International Standard Serial Number (ISSN): 2319-8141 .... RPA1300155.pdf · INTERNATIONAL JOURNAL OF UNIVERSAL PHARMACY AND BIO ... processes are extrusion and spheronization and

International Standard Serial Number (ISSN): 2319-8141 International Journal of Universal Pharmacy and Bio Sciences 2(4): July-August 2013

INTERNATIONAL JOURNAL OF UNIVERSAL

PHARMACY AND BIO SCIENCES IMPACT FACTOR 1.89***

ICV 2.40***

Pharmaceutical Sciences Review Article……!!!

Received: 26-07-2013; Accepted: 03-08-2013

MULTIPLE UNIT PELLET SYSTEM – A NEW PATH FOR DRUG DELIVERY

Mr. Pathikkumar J. Maravaniya*, Ms. Tanvee M. Deshpande, Mr. Rohit V. Shinde, Mr.

Ramesh G. Katedeshmukh

Department of Pharmaceutics (M.Pharm), Indira College of Pharmacy, Tathawade, Pune.

KEYWORDS:

MUPS, Pellets,

Pelletization Techniques.

For Correspondence:

Mr. Pathikkumar J.

Maravaniya*

Address: Department

of Pharmaceutics

(M.Pharm), Indira

College of Pharmacy,

Tathawade, Pune.

Email:

pathik.maravaniya@gmai

l.com

ABSTRACT

Compaction of multiparticulates, commonly called MUPS, is one

of the more recent and challenging technologies that combine the

advantages of both tablets and pellet-filled capsules in one dosage

form. Today pelletization represents an efficient pathway for

novel drug delivery in the scope for different oral immediate or

controlled delivery systems. Because of its simple design, high

efficiency of producing spherical pellets and fast processing,

pelletization has found a special position in pharmaceutical

industry. The present article reviews the potential advantages,

desirable properties of pellets, various pelletization techniques,

factors influencing MUPS, drug release mechanisms and various

pharmaceutical applications of multiple unit pellet systems.

401 Full Text Available On www.ijupbs.com

International Standard Serial Number (ISSN): 2319-8141

INTRODUCTION [1-2]:

MUPS is an abbreviation for Multiple-Unit Pellet System. However, from pharmaceutical industry

and research perspective, the term in general refers to MUPS compacted into tablets. Thus, the

resulting tablets prepared by compaction of modified release coated pellets are called as MUPS.

Traditionally, the word “Pellet” has been used to describe a variety of systematically produced,

geometrically defined agglomerates obtained from diverse starting materials utilizing different

processing conditions.

Pelletization is an agglomeration process that converts fine powders or granules of bulk drugs and

excipients into small, free flowing, spherical or semi spherical units, referred to as pellets. Pellets

range in size, typically, between 0.5 – 1.5 mm, though other sizes could be prepared. Pellets are

for pharmaceutical purposes and are produced primarily for the purpose of oral controlled-release

dosage forms having gastro resistant or sustained-release properties or the capability of site-

specific drug delivery. For such purposes, coated pellets are administered in the form of hard

gelatin capsules or disintegrating tablets that quickly liberate their contents of pellets in the

stomach.

As drug delivery systems become more sophisticated, the role of pellets in the design and

development of dosage forms is increasing. Formulation of drugs in multiple-unit dosage forms,

such as coated pellets filled in capsules or compressed into tablets, offers flexibility as to target-

release properties. The safety and efficacy of the formulation is higher than that of other dosage

forms. Pellets provide the development scientist with a high degree of flexibility during the design

and development of oral dosage forms. They can be divided into desired dose strengths without

formulation or process changes, and can also be blended to deliver incompatible bioactive agents

simultaneously or particles with different release profiles at the same site or at different sites

within the gastrointestinal tract. In addition, pellets have numerous therapeutic advantages over

traditional single units, such as tablets and powder-filled capsules. Taken orally, pellets generally

disperse freely in the gastrointestinal tract, and consequently maximize the drug absorption,

minimize local irritation of the mucosa by certain irritant drugs because of the small quantity of

drug available in a single pellet, and reduce inter- and intra-patient variability.

As the advantages of pellets over single units became clear, the pharmaceutical industry as a whole

started to devote resources to conduct research in pellet technology and, whenever possible,

acquire advanced equipment suitable for the manufacture of pellets. Pellets may be manufactured

by using different methods according to the application and the choice of producer. The methods

used for Pelletization are essentially the same as the granulation methods. The most widely used



processes are extrusion and spheronization and solution or suspension layering, and powder

layering. Other processes with limited application in the development of pharmaceutical palletized

products include globulation, balling, and compression.

ADVANTAGES OF MUPS [3-8]:

• They can be divided in to desired dosage strength without process or formulation changes.

• When pellets containing the active ingredient are in the form of suspension, capsules, or

disintegrating tablets, they offer significant therapeutic advantages over single unit dosage forms.

• They can also be blended to deliver incompatible bioactive agents.

• They can also be used to provide different release profile at the same or different sites in the

gastrointestinal tract.

Pellets offer high degree of flexibility in the design and development of oral dosage form like

suspension, sachet, tablet and capsule.

1. Pharmacokinetic advantages:

i. Rapid but uniform transit of micropellets contained in MUPS from the stomach into small

intestine owing to their small size and thus lesser possibility of localized irritation, better and more

uniform drug absorption and greater bioavailability.

ii. Uniform emptying of micropellets from stomach into small intestine facilitates rapid dissolution

of enteric coating and drug release resulting in early tmax and Cmax (peak time and peak plasma

concentration) in case of delayed-release formulations. In case of controlled-release preparations,

drug release is more uniform and possibility of dose dumping is avoided with minimized tendency

for inter-subject variations.

2. Pharmacodynamic advantages:

i. Owing to rapid and uniform gastric emptying and subsequently uniform drug dissolution of

pellets in the gastrointestinal tract due to their small size and larger surface, uniform drug

absorption is facilitated which results in consistent and controlled pharmacological action.

ii. A further reduction in inter- and intra-subject variability in drug absorption and clinical

response is facilitated since the number of pellets per MUPS dosage form is much more than a

conventional pellet-filled capsule and possibility of dose dumping (in stomach) and incomplete

drug release is further minimized.

3. Patient friendly dosage form:

Better patient compliance is expected from MUPS for following reasons –

i. Mouth disintegrating MUPS dosage form having a palatable taste is suitable for pediatric and

Geriatric patients who cannot swallow tablet or capsule, e.g. Prevacid SoluTab.



ii. The orodispersible MUPS medication can be taken without water, especially while travelling

since the dosage form can be designed as orally disintegrating preparation that contains flavors and

sweeteners that stimulate salivation and swallowing, e.g. Prevacid SoluTab.

iii. Being tablets, quite unlike a capsule formulation, MUPS can be also designed into a divisible

dosage form, without compromising the drug release characteristics of coated particles contained

therein.

iv. The MUPS have lesser tendency of adhering to esophagus during swallowing.

v. Smaller volume/size of tablet leads to better patient compliance than capsules.

4. Research, Analysis and Evaluation:

MUPS provide an opportunity to examine the change in size, shape and density of pellets after

compaction by retrieving the pellets from disintegration tubes or from highly lubricated compacts.

Figure 1: Flexibility of pellets in development of dosage form. DISADVANTAGES OF MUPS:

• Dosing by volume rather than number and splitting into single dose units as required.

• Involves capsule filling which can increase the costs or tabletting which destroy film coatings on

the pellets.

• The size of pellets varies from formulation to formulation but usually lies between 1 to 2 mm.

DESIRABLE PROPERTIES OF PELLETS:

• Uncoated pellets:

� Uniform spherical shape,

� Uniform size,

� Good flow properties,

� Reproducible packing,

� High strength,

� Low friability, Low dust,

� Smooth surface,

� Ease of coating.



• Once coated:

� Maintain all of the above properties,

� Have desired drug release characteristics.

(a) (b) (c)

Figure 2: (a) Pellets, (b) Perfect pellet, (c) Coated pellet.

PELLETIZATION TECHNIQUES [9-15]:

The preparation of spherical agglomerates can be approached by several techniques which can be

subdivided into the basic types of systems shown in figure 3.

Figure 3: Different Pelletization Techniques

Pelletization involves the agglomeration of active pharmaceutical ingredients and excipients in

spherical beads called pellets. Variety of techniques is available for pellet manufacturing. Layering

processes have been used over the years. In recent years freeze pelletization, cryopelletization and

hot melt extrusion, extrusion spheronization process have also been used to produce spherical

pellet.


Pelletization

Agitation Compaction Layering Globulation

Balling Compression

Extrusion /

Spheronization

Powder

Solution /

Suspension Spray

Congealing

Spray

Drying


1) Balling:

It describes a Pelletization process in which finely divided particles are converted, upon the

addition of appropriate quantities of liquid, to spherical particles by a continuous rolling or

tumbling motion. The liquid may be added prior to or during the agitation stage. Pans, discs,

drums, or mixers may be used to produce pellets by the balling process.

2) Compression:

It is a pelletization process in which mixtures or blends of active ingredients and excipients are

compacted under pressure to generate pellets of defined shape and size. The pellets are small

enough to be filled into capsules. The formulation and processing variables that govern the

production of pellets during compression are similar to those that are routinely employed in tablet

manufacturing. In fact, pellets produced by compression are nothing but small tablets that are

approximately spherical in shape.

3) Layering:

The layering process comprises the deposition of successive layers of drug entities from solution,

suspension or dry powder on nuclei which may be crystals or granules of the same material or

inert starter seeds. They are classified into two categories: powder layering (Figure 4) and

solution/suspension layering (Figure 5).

Direct pelletizing:

It means manufacturing of pellets directly from powder.

• Effective process: Pellets are manufactured directly from powder with a binder or solvent,

fast process. Low usage of auxiliary materials.

• Product advantages: Compact, round pellets - ideal for automatic dosing and even coating

and Pellet diameter also obtained between 0.2 m m and 1.2 m m.

• Comparison: Pellets have a higher density than spray granulates and agglomerates.

• Process principles: Powder is mixed and moistened. A solvent or binder can also be added.

The powder bed is set into a centrifugal motion. (Fluid Bed Pelletizing in the rotor). The

impact and acceleration forces that occur in this process result in the formation of

agglomerates, which become rounded out into uniform and dense pellets. The speed of

rotation has a direct influence on the density and size of the pellets. The moist pellets are

subsequently dried in the fluid bed. If required, the systems can be made inert for

applications with organic solvents. Another alternative for direct Pelletizing is Spray

Granulation.

• With suitable additives, pellets can be made into tablets or used to fill capsules. The round

shape is ideal for uniform coating. Pellets are good for automatic dosing.



a) Powder Layering:

Powder layering involves the deposition of successive layers of dry powder of drug or

excipients or both on performed nuclei or cores with the help of a binding liquid. Because

powder layering involves the simultaneous application of the liquid and dry powder, it

generally requires specialized equipment. Pieces of equipments revolutionized powder layering

processing as a pelletizing techniques are- tangential spray or centrifugal fluid bed granulators.

In case of tangential spray the rotating disk and fluidization air provides proper mixing.

Figure 4: Principle of powder layering

With a double wall centrifugal granulator, the process is carried out in the open and closed

position. With powder layering, the inner wall is closed so that simultaneous application of

liquid and powder could proceed until the pellets have reached the desired size. The inner wall

is then raised, and the spheres enter the drying zone. The pellets are lifted by the fluidization

air up and over the inner wall back in to forming zone. The cycle is repeated until the desired

residual moisture level in the pellets is achieved.

b) Solution or suspension layering:

Involves the deposition of successive layers of solution and/or suspension of drug substances

and binder on starter seeds, which may be inert materials or crystal/granules of the same drug.

The primary features that distinguish Wurster equipment from other fluid bed equipment are

the cylindrical partition located in the product chamber and the configuration of the air

distribution plate, also known as the orifice plate. The latter is configured to allow most of the

fluidization or drying air to pass at high velocity around nozzle and through the partition,

carrying with it the particles that are being layered on.



Figure 5: Principle of solution and suspension layering

Once the particles exit the partition, they enter the expansion chamber, where the velocity of the

air is reduced below the entrainment velocity, and the particles fall back to the area surrounding

the partition. The down bed is kept aerated by the small fraction of air that passes through the

small holes on the periphery of the orifice plate. The spray direction is concurrent with the particle

movement. The disadvantages of the Wurster process are the inaccessibility of the nozzles. If the

nozzles are clogged at any time during the layering process, the operation has to be interrupted,

and the spray guns must be removed for cleaning. The problem can be alleviated by screening the

formulation or by using a spray gun with a bigger nozzle. Suspension layering is usually used

when the desired drug loading of the pellets is low because production of pellets from low solids

content formulation is not economically feasible.

4) Freeze pelletization:

Freeze pelletization technique is a simple and novel technique for producing spherical matrix

pellets containing active ingredients. In this technique, a molten solid carrier along with a

dispersed active ingredient is introduced as droplets into an inert and immiscible column of liquid.

It is a simple, inexpensive and reproducible technique for producing pellets with varying

properties.

5) Cryopelletization:

Cryopelletization the pellets can be produced by allowing droplets of liquid formulation such as

solution, suspension or emulsion to come in contact with liquid nitrogen at -160 ºC in which liquid

nitrogen used as solidifying medium. These particles are then freeze-dried or lyophilized to

remove water or organic solvents. A major limitation to this process, however, is that it requires



liquid nitrogen. Moreover, the impaction of liquid or semi solid droplets on the surface of the

liquid nitrogen create surface irregularities in the pellets. In addition, pellets produced by freeze-

drying are highly porous and may not be spherical.

6) Hot-Melt Extrusion:

Researchers have investigated a new modified method for preparing matrix pellets for controlled

release drug delivery system to overcome the disadvantages associated with wet mass extrusion

and spheronization process which is called as a Hot Melt Extrusion (HME) method where a

thermal agent softens or gets melted during the process to obtain matrix pellets.

7) Extrusion and Spheronization:

Extrusion spheronization was developed in the early 1960s as a pelletization technique. It used

primarily to produce multiple unit pellets for controlled drug release applications. It is especially

useful for making dense granules with high drug loading for controlled-release oral solid dosage

forms with a minimum amount of excipients. Extrusion spheronization is a multiple process of wet

mass extrusion followed by spheronization to produce uniform size spherical particles called as

spheroids, pellets, beads or matrix pellets depending upon the materials as well as process used for

extrusion spheronization. The major advantage over other methods of producing drug-loaded

spheres or pellets is the ability to incorporate high levels of active ingredients without producing

excessively large particles (i.e. minimal excipients are necessary). Potential applications are many

but relate mainly to controlled drug release and improved processing. The processing steps in the

Extrusion and pelletization are as follows:

a. Dry mixing:

Dry mixing of all ingredients is done to achieve homogeneous powder dispersion using twin shell

blender, plane tray mixer, high speed mixer, and tumbler mixer.

b. Wet massing:

Wet mass extrusion spheronization also called cold-mass extrusion spheronization has become the

method of choice when one is desirous of having dense spherical pellets of uniform size and

shape. Wet massing of powder dispersion is done to produce a sufficient plastic mass for

extrusion.

c. Extrusion:

This is the third step in the process, Extrusion is a method of applying pressure to a mass until it

flows through an orifice or defined opening and produces rod shaped particles of uniform diameter

from the wet mass.

Classification of Extruders: Extruders come in many varieties, but can generally be divided into

three classes, based on their feed mechanism as given in table 1.



Table 1: Types of pharmaceutical extruders

Figure 6: Principle of extruded product spheronization process

d. Spheronization

The function of the fourth step in the process (i.e. spheronization) is to round off the rods produced

by extrusion into spherical particles. The transition from rods to spheres during spheronization

occurs in various stages. If the mass is too dry, spheres will not deform and the rods will only

transform as far as dumbbells. The rounding of the extrudate into spheres is dependent on

frictional forces generated by particle-particle and particle-equipment collisions.

(a) (b)

Figure 7: (a): A Radial pattern with the groves running from the center, (b): A Graphical

representation of the characteristic rope like formation in a spheronizer bowl during operation.

Working Principle: The differential in particle velocity as they move outward to the walls, begin

to climb the walls, and fall back onto the rotating bed, along with the angular motion of the disk,

results in a rope-like formation. A graphic representation of this rope-like formation is shown in

Figure 6.


Sr. No. Extruder Examples

1 Screw fed extruders Axial or End Plate, Dome, Radial

2 Gravity feed extruders Cylinder Roll, Gear roll, Radial

3 Piston feed extruders Ram


e. Drying

A drying stage is required in order to achieve the desired moisture content. The pellets can be

dried at room temperature or at elevated temperature in a tray drier/ oven or in a fluidized bed

drier. When the outlet air reached 50ºC (̴ 30 minutes) drying ended.

MECHANISM OF DRUG RELEASE FROM MUPS: [16]

The mechanism of drug release from MUPS can occur in the following ways:

Diffusion:

On contact with aqueous fluids in the gastrointestinal tract (GIT), water diffuses into the interior of

the particle. Drug dissolution occurs and the drug solutions diffuse across the release coat to the

exterior.

Erosion:

Some coatings can be designed to erode gradually with time, thereby releasing the drug contained

within the particle.

Osmosis:

In allowing water to enter under the right circumstances, an osmotic pressure can be built up

within the interior of the particle. The drug is forced out of the particle into the exterior through

the coating.

FACTORS INFLUENCING DESIGN OF MUPS: [17-20]

Figure 8: Factors influencing design of MUPS



Formulation variables:

The key formulation variables include composition, porosity, size and amount of polymer coating,

nature, size and amount of table ting excipients.

1) Core Pellet:

Pellets are a special form of granulates, characterized by a very regular, round shape, low porosity,

smooth surface and a typical size range of 0.2-2 mm. Depending on the drug distribution inside the

pellets, they can be divided into homogeneous and inhomogeneous pellets (Figure 8).

a) Type and composition:

The multiple unit compositions comprises of enteric coated pellets and at least one tablet

excipient.

b) Size of the pellets:

The size of the pellets also affects the compaction properties and the drug release from the

compacted pellets.

c) Shape of the pellets:

Sphericity of the pellets is the most important characteristics and various methods have been used

to determine it.

d) Porosity of the pellets:

Porosity of the pellets is another key factor that affects the compaction pattern and thereby affects

the polymer coat integrity during compression.

e) Density of the pellets:

Density of pellets of particular importance especially if it is required to achieved prolonged gastric

residence. The use of density as a means of altering the gastric residence time of pharmaceutical

dosage forms (multiple and single units) has little or no value.

f) Elasticity:

Elasticity is directly related to pellet composition. The pellet core should be strong with some

degree of plasticity.

2) Coating:

Polymer coating:

The amount of coating has its own role in protecting the polymer film integrity during

compression. In general, a thicker coating can withstand damage better than a thinner one.



Figure 9: Impact of compaction on pellet deformation and drug release

3) Cushioning excipients:

In order to protect the integrity of coated pellets, excipients with protective (cushioning) properties

are incorporated into tablet formulations. Inclusion of 60-70% cushioning granules into the MUPS

resulted in hard tablets with low friability and consistent drug release profiles.

PHARMACEUTICAL APPLICATIONS OF MUPS: [20]

These solid dosage forms are mostly in the form of tablets or capsules containing high levels of an

Active Pharmaceutical Ingredient (API). Product characteristics include:

• Dense pellets

• Smooth coatable pellets

• Narrow particle size distributions, and

• High yield and flow ability

Important pharmaceutical applications include:

• Controlled release pellets for encapsulations

• Sustained release pellets / Delayed release enteric coated pellets

• Multi-particulate systems

• Multi-unit erosion matrix pellets

• Pellets for special tabletting applications

• Immediate release pellets for sachets

CONCLUSION:

Thus it can be concluded that multiple unit pellet system can be considered as a most promising

drug delivery system today which is catching up with the pace to have a high existence in the



Pharma world. These drug delivery systems have gained popularity in the recent times since they

provide several advantages including greater flexibility and adaptability of microparticulate dosage

forms which gives clinicians and those engaged in product development powerful new tools to

optimize therapy.

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International Standard Serial Number (ISSN): 2319-8141 .... RPA1300155.pdf · INTERNATIONAL JOURNAL OF UNIVERSAL PHARMACY AND BIO ... processes are extrusion and spheronization and