diclofenac sodium, Indomethacin 

and Prednisolone 

1. Films 43 – Cinnarizine, Albendazole 

1. Floating tablets and Pills - Isosorbide mononitrate 37 , 

Diltiazem 44 , Acetylsalicylic acid 45 , Piretanide 46 , 

Sotalol 47 , carbamazepine, Furosamide 48 , 

Pentoxyphylline 49 , captopril 50 , Nimodipine 51 , 

Acetaminophen 52 , Amoxicillin trihydrate 53 , Diazepam 54 

2. Floating Capsules –Diazepam 55 , Ursodeoxycholic 

acid 49 , Verapamil HCl 56 , Nicardipine 57 , Furosemide 58 , 

Misoprostal 4 

Table 1. Marketed Preparations of Floating Drug Delivery 

Systems: 

S. 

no. 

Product Active Ingredient Reference 

No. 

1 Madopar Levodopa and benserzide 59 

2 Valrelease Diazepam 25 

3 Topalkan Aluminum magnesium 

60 

antacid 

4 Almagate Antacid 61 

flatcoat 

5 Liquid 

gavison 

Alginic acid and sodium 

bicarbonate 

62 

13 

Application: 

Floating drug delivery offers several applications for drugs 

having poor bioavailability because of the narrow 

absorption window in the upper part of the gastrointestinal 

tract. It retains the dosage form at the site of absorption and 

thus enhances the bioavailability. These are summarized as 

follows. 

1. Sustained Drug Delivery 

HBS systems can remain in the stomach for long periods 

and hence can release the drug over a prolonged period of 

time. The problem of short gastric residence time 

encountered with an oral CR formulation hence can be 

overcome with these systems. These systems have a bulk 

density of G1 as a result of which they can float on the 

gastric contents. These systems are relatively large in size 

and passing from the pyloric opening is prohibited. 

Recently sustained release floating capsules of nicardipine 

hydrochloride were developed and were evaluated in vivo. 

The formulation compared with commercially available 

MICARD capsules using rabbits. Plasma concentration time 

curves showed a longer duration for administration (16 

hours) in the sustained release floating capsules as 

compared with conventional MICARD capsules (8 hours) 

57 . Similarly a comparative study between the Madopar 

HBS and Madopar standard formulation was done and it 

was shown that the drug was released up to 8 hours in vitro 

in the former case and the release was essentially complete 

in less than 30 minutes in the latter case 59 . 

2. Site-Specific Drug Delivery 

These systems are particularly advantageous for drugs that 

are specifically absorbed from stomach or the proximal part 

of the small intestine, e.g. riboflavin and furosemide. 

Furosemide is primarily absorbed from the stomach 

followed by the duodenum. It has been reported that a 

monolithic floating dosage form with prolonged gastric 

residence time was developed and the bioavailability was 

increased. AUC obtained with the floating tablets was 

approximately 1.8 times those of conventional furosemide 

tablets 58 . A bilayer-floating capsule was developed for local 

delivery of misoprostol, which is a synthetic analog of 

prostaglandin E1 used as a protectant of gastric ulcers 

caused by administration of NSAIDs. By targeting slow 

delivery of misoprostol to the stomach, desired therapeutic 

levels could be achieved and drug waste could be reduced 4 . 

3. Absorption Enhancement: 

Drugs that have poor bioavailability because of sitespecific 

absorption from the upper part of the gastrointestinal tract 

are potential candidates to be formulated as floating drug 

delivery systems, thereby maximizing their absorption. 

E.g. A significantly increase in the bioavailability of 

floating dosage forms(42.9%) could be achieved as 

compared with commercially available LASIX tablets 

(33.4%) and enteric coated LASIX-long product (29.5%) 57 .


[AJPRes.] 

EVALUATION OF GASTRORETENTIVE 

DOSAGEFORM 

A) IN-VITRO EVALUATION 62 , 63 

i) Floating systems 

a) Buoyancy Lag Time 

It is determined in order to assess the time taken by the 

dosage form to float on the top of the dissolution medium, 

after it is placed in the medium. These parameters can be 

measured as a part of the dissolution test 64 . 

b) Floating Time 

Test for buoyancy is usually performed in SGF-Simulated 

Gastric Fluid maintained at 37 0 C. The time for which the 

dosage form continuously floats on the dissolution media is 

termed as floating time 65 . 

c) Specific Gravity / Density 

Density can be determined by the displacement method 

using Benzene as displacement medium. 

d) Resultant Weight 

Now we know that bulk density and floating time are the 

main parameters for describing buoyancy. But only single 

determination of density is not sufficient to describe the 

buoyancy because density changes with change in resultant 

weight as a function of time. 

For example a matrix tablet with bicarbonate and matrixing 

polymer floats initially by gas generation and entrapment 

but after some time, some drug is released and 

simultaneously some outer part of matrixing polymer may 

erode out leading to change in resultant weight of dosage 

form. The magnitude and direction of force/resultant weight 

(up or down) is corresponding to its buoyancy force 

(Fbuoy) and gravity force (Fgrav) acting on dosage form 

F = F buoy - F grav F = D f g V – D s g V F = (D f – D s ) g V 

F = (D f – M/V) g V 

Where, 

F = resultant weight of object 

D f = Density of Fluid 

D S = Density of Solid object 

g = Gravitational force 

M = Mass of dosage form 

V = Volume of dosage form 

So when Ds, density of dosage form is lower, F force is 

positive gives buoyancy and when it is Ds is higher, F will 

negative shows sinking 21 . 

ii) Swelling systems 

a) Swelling Index 

After immersion of swelling dosage form into SGF at 37 0 C, 

dosage form is removed out at regular interval and 

dimensional changes are measured in terms of increase in 

tablet thickness / diameter with time. 

b) Water Uptake 

It is an indirect measurement of swelling property of 

swellable matrix. Here dosage form is removed out at 

regular interval and weight changes are determined with 

respect to time. So it is also termed as Weight Gain. 

Water uptake = WU = (Wt – Wo) * 100 / Wo 

Where, Wt = weight of dosage form at time t 

Wo = initial weight of dosage form 

B) IN-VITRO DISSOLUTION TESTS 

A. In vitro dissolution test is generally done by using USP 

apparatus with paddle and GRDDS is placed normally as 

for other conventional tablets. But sometimes as the vessel 

is large and paddles are at bottom, there is much lesser 

paddle force acts on floating dosage form which generally 

floats on surface. As floating dosage form not rotates may 

not give proper result and also not reproducible results. 

Similar problem occur with swellable dosage form, as they 

are hydrogel may stick to surface of vessel or paddle and 

gives irreproducible results. In order to prevent such 

problems, various types of modification in dissolution 

assembly made are as follows. 

B. To prevent sticking at vessel or paddle and to improve 

movement of dosage form, method suggested is to keep 

paddle at surface and not too deep inside dissolution 

medium. 

14


[AJPRes.] 

Fig. 12 dissolution of floating dosage form 

C. Floating unit can be made fully submerged, by attaching 

some small, loose, non- reacting material, such as few turns 

of wire helix, around dosage form. However this method 

can inhibit three dimensional swelling of some dosage form 

and also affects drug release. 

D. Other modification is to make floating unit fully 

submerged under ring or mesh assembly and paddle is just 

over ring that gives better force for movement of unit. 

E. Other method suggests placing dosage form between 2 

ring/meshes. 

F. In previous methods unit have very small area, which 

can inhibit 3D swelling of swellable units, another method 

suggest the change in dissolution vessel that is indented at 

some above place from bottom and mesh is place on 

indented protrusions, this gives more area for dosage form. 

G. Inspite of the various modifications done to get the 

reproducible results, none of them showed co-relation with 

the in-vivo conditions. So a novel dissolution test apparatus 

with modification of Rossett-Rice test Apparatus was 

proposed 65, 67 . 

C) IN-VIVO EVALUATION 

a) Radiology 

X-ray is widely used for examination of internal body 

systems. Barium Sulphate is widely used Radio Opaque 

Marker. So, BaSO 4 is incorporated inside dosage form and 

X-ray images are taken at various intervals to view GR. 

b) Scintigraphy 

Similar to X-ray, emitting materials are incorporated into 

dosage form and then images are taken by scintigraphy. 

Widely used emitting material is 99 Tc. 

c) Gastroscopy 

Gastroscopy is peroral endoscopy used with fiber optics or 

video systems. Gastroscopy is used to inspect visually the 

effect of prolongation in stomach. It can also give the 

detailed evaluation of GRDDS. 

d) Magnetic Marker Monitoring 

In this technique, dosage form is magnetically marked with 

incorporating iron powder inside, and images can be taken 

by very sensitive bio-magnetic measurement equipment. 

Advantage of this method is that it is radiation less and so 

not hazardous. 

e) Ultrasonography 

Used sometimes, not used generally because it is not 

traceable at intestine. 

f) 13 C Octanoic Acid Breath Test 

13 C Octanoic acid is incorporated into GRDDS. In stomach 

due to chemical reaction, octanoic acid liberates CO 2 gas 

which comes out in breath. The important Carbon atom 

which will come in CO 2 is replaced with 13 C isotope. So 

time up to which 13 CO 2 gas is observed in breath can be 

considered as gastric retention time of dosage form. As the 

dosage form moves to intestine, there is no reaction and no 

CO 2 release. So this method is cheaper than other. 

ADVANTAGES: 

1. Enhanced bioavailability the bioavailability of some 

drugs (e.g. riboflavin and levodopa) CR-GRDF is 

significantly enhanced in comparison to administration of 

non- GRDF CR polymeric formulations 68 . 

2. Enhanced first-pass biotransformation when the drug 

is presented to the metabolic enzymes (cytochrome P-450, 

in particular CYP-3A4) in a sustained manner, the 

presystemic metabolism of the tested compound may be 

considerably increased rather than by a bolus input 69 . 

3. Sustained drug delivery/reduced frequency of dosing 

the drugs having short biological half life, a sustained and 

slow input from FDDS may result in a flip-flop 

pharmacokinetics and it reduces the dose frequency. This 

feature is associated with improved patient compliance and 

thus improves the therapy 69 . 

4. Targeted therapy for local ailments in the upper GIT 

the prolonged and sustained administration of the drug from 

15


[AJPRes.] 

FDDS to the stomach may be useful for local therapy in the 

stomach. 

5. Reduced fluctuations of drug concentration the 

fluctuations in plasma drug concentration are minimized, 

and concentration-dependent adverse effects that are 

associated with peak concentrations can be prevented. This 

feature is of special importance for drugs with a narrow 

therapeutic index 70 . 

6. Improved receptor activation selectivity FDDS reduces 

the drug concentration fluctuation that makes it possible to 

obtain certain selectivity in the elicited pharmacological 

effect of drugs that activate different types of receptors at 

different concentrations 69 . 

7. Reduced counter-activity of the body slow release of 

the drug into the body minimizes the counter activity 

leading to higher drug efficiency. 

8. Extended time over critical (effective) concentration 

the sustained mode of administration enables extension of 

the time over a critical concentration and thus enhances the 

pharmacological effects and improves the clinical 

outcomes. 

9. Minimized adverse activity at the colon Retention of 

the drug in GRDF at stomach minimizes the amount of 

drugs that reaches the colon and hence prevents the 

degradation of drug that degraded in the colon. 

10. Site specific drug delivery a floating dosage form is a 

widely accepted approach especially for drugs which have 

limited absorption sites in upper small intestine. 

71, 72 

Limitations/Disadvantages 

1. These systems require a high level of fluid in the 

stomach for drug delivery tom float and work 

efficiently-coat, water. 

2. Not suitable for drugs that have solubility or stability 

problem in GIT. 

3. Drugs such as Nifedipine which is well absorbed along 

the entire GIT and which undergoes first pass 

metabolism, may not be desirable. 

4. Drugs which are irritant to Gastric mucosa are also not 

desirable or suitable. 

5. The drug substances that are unstable in the acidic 

environment of the stomach are not suitable candidates 

to be incorporated in the systems. 

6. The dosage form should be administered with a full 

glass of water (200-250 ml). 

These systems do not offer significant advantages over the 

conventional dosage forms for drugs, which are absorbed 

throughout the gastrointestinal tract. 

CONCLUSION: 

Drug absorption in the gastrointestinal tract is a highly 

variable procedure and prolonging gastric retention of the 

dosage form extends the time for drug absorption. FDDS 

16 

promises to be a potential approach for gastric retention. 

The FDDS proves advantageous for drugs that are absorbed 

primarily in the upper segments of GI tract, i.e., the 

stomach, duodenum, and jejunum when compared to the 

conventional dosage form. Due to the complexity of 

pharmacokinetic and pharmacodynamic parameters, in vivo 

studies are required to establish the optimal dosage form for 

a specific drug. For a certain drug, interplay of its 

pharmacokinetic and pharmacodynamic parameters will 

determine the effectiveness and benefits of the CRGRDF 

compared to the other dosage forms. 

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