TABLETS

UNIT II
A. TABLETS
Ms. TENY SARA THOMAS
MOUNT ZION COLLEGE OF PHARMACEUTICAL
SCIENCES AND RESEARCH, ADOOR, KERALA
ASSISTANT PROFESSOR
B.PHARM FIFTH SEMESTER
FORMULATIVE & INDUSTRIAL PHARMACY

CONTENTS
 Introduction
 Classification of Tablets
 Excipients used in Formulating Tablets
 Tablet Granulation & Its Importance
 Methods of Granulation
 Tablet Compression Machines
 Equipment tooling
 Compression Processing Problems during Tablet
Manufacturing Process

INTRODUCTION
Pharmaceutical Tablets :- are solid dosage
forms containing one or more drugs with or
without the addition of excipients.
Addictives or excipients are mainly
incorporated to enhance physical appearance,
stability, disintegration, or breakup of tablet after
administration.
According to Indian Pharmacopoeia,
pharmaceutical tablets are flat or bi-convex
discs manufactured by compressing a drug or
a mixture of rugs with or without suitable
excipients.

Ideal Characteristics of Tablets
The objective of the design and manufacture of the
compressed tablet is to deliver orally the correct amount of
drug in the proper form, at or over the proper time and in the
desired location, and to have its chemical integrity protected.
Should be an elegant product, free from defects.
Should have strength to withstand the harshness of
mechanical shock that can be encountered in its production,
packaging, shipping etc.
Must be able to release the medicinal agent in the body in a
predictable and reproducible manner.
Must be uniform in weight and drug content.
Size and shape of tablets influence the passing of product
through GIT.
Tablets should be physically and chemically stable so that no
alternation of Active ingredient with time.

Advantages of Tablets
Cheapest oral dosage form, easy to handle,
convenient to administer and offers greatest dose
precision.
Have the best combined properties of chemical,
mechanical, and microbiological stability of all the
oral forms.
Greatest ease of swallowing, and less shelf storage
space.
Suitable for large scale production
Unpleasant and bitter tasting drugs when
formulating, the taste can be masked with excipients
suitable.
Provide protection of medicaments from

Disadvantages of Tablets
Some of drugs, due to their highly amorphous nature
and low density, are difficult to compress.
Chances of loss of ingredients of tablets during
manufacturing because of involvement of several unit
of operation.
Drugs with poor wetting properties and slow
dissolution rate are difficult to be dispensed in the
form of tablets.
Drugs with objectionable odour and bitter tasting
substance need special treatment for compression.
This can increase the cost of production.
Bioavailability problems may arise due to slow
disintegration and slow dissolution
Some drugs can cause irritant effect on the GIT.

CLASSIFICATION OF
TABLETS
4 MAJOR TYPES
ORALLY
INGESTED
TABLETS
TABETS FOR
ORAL
CAVITIES
TABLETS
GIVEN
THROUGH
OTHER
ROUTES
TABLETS TO
PREPARE
SOLUTIONS

ORALLY INGESTED TABLETS
Compressed
tablets
Multiple
Compressed Tablets
Enteric Coated
Tablets
Sugar Coated
Tablets
Film Coated Tablets
Chewable Tablets

Majority of the tablets are ingested orally. These
tablets are swallowed intact along with a sufficient
quantity of water.
Compressed tablets – prepared by compression f
powdered crystalline or granular materials, by the
application of high pressures using punches and die. They
do not contain any special coating. Here rapid
disintegration occurs which releases the drug rapidly.
Multi - compressed tablets – composed of 2-3 layers.
Prepared by introducing the fill material to more than one
compression cycle. Multi compression is done in cases
where the ingredients are physically or chemically
incompatible or when a prolonged action is required. They
are further classified into 3 : - compression coated tablets
:- layered tablets
:- inlay tablets

Compression coated tablets – consists of 2 parts –
internal core (the tablet) and surrounding coat.
These tablets are prepared by filling coat material to
half, core tablet is mechanically transferred, again
remaining space is filled with coat material, and
finally compression force is applied.
Inlay tablets – tablet core is not completed
surrounded by the coating, top surface is completely
exposed. Prepared by filling the die with coating
material and mechanically placing the core in the
die, the compressed. Coat is displaced to form the
sides.
Layered tablets - consists of 2 -3 ingredients in
layers. Preferred when 2 or more ingredients have to
be administered simultaneously.

Compression coated tablets
Inlay tablets
Layered tablets

Enteric tablets – formulated to prevent drug
release in the stomach. Such an enteric coating is
preferred when the drug gets inactivated or
destroyed by gastric pH, or when drug is irritating to
the gastric mucosa. Enteric coat is insoluble in the
acidic pH and soluble in the alkaline pH. Such
tablets are also meant for delayed release.
Enteric coating materials – polymers like Cellulose
acetate phthalate, hydroxypropylmethylcellulose.
Sugar coated tablets – contain concentrated sugar
solution coating. Used to improve patients
compliance, increase physical appearance, mask
unpleasant taste, increase the stability or modify the
release of the drug.

Film coated tablets – are tablets coated with a
thin layer of polymer material or a mixture of
polymer materials. The coating is designed to
break the core tablet at the desired location in the
GIT. Film coating also protects the tablet from
atmospheric effects.
Chewable tablets – are chewed prior to
swallowing, useful for children or adults who
have difficulty with swallowing the tablet intact.
Substances like mannitol, dextrose are used in
the preparation along with the active ingredient.
These tablets do not require any disintegrating
agents. They should also have an acceptable taste
and flavour.

TABLETS FOR ORAL CAVITIES
Buccal and
Sublingual Tablets
Lozenges and
Troches
Dental Cones

Oral cavity includes lips, cheeks, teeth, gums,
floor of the mouth, bony roof of the mouth,
and two thirds of the tongue.

Buccal and Sublingual tablets – small and flat
oval tablets.
Sublingual administration – placing drug under
the tongue to dissolve and absorb into the blood.
Buccal administration – placing a drug between
gums and cheek to dissolve and absorb into
blood
Lozenges and troches– disc shaped with
medicinal agents incorporated in flavoured hard
candy or sugar base. Intended to be dissolved
slowly in the oral cavity
Dental cones - are compressed tablets which
are placed in the empty sockets after tooth

Buccal
Tablets
Sublingua
l Tablets
Dental
Cones

TABLETS GIVEN BY OTHER ROUTES
Implantation
Tablets
Vaginal tablets

Implants – long acting sterile tablets which are
designed to provide continuous release of drugs
for the months or a year. Placed under the skin or
inserted subcutaneously by means of minor
surgical operation. Implants must be sterile.
Packed individually in sterile conditions.
Contains rate controlling excipients. Mainly
employed to administer hormones.
Vaginal Tablets – uncoated bullet shaped or
ovoid tablets. They are designed to dissolve
slowly in the vaginal cavity. Used to release
medicaments to provide local pharmacological
effect and for systematic absorption.

TABLETS TO PREPARE SOLUTIONS
Effervescent
Tablets
Hypodermic
Tablets
Dispensing
tablets
Tablet Triturates /
Moulded Tablets

Effervescent tablets – uncoated tablets that
contain the following – active ingredient,
organic acids (eg. tartaric acid), and sodium
bicarbonate. When dropped into water, tablet
reacts with water releasing carbon dioxide,
producing effervescence leading to
disintegration.
Dispensing Tablets – contain large amount
of highly potent active pharmaceutical
ingredients. They should be added to given
volume of water. Great care should be taken
in packaging and labelling. These tablets are
readily dispensed into liquids.

Hypodermic tablets – soft readily
soluble tablets. Tablets composed with
drugs that are water soluble and they are
dissolved in sterile water or water for
injection, and administered via
parenteral routes.
Tablet triturates– small cylindrical
molded or compressed tablets. They
usually contain a potent drug mixed with
excipients like lactose, sucrose or any
other suitable diluent. Prepared in
special molds

Hypodermic Tablets Mold for Tablet Triturates
Effervescent
Tablets

EXCIPIENTS
Pharmaceutical Excipients :- are substances
other than the pharmacologically active drug
or pro -drug which are included in the
manufacturing process or are contained in a
finished pharmaceutical dosage form.
Helps the drug to exert its action at the required
location.
Also it keeps the drug from being released early.
Some may help in protecting the product
stability, taste better, look better, improve
patients compliance and also to break into
smaller pieces.

PRESERVATIVE
S
DILUENTS
BINDERS
LUBRICANT
S
DISNTEGRANT
S
COLOURANTS
FLAVOURS &
SWEETNERS
GLIDANTS
ANTI-
ADHESIVES
ADSORBANT
S
DISSOLUTION
RETARDANTS
DISSOLUTION
ENHANCERS
BUFFERS
ANTI-
OXIDANTS
CHELATING
AGENTS
TYPES OF
EXCIPIENTS

DILUENTS
Also known as fillers or bulking agents.
Use for making up of required bulk for a tablet.
Mostly used when dose of drug is too small to
formulate as a tablet. If the dose is high, bulking
agents are avoided.
Properties of an ideal diluent :- physiologically
inert, non toxic, physically and chemically stable,
easily available, free from microbial contamination,
and does not affect the bioavailability of drug.
Diluents can be of the following types:- lactose,
spray dried lactose, mannitol, dextrose, starch,
sorbitol, sucrose and microcrystalline cellulose.

Lactose – Most widely used Diluent. Available
in the hydrous and anydrous form. Preferred
because of pleasant taste, readily dissolvable in
water, low cost and less disintegration time. One
disadvantage is that it undergoes discolouration
when in contact with amine drugs
Spray dried lactose – can be used for direct
compression due to its cohesive nature and good
flow characteristics. In presence of moisture,
they may undergo darkening.
Mannitol – widely used as a diluent in
chewable tablet. It is non-hygroscopic and non-
carcinogenic. But mannitol is expensive.

Dextrose – Available in the hydrous and
anhydrous form. When combined in a certain
amount with spray dried lactose, darkening of
spray dried lactose can be avoided.
Starch – very occasionally used diluent for
tablet manufacturing. USP grade of starch can
be used due to its free flowing nature and
direct compressibility.
Sucrose – suitable for direct compression.
Microcrystalline cellulose – two main
grades are available but they are expensive,
so used in combination with other diluents.

BINDERS
One of the most important excipient in tablet
formulation.
Also called as Adhesives.
When mixed with powders, they are used to produce
granules.
Enhance the free flowing capacity of granules of
desired sized and hardness.
Selection of binder depends on the type of tablet.
For eg. lozenges require more amount of binder
whereas tablets require less.
Binders can be of the following types:- gum
acacia, tragacanth, starch paste, sucrose solution,
polyvinylpyrolidine, gelatin, celluose derivatives –
HPMC, HEC.

Gum acacia and tragacanth – used alone in a
concentration of 10-25% or in combination.
Gelatine – should be prepared fresh and added in
warm condition to avoid solidification.
Starch paste – is prepared by dispensing starch into
cold purified water, warming the mixture by
continuous stirring until a translucent paste is formed.
Sucrose solution – is used a wet binder which is
cheap, produces hard but brittle granules. Major
disadvantage is the susceptibility to microbial
contamination.
PVP – used in an aqueous or alcoholic solution.
Suitable for moisture sensitive drugs.
Cellulose derivatives – natural polymer as binder.

LUBRICANTS
Are intended to reduce the friction between the
walls of the tablet and walls of the die cavity during
the ejection of tablet. Concentration and time of
mixing of a lubricant should be optimised. If the
concentration is more, mechanical strength of the
tablet is reduced.
LUBRICANTS
SOLUBLE
LUBRICANTS
INSOLUBLE
LUBRICANTS

Insoluble Lubricants – act by inter-crossing the
intermediate layer between the tablet material and the
die cavity. Such lubricants are intended to act on the
tablet surface or on the tablet coating surface, so
added in the last stage before compression.
E.g – Calcium or Magnesium stearate, light mineral
oil, paraffins etc.
Optimum concentration – 1-4%
Soluble Lubricants – not effective as the insoluble
lubricant.
E.g – adipic acid, magnesium lauryl sulphate,
sodium lauryl sulphate, polyethylene glycol 4000,
6000, 8000.

DISINTEGRANTS
Intended to break up a tablet to smaller pieces
upon administration, when it comes in contact
with the gastro intestinal tract.
Tablet disintegration is important for the further
dissolution of the drug and attaining the drug
bioavailability.
Mainly used disintegrants – starch, cellulose and
cellulose derivatives. Starch is mainly used due to
its cheaper cost, ease of availability, and
compatibility with drugs.
Optimum concentration – 5-20%

MECHANISM OF DISINTEGRATION
 Water uptake through pores
 Acts by swelling of disintegrants
 Acts by producing gas
 Enzymatic action

Water uptake through pores
 Water uptake through the pores due to
capillary action leads to disintegration.
 Hence, hydrophobicity can be a
disadvantage for disintegrants using this
mechanism.
 Maintenance of the porous structure of
the drug is also an important factor.
 E.g – Starch and Microcrystalline
cellulose

Swelling of Disintegrants
 One general problem of such disintegrants is
its thickness or forming of a gelatinous mass
on contact with water.
 E.g – Acacia and Tragacanth
 Optimised concentration should be used,
otherwise it may lead to sticking of the
powder.
Disintegrants that work due to the porous
structure and by swelling are called
Superdisintegrants
• E.g – sodium starch glycolate, sodium
glycine carbonate, insoluble cationic
exchange resins

Acts by producing gas
 Used when extra rapid disintegration is
required.
 Main disadvantage is its stability. When in
contact with the slight excess of moisture,
it can initiate the reaction.
 Stringent control on the environment is
required for such type of disintegrants.
Enzymatic action
 Enzymes are included to act in the
presence of water.
 E. g – Amylase.

FLAVOURS & SWEETENERS
Flavours and sweeteners are added in the
formulation to mask the unpleasant taste. Added in
the concentration – 0.001 – 0.1 %
Dissolved in organic solvents and then the solution
is sprayed on the granules just before the step of
compression.
Natural sweeteners :- sugar, mannitol, lactose,
sucrose
Artificial sweeteners :- saccharin, cyclamate,
aspartame

COLOURANTS
Added to the preparation to make the tablet more
aesthetic.
Also used to identify the product.
All colourants used should be approved and certified
by the Food and Drug Administration.
Colours are available in two forms : - lakes and dyes
E.g – Eosin Y, Sunset yellow FCF, Yellow orange,
Blue green, Burnt sugar.

ANTI - ADHESIVES
Prevents sticking of the tablet material to the
face of the punch or on to the die cavity.
All lubricants can be used as anti-adhesives
except for water soluble lubricants.
E.g – Talc, Magnesium stearate, Colloidal
silica

GLIDANTS
Used to facilitate or promote flow of granules
from hopper to die cavity by reducing friction
between the particles
E.g – Talc
Optimum concentration – 4-5%
Lubricants,
Glidants
and Anti –
Adhesives
Together
called as
Antifrictional
Agents

ADSORBANTS
Usually agents that can retain large quantities of
liquid
E.g. – anhydrous calcium phosphate, magnesium
carbonate, kaolin
BUFFERS
Added to maintain a required pH.
E.g – sodium bicarbonate, sodium citrate
ANTIOXIDANTS
Added to protect drug from oxidation
Anti-oxidants undergo oxidation instead of the
drug
E.g – ascorbic acid, sodium bisulphite

CHELATING AGENTS
Tend to form complexes with trace amount of
heavy metal ions that can initiate oxidation by
theor catalytic activity
E.g. – ethylenediamine tetraacetic acid {EDTA},
citric acid
PRESERVATIVES
Prevents the growth of microorganism that can
lead to contamination
E.g – parabens like methyl paraben, propyl
paraben

DISSOLUTION ENHANCERS
Alter the molecular forces between the
ingredients to enhance the dissolution process
leading to faster therapeutic action
E.g. – surfactants
DISSOLUTION RETARDANTS
Incorporated into tablets that are intended for
controlled or delayed release.
E.g – waxy materials like stearic acid and their
esters

TABLETS GRANULATION
Tablet Granulation:- is the process in which
small powder particles adhere together by
forming bonds between them, resulting in the
formation of large aggregates called granules.
The bonds are formed either by compression
or by using binding agents.

IMPORTANCE OF TABLET GRANULATION
Even though powders are present, granules are
prepared due to the following reasons :-
To avoid particle separation in powders, due to their
different size, shape and densities.
Enhance the flow property. Higher flow ability gives
better filling of dies or containers.
Granules have higher porosity.
Improves compressibility of powders.
Materials that are hygroscopic may adhere and form
a cake if stored as a powder.
Granulation of toxic materials will reduce the hazard
of generation of toxic dust, which may arise during
the handling of powders.

GRANULATION METHODS
Granules are used in the manufacturing of
Tablets and Pellets.
GRANULATION METHODS
DIRECT
COMPRESSION
WET
GRANULATION
DRY
GRANULATION

DIRECT COMPRESSION
Direct compression is a dry process where in the
powdered material is compressed directly into the
tablets without the physical nature of the powder being
modified
Direct Compression involves the following steps:-
Weigh and grind the ingredients (active ingredients
and excipients).
Mixing of active ingredients with powdered excipients
including the lubricants and glidants.
Compression of mixed powders in a tablet press.
Diluent – spray dried lactose, mannitol
Disintegrants – talc
Lubricants – magnesium stearate
Glidants – talc, colloidal silica

Advantages – fewer processing steps, less
equipment, less expensive, no involvement of
moisture and heat, faster dissolution rate, chance
of transfer losses, and lesser equipment
contamination.
Disadvantages – selection of excipients is
highly restricted due to less inherent binding
property in most of the excipients, low dose of
drugs will not be uniformly mixed, excipients for
direct compression are expensive and they also
have a problem of interaction with drug
substances.

WET GRANULATION
Wet or Moist granulation is the most
conventional, versatile, and widely used techniques for
the manufacture of compressed tablets.
This technique involves the usage of liquid to form
compact masses.
Wet granulation involves the following steps:-
Weigh, sift and mix of drug substance and excipients
excluding lubricants in an appropriate mixer to get
uniform powder mix.
A damp mass is prepared from the powder mix using a
binder solution. Insufficient binder causes poor
adhesion leading to soft tablets. Excessive binder
solution yields hard tablets with slower disintegration
rate.

Wet granules are dried in an hot air oven at 60℃. The
drying temperature and drying time are carefully
observed.
Dried granules are passed through Sieve 20 to get
uniform size granules.
Appropriate amount of lubricants is mixed with
granules. The remaining amount of disintegrants are
also added at this stage.
Mixed granules are compressed in a single or multi-
punch station tablet press fitted with appropriate
punches and dies.

Advantages – produce more spherical granules,
have better flow property, useful for low
compressibility drugs, ensures better content
uniformity in case of low dose drugs, improved
compressibility, suitable for hydrophilic drugs.
Disadvantages – several steps are involved,
time, labour, energy, equipment and space
required for the process is more, not suitable for
hydrophobic, thermolabile and moisture
sensitive materials, water used as solvent can
affect the drugs stability causing hydrolysis,
drying time is longer, increased length of process
.

DRY GRANULATION
Dry or Double compression is used to form
granules without using a liquid solution because the
product to be granulated may be sensitive to moisture
and heat.
The techniques of dry granulation of powdered
material can be accomplished by two methods :-
1. Slugging – formation of extra large tablets first,
then broken into granules, which are again
recompressed.
2. Roller compaction method – achieved by feeding
powder through a set of directly opposed counter
rotating rollers.

Dry granulation involves the following steps:-
Appropriate quantities of ingredients and excipients are
weighed on an analytical balance.
Ingredients are mixed in a powder mixer until a uniform
powder mix is achieved. The half quantity of lubricant is
added at this stage to enhance powder flow and to prevent
sticking of powder to die.
Mixed ingredients are compressed into flat large tablets
called slug. This is called pre-compression or slugging.
Slugs are broken into smaller pieces using an appropriate
miller. Milled slugs are sieved to produce uniform granules.
After sieving, remaining lubricants and excipients are
incorporated into granules and mixed to form a uniform
blend.
Mixed uniform blend of granules are compressed into
tablet using the tablet press.

Advantages – requires less equipment and
minimum floor space, suitable for moisture and
heat sensitive materials, no alteration in drug
morphology during formulation, shows better
disintegration as dry binder has lesser adhesive
effect.
Disadvantages – process generates dust which
can cause cross contamination, separation of
components may occur after mixing, flowability
of powder decreases .

TABLET COMPRESSION
MACHINES
Dried granules are compressed into tablet
using machines known as Tablet Compression
machines or Tablet Press.
TABLET COMPRESSION MACHINES
SINGLE PUNCH
TABLET MACHINE
MULTI STATION
ROTARY PRESS
DRY COTA TABLET
MACHINE

Tablet presses are designed with following
basic components.
Hopper – holds an feed granules to be
compressed.
Dies - define size and shape of tablet
Punches – compresses granules within the
dies.
Cam Tracts – guides the movement of
punches
Feeding Mechanism – moving mechanism
of the granules from the hopper to the dies.

HOPPER
PUNCHES & DIES
CAM
TRACT

SINGLE PUNCH TABLET MACHINE
Also called as ECCENTRIC PRESS.
Ideal for Small Scale Productions. This
tablet press includes a Die and a pair of
Upper and Lower Punch, along with the
basic components. Also the machine has two
more components :-
Capacity Regulator – adjusts lower punch
to allow the required quantity of granules by
the die.
Ejection Regulator – facilitates ejection of
tablet from die cavity after compression.

WORKING OF SINGLE PUNCH STATION
The upper punch moves up and lower punch moves
down to create a cavity in the die.
Feed or granules from the hopper fall into the dies.
Upper punch moves down - compresses the
granules into tablets
Upper punch moves up, lower punch also moves up
– eject the compressed tablet.
Whole process repeats again and again, until
granules finishes.
Output – 200 tablets per minute
Uses high pressure to compress tablet to reduce
weight variation between tablets.

MULTI STATION ROTARY PRESS
Multistation rotary presses are termed as
“rotary” because the head that holds the die, upper
and lower punches in place – Rotates.
As the head rotates, the punches are guided up
and down by fixed cam tracts.
The portion of the head that hold the upper
punches are called upper turrets, and the portion that
hold the lower punches are called lower turrets. The
portion holding the dies are called die table.
Along with the basic components, additional
components are,
Ejection cam – facilitates ejection of tablet from die
Take off blades – helps to push tablet to a discharge
chute, which is collected in a container.

WORKING OF MULTISTATION ROTARY
PRESS
The powder or granules are placed in the hopper.
Material is fed into several dies simultaneously.
Machine removes excess of powder to avoid any
form of inconsistencies.
Desired volume and weight of powder is
compressed to tablets.
Upper and lower punch exert a predetermined
amount of pressure that compresses the tablet.
As the head revolves, dies get filled with granules
flowing from the hopper.
Granules are compressed when the upper and
lower punch comes close together.

The upper cam pull the upper punches back to the
initial position and the lower punches are lifted up
to eject processed tablets out of the die cavity.
Scraper will remove the tablet from compression
machine.
This is then considered, as the end of one
compression cycle of the tablet compression
machine
Output – 1200 tablets / minute.
Used for large scale production.

DRY COTA TABLET MACHINE
Here, two rotary machines work
simultaneously, therefore, core tablet is
prepared in one machine, and then
transferred to the another machine for
compress coating.
Preferred for multicompressed, multicoloured
and press coated tablets
Allow manufacture to manufacture a wide
variety of tablet shapes.

EQUIPMENT TOOLING
Equipment tooling:- The size and the shape of
a tablet, and certain identification markings
are determined by the equipment tooling or
compression machine tooling.
Each tooling set consists of die and upper and
lower punches.
Tooling must meet the requirements to satisfy
the needs of dosage uniformity, product
efficiency and aesthetic appearance.

Basically, there are two types of equipment
tooling or compression machine tooling.
EQUIPMENT TOOLING
D TOOLING BB TOOLING

PARAMETERS D TOOLING BB TOOLING
Compression
force exerted by
the machine on
the tools
10 tonnes 6.5 tonnes
Barrel diameter
of the Punch
1 inch 0.75 inch
Head diameter of
the Punch
1.25 inch 1 inch
Length of the
Punch
5.25 inch 5.25 inch
Die Diameter 0.945 inch 1.18 inch

Several types of steel are normally used for the
manufacture of compression machine tools. Steel
differs in toughness to withstand the compressing forces
and wear resistance. Therefore, selection of the steel
must be based on experience and accumulated history
of the product to be manufactured.
Improper storage and handling can readily result
in damage and lead to the complete replacement of
the whole set of punches and dies.
Punch tips are delicate and susceptible to damage,
if they come in contact with each other or with the
dies, or due to improper handling while insertion
and removal of the punches and dies.
To avoid tooling damage, calculate the load or
pressure to be applied before the production starts.

COMPRESSION &
PROCESSING PROBLEMS
An ideal tablet should be free from any
visual or functional defect. Number of problems
can be encountered during the tablet manufacture
process.
Visual defects :- due to inadequate fines or
moisture in granules or faulty machine settings.
They can be further due to the following factors
:- formulation design, tabletting process, machine
related, or others.
Functional defects :- due to a faulty
formulation calculation.

VISUAL
DEFECTS
PROCESS
RELATED
CAPPING &
LAMINATION
CHIPPING &
CRACKING
FORMULATION
RELATED
PICKING & STICKING
WEIGHT &
HARDNESS
VARIATION
MOTTLING
MACHINE
RELATED
DOUBLE
IMPRESSION

1. CAPPING & LAMINATION
1. Capping – partial or complete separation of top or
bottom crown of the tablet from the main body of
the tablet
2. Lamination – separation of the tablet into 2 or
more distinct layers.
Capping & lamination occurs due to the following
reasons:-
 Presence of excess fine powders will lead to
entrapment of air in the tablet during compression
. This air has a tendency to come out leading to
cappig and lamination. Quantity of fine
incorporated should be optimised to correct the
problem

Worn out punches and dies also cause capping and
lamination. Hence, replacement of the punches are
required. Chromium plated dies can be used to correct
the problem.
High pressure also an be used, which can be
optimised before the production starts.
Insufficient or improper lubricant can cause this
problem, hence the amount of lubricant used can be
optimised or the type of lubricant can be changed.
Addition of oily or waxy materials can cause
capping and lamination, that can be corrected by the
usage of adsorbents or absorbents.
Over drying of granules are also a major reason for
capping and lamination to occur. This can be overcome
by the addition of optimum level of moisture.

2. PICKING
Picking – material gets off from the tablet
surface and adheres to the face of the
punch.
Reasons :-
 When punches have letters with sharp edges like
A, B, M, W etc.
 When granules are improperly dried.
 When materials have low melting point.
Corrections :-
 punches that have sharp edged letters can be
corrected by modifying the design of letters.
 When using low melting point materials, punches
should be polished with colloidal silica

3. STICKING
Sticking – material gets off from the
tablet surface and adheres to the
die wall.
Reasons :-
 Presence of excess moisture.
 Improper lubrication of granules.
 Fast compression process.
Corrections :-
 Proper drying of granules.
 The amount of lubricant used can
be optimised or the type of
lubricant can be changed.
 Speed of the compression process
should be optimised
 Dies should be polished with
colloidal silica

4. MOTTLING
Mottling :- is a defect that occurs with
coloured tablets.
 Mottling occurs due to the uneven
distribution of the colour on the surface
of the coloured tablets.
Reasons :-
 Migration of the dye on the tablet
surface during the process of drying
 Decomposition of active ingredient or
excipients improper mixing of colour
binder solution
Corrections :-
 Change the solvent system and decrease
of temperature while drying.
 Incorporating dry colour excipients and
fine powdered adhesives during mixing
step of ingredients. Then the granulating
liquid is added to prepare granules.

5. CHIPPING
Chipping :- is a defect where the film on
the edges of the tablet is chipped or
dented.
Reasons :-
 Dry granules
 Addition of large amount of binder
 Worn out edges of the punch
Corrections :-
 Addition of hygroscopic substances to
moisten the granules.
 Polishing of edges of punch.
 Optimisation of the amount of binder.

6. CRACKING
Cracking :- is a defect where upper and
lower central surface of tablets gets
cracked.
Reasons :-
 Dry granules
 Size of granules are too large, air can
get entrapped between the cavities,
and during compression cracking
occurs.
 Deep concave shaped punches
Corrections :-
 Addition of right amount of binder
moistening the granules.
 Reduce granules size or add fines.

7. DOUBLE IMPRESSION
Double impression – is a defect where the
shape of the monogram or other
engravings appears stamped twice on the
tablet.
Reasons :-
 Due to the free rotation of the lower punch. The
lower punch moves slightly upward before the
ejection of a tablet and makes new impression on
the bottom of the tablet
Corrections :-
 Control the free rotation of any punches

8. WEIGHT VARIATION
Weight variation– occurs when tablets
compressed do not have uniform
weight .
Reasons :-
 When granules are not in uniform size.
This changes the filling of granules in
the die. Large size or too small size
granules changes can hence cause
weight variation.
 Poor flow of granules from the hopper
to the die. Rat holing, where the
powder gets deposited over the inner
walls of the hopper, this obstructs the
flow of powder from the hopper to die.
Corrections :-
 Addition of vibrator to the hopper to
improve the flow of powder.

9. HARDNESS VARIATION
Hardness variation– occurs when tablets
compressed do not have uniform
hardness.
Reasons :-
 No uniform weight
 Incorrect space between the upper and lower
punch at the time of compression
Corrections :-
 Maintain the weight of the tablet.
 Optimum gap between the upper and lower punch
should be maintained.

CONTENTS
 Introduction
 Types of Tablet Coating
 Coating Materials
 Coating Composition
 Coating Equipments
 Tablet Coating Defects

INTRODUCTION
Tablet Coating :- is the last critical step in the
Tablet Production Cycle. Tablet coating is the
process in which the tablet surfaces become
covered with a tacky polymeric film to achieve
specific benefits. The successful application of
coating to tablet provides the visual
characteristics for the product, thus the
quality of the product may be judged on this
final production step.

Need of Tablet Coating
This additional step of tablet coating in the tablet
manufacturing process, increases the cost of the product.
Therefore, the decision to coat a tablet can be based on the
following reasons :-
Mask unpleasant taste, odour, or colour of a drug.
Provide physical and chemical protection for the drug.
Improve pharmaceutical elegance by use of special
colours and contrasting printing.
Control the release of the drug from the tablet.
Protect the drug from gastric environment of the stomach
with an acid resistant enteric coating.
Incorporate another drug in the coating to avoid chemical
incompatibilities or to provide sequential drug release.

TYPES OF TABLET COATING
6 MAJOR TYPES
SUGAR
COATING
FILM
COATING
ENTERIC
COATING
VACUUM FILM
COATING
ELECTROSTATI
C COATING DIP COATING

SUGAR COATING
Sugar coating :- is the process of depositing
layer that an be either coloured or uncoloured to the
tablets. This process is a step wise process. The
operator determines :-
the quantity of the coating solution to add,
the method and the rate of pouring of coating
solution,
when to apply the dry air and
how long or how fast the tablets should be tumbled
in the coating pan.

The steps involved in sugar coating are :-
Water
Proofing /
Seal
Coating
Sub
Coating
Syrup
Coating
Colouring Polishing

1. WATER PROOFING / SEAL COATING
Seal Coating :- done to provide moisture
barrier to the core tablet and harden the tablet
surface.
Helps to maintain physical and chemical
stability of the finished product.
Materials used in Seal coating :- Shellac ,
Zein
Shellac :- effective sealant but it may slow
down the disintegration & dissolution time
which affects the therapeutic release.
Zein :- an alcohol soluble protein derivative
from corn is another effective sealant.

Tablets are placed in a coating pan made of stainless
steel
Rotate the coating pan at the speed of 10rpm with
supply of air at 30℃.
Three applications of sealing solution {800ml /
application} are given
15-20 mints are given for proper drying after each
application.
Talc is added so that tablets do not stick to each other

2. SUB COATING
Sub Coating :- applied to round the edges and
build up the tablet size. Two methods are used for
this sub coating.
Applying a sticky binder solution to the tablets
followed by dusting of sub coating powder and
then drying. This is repeated until the desired size
is achieved. Sub coating powders include :-
calcium carbonate, powdered sucrose,
powdered dry gum acacia.
Another method, is the spraying process, where
a sub coating powder suspension containing both
the binder and the insoluble powder is sprayed
intermittently on the tablet bed

Turn heat and inlet air off. Use only exhaust system
Rotate the coating pan at the speed of 10rpm
Use 1.5 litres of sub coating solution and apply 3-9 coats to
the tablets. Thickness is checked volumetrically. 15-20 mints
are given for proper drying after each application.
Apply sub coating powder until tablets roll freely and show
no signs of stickiness.
After last coat, jog the pans periodically for at least 2-4 hours
to ensure dryness.

3. SYRUP COATING or SMOOTH COATING
Syrup coating or Smooth Coating :- done to
cover and fill the imperfections in the tablet
surface caused by the sub coating step, so as to
increase the tablet dimension to a predetermined
level.
Several coats of simple syrup solution (60-
70%) are applied.
Syrup solution contains pigments, starch, gelatin,
or acacia.
Syrup solutions are also called grossing syrups.

Remove excess dust in the coating pan. Turn on the exhaust
inlet air with a temperature of 45-48℃.
Apply 5-15 coats of grossing syrup. Since this solution dries off
quickly, uniform rapid distribution is provided
The process is done until specific tablet volume is required, and
then turn off the heat.

4. COLOURING
Colouring :- gives colour an finished size of the
tablet.
A thin sucrose solution containing the requisite
colouring materials is used for the process.
Water soluble dyes or water insoluble pigments
can be used.
Water insoluble dyes are preferred over water
soluble dyes as water soluble dyes may cause
mottling.

Turn off the heat with no supply of air,
3-4 coats of regular coloured syrup is applied rapidly.
The last coat should be syrup solution without colour and allow
to dry overnight.

5. POLISHING
Polishing :- Tablets after colouring, they are
polished to give desired luster to the tablet.
Polished by carefully applying, powdered wax
{ beeswax or carnauba} or warm solutions of
these waxes in naphtha or suitable volatile
solvents.

Cleaned canvas lined coating pans are used. Air is supplied
with exhaust air.
Turn off heat and rotate coating pan at speed of 12rpm.
Apply 3 - 4 coats of warm polishing solution, approximately
300ml per application. Let the solvent evaporate between each
coats

FILM COATING
Film coating :- is the process of placing a thin,
skin tight coating of plastic like material or polymer
over the compressed tablet. Film coating solutions can
be non – aqueous or aqueous. Volatility of the solvent
enables the film to adhere quickly to the surface of
tablets.

Ideal Characteristics of a Film Coating
Material
Adequate solubility in coating solvent and in the
GI fluid.
Stability in presence of heat, light, moisture, air,
etc.
Compatibility with addictives present, non –
toxic, inert, resistant to cracking, withstand
normal handling.
Compatibility to obtain a elegant product.
Ease of printing procedure on high speed
equipment.

Film Coating Materials
Film formers
Alloying substance
Solvent system
Plasticizer
Opaquant extenders
Colourants
Glossants
Anti – Oxidants
Flavours & Sweetners
Surfactants
Anti – Microbials

1. FILM FORMERS
oCapable of producing smooth thin film
reproducible under conventional coating
conditions and applicable to variety of tablet
shapes.
oPolymers are mainly used as film formers.
oE.g – cellulose acetate phthallate, hydroxy
propyl methyl cellulose, sodium carboxy
methyl cellulose.

2. ALLOYING SUBSTANCE
oProvides water solubility or permeability to the
film to ensure penetration by body fluids and
therapeutic availability of the drug.
oE.g – polyethylene glycol

3. SOLVENT SYSTEM
oIs mainly used for the dissolving of solvent and
to allow the spread of other components over the
tablets while allowing rapid evaporation to permit
speedy operation.
oE.g – ethanol, methanol, chlorinated
hydrocarbons, methylene chloride.

4. PLASTICIZER
oGives elasticity and flexibility to the coat
material that increases the durability. Plasticizers
act by breaking down the polymer – polymer bond
and reducing the films brittleness.
oE.g – castor oil, propylene glycol, polyethylene
glycol.

5. OPAQUANT EXTENDERS
oAdded to give more pastel colours and enhance
film coverage.
oE.g – titanium dioxide, talc, magnesium
carbonate.
6. COLOURANTS
oAdded to enhance visual appeal of the product
and identify the product.
oE.g – sunset yellow, tartrazine, erythrosine.

7. GLOSSANTS
oAdded to give luster to the tablet without
polishing.
oE.g – beeswax.
8. ANTI - OXIDANTS
oAdded to stabilize a dye system.
oE.g – oximes, phenols.

9. FLAVOURS & SWEETNERS
oAdded to mask unpleasant taste and odour.
oE.g – aspartame, water soluble pineapple
flavour.
10. SURFACTANTS
oAdded to solubilise insoluble ingredients in the
coating.
oE.g – spans and tweens.
11. ANTI - MICROBIALS
oAdded to prevent microbial growth in coating
composition.
oE.g – alkylisothiazolinone, carbamates.

ENTERIC COATING
Enteric coating :- is the process of coating done to
the tablet to protect from the acidity of stomach and
usually disintegrate the tablet in the intestine.
Reasons of Enteric Coating :-
Protect acid labile drugs from GI fluid.
Prevent gastric distress or nausea due to irritation
from a drug.
Deliver drugs intended for local action in the
intestines.
Deliver drugs that are optimised to absorb in the
small intestine.
Provide delayed release

Ideal Characteristics of a Enteric Coating
Material
Resistant to gastric fluids
Ready susceptibility or permeability to intestinal
fluids.
Compatibility with coating solutions.
Formation of continuous film
Non toxicity, low cost, ease of application
Enteric coating materials :- cellulose acid phtahllate,
shellac and its derivatives

ELECTROSTATIC COATING
Electrostatic coating :- used to apply coat
conductive substances.
Coating material contains conductive ionic species
of opposite charge is sprayed on to the charged
substrate.

DIP COATING
Dip coating :- coating is applied to the tablet cores
by dipping them into the coating solution.
Wet tablets are dried in an conventional manner in
coating pans

VACUUM FILM COATING
Vacuum Film Coating :- is a coating procedure that
employs a specially designed baffled pans.
Pan is water jacketed.
Sealed to achieve a vacuum system.
Tablets are placed in the sealed pan.
Coating solution is then applied to tablets with an
airless spray system.

The coating materials is a physical deposition
of the material on the tablet substrate, or they form a
continuous film with a wide variety of properties
depending on the composition of the coating
formulations.
Examples of physical deposition of the coating
materials are the techniques of sugar, shellac, wax or
polymer coatings
TABLET COATING MATERIALS

Coating Materials
1. Hydroxypropyl methylcellulose USP {HPMC}
2. Methyl hydroxyethylcellulose {MHEC}
3. Hydroxypropylcellulose {HPC}
4. Ethylcellulose {EC}
5. Sodium carboxymethylcellulose {Na CMC}
6. Povidone USP
7. Polyethylene glycol {PEG}
8. Acrylate polymers
9. Polyvinyl acetate phthalate {PVAP}
10. Cellulose acetate phthalate {CAP}
11. HPMC Phthalate

1. HYDROXYPROPYL
METHYLCELLULOSE USP
oPrepared by reacting alkali treated cellulose with
methyl chloride to introduce methoxy groups and
then react with propylene glycol ether groups
oAvailable in different viscosity grades
oSoluble in GI fluid and other solvents.
oCauses no change in disintegration and
bioavailability.
oStable in presence of heat, light, moisture or air
oEasily able to incorporate or other addictives.

2. METHYL HYDROXYETHYLCELLULOSE
oPrepared by reacting alkali treated cellulose with
methyl chloride to introduce methoxy groups and
then react with ethylene oxide.
oAvailable in different grades
oStructural similarity of MHEC with that of
HPMC, shows that MHEC shares the same
properties of HPMC.

3. HYDROXY PROPYLCELLULOSE
oPrepared by reacting cellulose with sodium
hydroxide and then react with propylene oxide at
an elevated temperature and pressure.
oYield flexible films
oSoluble in water below 40℃, GI fluid, polar
organic solvents.
oUsually used in combination with other polymers

4. ETHYLCELLULOSE
oPrepared by reacting ethyl chloride or ethyl
sulfate with cellulose dissolved in sodium
hydroxide.
oInsoluble in water below 40℃ & GI fluid. Hence,
used in combination with a water soluble
addictives.
oUnplasticized EC films are brittle and require
film modifiers to obtain an acceptable film.

5. SODIUM CARBOXY
METHYLCELLULOSE
oSodium salt of carboxymethylcellulose
oPrepared by reacting soda cellulose with sodium
salt of monochloroacetic acid.
oInsoluble in organic solvents but soluble in water
to form colloidal solutions.
oFilms are brittle but adhere well to the tablets.

6. POVIDONE USP
oSynthetic polymer consisting of linear 1-vinyl 2-
pyrrolidinone groups.
oAvailable in 4 different viscosity grades
identified with a “K” value – povidone K 15, K30,
K60, and K90
oK30 is the most used povidone grade in tablet
coating.

7. POLYETHYLENE GLYCOLS
oManufactured by the reaction of ethylene glycol
with ethylene oxide in presence of sodium
hydroxide at an elevated temperature and
pressure.
oPEG of lower molecular weight are liquid at
room temperature and used as plasticizer.
oPEG of higher molecular weight are white, waxy
solids at room temperature and used as a coating
material.

8. ACRYLATE POLYMERS
oAre set of polymers commercially under the
trademark EUDRAGIT.
oEudragit are available in different forms.
oEUDRAGIT E :- cationic polymer, which is the
only form of eudragit which is soluble in GI fluid.
oEUDRAGIT RL & RS :- copolymers available
only as organic solutions and solid materials.
These are mainly used as coating material in
delayed release tablets.
oEUDRAGIT L & S :- polymers that are mainly
used in coating of enteric coated tablets. They are
soluble only in pH 6 & pH 7 respectively.

9. CELLULOSE ACETATE PHTHALATE
oWidely used as enteric coating material.
oDissolves only in pH > 6
oHygroscopic, relatively permeable to water and
GI fluids
oProduces brittle films, hence, combined with
hydrophobic film forming materials to achieve a
better enteric film.

10. POLYVINYL ACETATE PHTHALATE
oManufactured by esterification of partially
hydrolysed polyvinyl acetate with phthallic
anhydride.
oMainly used in coating of enteric tablets.

11. HPMC PHTHALATE
oDerived from HPMC by esterification with
phthalic anhydride.
oDissolve at a lower pH than CAP or Acrylate
polymers, hence can increase the bioavailability of
some drugs.

The basic or starting composition of a tablet coating is
obtained from the past experience or various sources of literature.
The composition of a tablet coating material includes :-
Coat or film formers
 Alloying substance
Solvent system
Plasticizer
Opaquant extenders
Colourants
Glossants
Anti – Oxidants
Flavours & Sweetners
Surfactants
Anti – Microbials
TABLET COATING COMPOSITION

Most of the tablet coating process uses one of
the following 3 major types of equipment
TABLET COATING EQUIPMENTS
3 MAJOR TYPES
PERFORATED
COATING PAN
CONVENTIONAL
COATING PAN
FLUIDIZED BED
COATING PAN

FLUIDIZED BED COATING PAN
Highly efficient coating systems
Mainly consists of a vertical chamber
Tablets are first filled into the vertical chamber – this
process is called Charging.
Fluidization of tablets are achieved by upward flow of
air.
Air stream first enters the column which causes the
tablets to rise in the centre.
Tablets then fall towards the chambers wall
Then the tablets move downwards to enter the air
stream again.
Coating solutions are applied through spray nozzles
that are kept at the top or bottom of the vertical
chamber.

CONVENTIONAL COATING PAN
The standard or conventional coating pan system consists of
a circular metal pan mounted on a stand, tilted to an angle of
about 45℃.
The pan is about 8-60 inches in diameter and is rotated on a
horizontal axis by a motor.
The coating pan has a provision of hot air through an inlet
port.
The heated air is directed into the tablet bed and leaves
through an exhaust duct.
Temperature of the hot air is maintained, so that the
chemical constituents are not degraded or decomposed.
Coating solutions are applied by ladling or spraying the
coating material on to the tablet bed.
Spraying produces more faster and even distribution of the
coating solution.

General Diagram of Standard Coating Pan

To increase the spraying efficiency, conventional
coating pans were modified into three :-
CONVENTIONAL COATING PAN
PELLEGRINI
SYSTEM
IMMERSION SWORD
SYSTEM
IMMERSION TUBE
SYSTEM

IMMERSION TUBE SYSTEM
In this system, a tube is
immersed in the tablet bed.
The tube delivers the heated
air, and a spray nozzle is built in
the tip of the tube .
During this operation, the
coating solution is applied
simultaneously with the heated air
from the immersed tube.
Heated air flows upwards and
leaves the system by the exhaust
duct.
This enhances the drying
efficiency.

IMMERSION SWORD SYSTEM
In this system, a perforated
sword is immersed in the tablet
bed.
The perforated sword delivers
the heated air.
During this operation, the
coating solutions are applied by
an atomised spray system directed
to the surface of the rotating pan.
Heated air flows upwards from
the sword through the tablet bed
and leaves the system by the
exhaust duct.
This enhances the drying
efficiency.

PELLEGRINI SYSTEM
In this system, baffled
plates and diffusers are
present.
Baffled plates are
installed to improve
blending and turning
over the tablet bed.
This also helps in
distributing the drying
air uniformly.

PERFORATED COATING PAN
In this system, all equipments of this type, consists of
perforated or partially perforated drum that is rotated
on its horizontal axis in an enclosed housing.
Drying air is applied to the tablet bed through
different ways in different types of perforated
coating pans.
In all the types of perforated coating pans, the
coating solutions are applied to the surface of the
rotating tablet bed through spraying nozzles that
are positioned inside the drum.
Perforated pan coaters are efficient drying systems
with high coating capacity, and can be completely
automated for both sugar coating and film coating
processes.

To increase the spraying efficiency, perforated
coating pans were modified into four :-
PERFORATED COATING PAN
DRIA COATER PAN
SYSTEM
GLATT COATER
SYSTEM
ACCELA –
COTA SYSTEM
HI - COATER PAN
SYSTEM

ACCELA – COTA SYSTEM
Consists of baffles, spray gun and dry air
inlet.
Baffles – freely mix tablets within drum when
rotating.
Spray gun – atomizes coating solution.
Drying air directed into the drum, is passed
through the tablet bed, and is exhausted through
perforations in the drum.
Process is fast and drying efficiency is also
good.

HI - COATER SYSTEM
Drying air directed into the drum, is passed
through the tablet bed, and is exhausted through
perforations below the coating drum.
This decreases the coating time.

DRIA - COATER SYSTEM
Drying air is introduced through hollow perforated
ribs located on the inside periphery of the drum.
As the pan rotates, the ribs dip into the tablet bed, and
drying air passes up through and fluidizes the tablet bed.
Exhaust is from the back of the pan.

GLATT COATER SYSTEM
Drying air can be directed from inside the drum
through the tablet bed and out an exhaust duct,
alternatively with an optional split chambered plenum.
Several airflow configurations are possible.

COATING
DEFECTS
BLISTERING CHIPPING
CRATERING
STICKING &
PICKING
BLOOMING
COLOUR
VARIATIONBRIDGING/
INFILLING
TWINNING
ORANGE
PEEL
CRACKING
BLUSHING
TABLET COATING DEFECTS

BLISTERING
An un-smooth coated surface shows a
number of uneven spots called blisters.
Causes – effect of temperature on the strength,
elasticity and adhesion of the coat.
Remedy – use mild drying condition.

CHIPPING
Defect where film become chipped and
dented, usually at the edges of the tablet.
Causes – excessive attrition during coating.
Remedy – increase hardness of film.

CRATERING
Defect of film coating where volcanic like
craters appears exposing the tablet surface.
Causes – penetration of coating solution into the
surface of the tablet.
Remedy – decrease in spray application rate
- use of optimum drying.

STICKING & PICKING
Defect where isolated areas of films are pulled
away from the surface when the tablet sticks
together and then part.

TWINNING
Two tablets stick together.
Causes – improper evaporation of coating
solution.
Remedy – reduce spray rate and increase
coating pan speed.

BLOOMING
Coating becomes dull immediately or after
prolonged storage.
Causes – using low molecular weight
plasticizer.
Remedy – increase molecular weight and
concentration of plasticizer.

BLUSHING
Defect where white specks are precipitated on the
film
Causes – excessive high coating temperature
Remedy – decrease drying air temperature.

COLOUR VARIATION
Either individual tablet colour variation or
whole batch colour variation.
Causes – improper mixing, uneven spray attern,
insufficient coating, mottling of dyes, plasticizer
etc.
Remedy – use of lake dyes eliminates mottlin,
reformulation with different plasticizer and other
addictives.

BRIDGING / INFILLING
Coating fills in the letter or logo on the tablet.
Causes – improper formulation, poor logo design,
improper application of coating solution, improper
atomization pressure, high viscosity of coating.
Remedy – addition of alcohol to polymer solution
increases dispersion.

ORANGE PEEL
A surface defect resulting in the film being rough
and non - glossy. Appearance is similar to that of a
peeled orange
Causes – inadequate spreading of coating solution
before drying, high solution viscosity
Remedy – use mild drying conditions, addition of
solvents to reduce viscosity

CRACKING
Small fine cracks observed on the upper and
lower central surface of tablets
Causes – use of high molecular weight polymers,
high internal stress
Remedy – use low molecular weight polymers or
polymeric blends.

CONTENTS
 Non – Official Tests of Quality Control of Tablets
 Official Tests of Quality Control of Tablets

INTRODUCTION
In Process Quality Control tests are
routinely run to monitor the compression and
manufacturing process.
Quality Control Tests are generally
divided into two :-
1. Non – Official Tests
2. Official Tests

NON – OFFICIAL TESTS
GENERALAPPEARANCE
TESTS
SIZE &
SHAPE
IDENTIFICATION
MARKINGS
ORGANOLEPTIC
PROPERTIES

GENERALAPPEARENCE
General appearance of a tablet is essential for
consumers acceptance, for control of batch to batch
uniformity, or tablet to tablet uniformity.
This involves the evaluation of :- size, shape, colour,
odour, taste, surface texture, physical flaws,
consistency, and legibility of identification markings.

1. SIZE & SHAPE
Should dimensionally described, monitored
and controlled.
Thickness of the tablet may be measured
using micrometer, or sliding caliper scale .
Physical dimensions control the weight of
the tablet.

MICROMETER
SLIDING
CALIPER
SCALE

II. IDENTIFICATION MARKINGS
Manufacturing companies use unique
markings on the tablet, in addition to the
colour used :- rapid identification of the
product.
Identification markings include :- symbols,
company name, product code, product name,
or product potency
Therefore markings on the tablet should be
evaluated for a quality product.

III. ORGANOLEPTIC PROPERTIES
Uniformity of the colour must be achieved within
the batch of tablets. Non –uniformity of the colour
shows a poor product.
Presence of odour in a batch of tablets could
indicate a stability problem, such as poor smelling
odour in aspirins, if acetic acid in the tablet
degrades. However, presence of odour in some
tablets could be a character of the tablets, such as
flavourful odour in vitamin tablets.
A tablet level of defects such as chips, cracks,
contamination from foreign substances (presence
of hair, oil droplets, or dirt), surface texture
(smooth or rough), appearance (dull or shiny)
should be evaluated – should be zero defect.

OFFICIAL TESTS
9 TYPES
HARDNESS
CONTENT
UNIFORMITY
FRIABILTY
API % TEST
DISINTEGRATION
TEST
% WEIGHT GAIN
IN COATED
TABLETS
THICKNESS OF
FILM IN COATED
TABLETS
DISSOLUTION
TEST
WEIGHT
VARATION

HARDNESS TEST
Tablets require a certain amount of strength or
hardness during transportation and handling.
Generally, greater compression force is applied,
harder the tablets,
Certain tablets such as lozenges or buccal tablets are
intended to dissolve slowly, so they are made
intentionally hard.
For tablets meant for immediate release, they are
intentionally made soft.
Tablets should be sufficiently hard to resist breaking
during normal handling and soft enough to
disintegrate properly after swallowing.

APPARATUS 1- MONSANTO HARDNESS
TESTER
This apparatus has a spring, screw knob, and a
graduated scale.
The reading on the graduated scale is adjusted to
zero.
The tablet to be tested is placed between the anvil
and spindle .
The screw knob moves forward until the tablet
breaks.
Note down the reading on the graduated scale,
which indicates the force required to break the
tablet. The force is measured in kilograms.

ANVIL
TABLET
SPINDLE
SCREW
KNOB
GRADUATED
SCALE

APPARATUS I1- PFIZER TESTER
The tablet to be tested is placed between the jaws
of the apparatus.
The reading on the pressure dial is adjusted to zero.
Then the press the plier like handle with hands.
Reading on the pressure dial is noted which
indicates the force required in kilogram or pound –
which is the force required to break the tablets.

PRESSURE
DIAL
TABLET
PLIER LIKE PRESS

FRIABILITY TEST
Done to check the ability of a tablet to break into
smaller pieces under pressure, mechanical shock, or
stress during handling and transportation.
Strength of the tablet plays an important role in
the dissolution and disintegration of the tablet.
After the friability test, tablets are inspected for
breakage and the percentage of tablet mass lost
through chipping.

APPARATUS – ROCHE FRIABILATOR
Consists of a drum or plastic chamber having diameter
283-291mm and a depth of 36-40mm.
Rotation speed of drum is 25rpm.
Carefully weigh 20 tablets and place them in a plastic
chamber and rotate it for 4 minutes or set 100 number of
rotations.
During each revolution, tablets fall from a distance of
about 6 inches. After 100 revolutions or 4 minutes,
remove the tablets from the chamber.
Dust the tablets and reweigh the tablets.
Percentage weight loss is calculated.
If there is a loss in weight, this indicates friability.
Loss of 0.5-1% of the weight is considered acceptable.

WEIGHT VARIATION TEST
20 tablets are randomly selected and weighed individually.
Average weight of the 20 tablets are also calculated.
Individual weight is compared with the average weight.
Not more than the individual weight of two tablets may
deviate from the average weight, by more than the
percentage deviation.
AVERAGE WEIGHT PERCENTAGE
80mg or less 10
8-250mg 7.5
250mg or more 5

CONTENT UNIFORMITY TEST
According to United States Pharmacopoeia, 10
tablets are assayed individually.
Out of this, 9 tablets should not contain less than
85% or more than 115% of the labelled drug content.
10th tablet should not contain less than 75% or more
than 125% of the labelled drug content.

ACTIVE PHARMACEUTICAL
PERCENTAGE TEST
Percentage of medicament or active pharmaceutical
ingredient, are calculated by taking sample of tablets
and then assay is carried out.
Result of the tablets should be within the prescribed
percentage limit in pharmacopoeia.

DISINTEGRATION TEST
Generally, when a drug is taken, it should be readily
available to the body.
First important step of a tablet to be readily available
:- breakdown of the tablet into smaller particles or
granules – process is called Disintegration.
Time taken for a tablet to disintegrate is
measured in a device described in the USP.
Disintegration is mainly used as a guide for the
formulator in preparing an optimum tablet
formulation.

APPARATUS – DISINTEGRATION
APPARATUS
The USP device for disintegration comprises – 6
glass tubes that are 3 inches long, open at the top,
and closed at the bottom with a 10 mesh screen in the
basket rack assembly.
One tablet is placed in each tube and a perforated
plastic disc is placed over the tablet.
The basket rack is positioned in a 1litre beaker of
water or simulated gastric fluid or intestinal fluid, at
37℃.
The assembly moves up and down at a specified rate
using the help of a standard motor driven device.
Time taken to disintegrate the tablets, and all
particles must pass through the 10 mesh screen in
the standard time.

Uncoated tablets :- water is used a disintegration
medium, and all 6 tablets should disintegrate within 15
minutes.
Sugar Coated tablets :- all tablets should disintegrate
within 1 hour. If a tablet does not pass the test, the
disintegration medium is changed from water to 0.1M
HCl, and the test is repeated. Failure in this, will lead to
rejection of the whole batch.
Film coated tablets :- tablets should disintegrate in 30
minutes.
Enteric coated tablets :- test is carried out for 2 hours
first in 0.1 M HCl, and the tablets should not disintegrate.
Then the tablets are tested with a simulated intestinal
fluid for the next hour.

DISSOLUTION TEST
Dissolution test is carried out to :-
Show that the drug is released up to 100%.
Show that the drug release is uniform batch to
batch.
There are different types of dissolution apparatus
according to the United States Pharmacopoeia.

In general, dissolution apparatus consists of a cylindrical
flask with a hemispherical bottom, made of glass or
transparent plastic having 1000ml volume capacity.
Flask is partially immersed in a temperature bath
maintained at 37℃.
Flask is fitted with a cover having 4 holes – one hole for the
shaft with a basket or paddle, second for thermometer, and
other holes for sampling.
Other end of the shaft is attached to variable speed driven
motor that rotates at 25-150 rpm.
Dissolution test is first conducted with 6 tablets, if a failure
occurs the test is repeated with 6 tablets. On failure again,
the test is repeated with 12 tablets.

APPARATUS I – ROTATING BASKET TYPE
A cylindrical basket is placed at the end of the
shaft, constructing with a non reactive mesh.
Tablet is placed in the basket, and the pores in the
mesh allow the dissolving drug to move from the
basket to the holding flask.
Start motor and seed is adjusted to 100 rom.
At a specified time interval, sample is withdrawn
and the same volume of dissolution medium is
replaced.
Samples are tested by UV spectroscopy, or
chromatography.

APPARATUS II – PADDLE TYPE
Rotating shaft is fixed to a blade attached
vertically at the end.
The blade is meant to act as a stirrer to ix the
drug being tested with the liquid.
Drug is placed in the flask.
Start motor and seed is adjusted to 100 rom.
At a specified time interval, sample is withdrawn
and the same volume of dissolution medium is
replaced.
Samples are tested by UV spectroscopy, or
chromatography.

PERCENTAGE OF WEIGHT GAIN IN
COATED TABLETS
Difference in weight of the final product and the
initial uncoated tablet is calculated and the percentage
is noted and checked according to the standard values
in the pharmacopoeia.

THICKNESS OF FILM IN COATED
TABLETS
Difference in the thickness of the coated tablet and
uncoated tablet is measured using a micrometer or
sliding caliper scale.
Note the value is noted and checked according to the
standard values in the pharmacopoeia.

TABLETS

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