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Mr. Dipak B. Bhingardeve
Assistant Professor
Department of Pharmaceutics
Dr.Shivajirao kadam college of Pharmacy
,kasabe digraj ,Sangli.
Introduction
 Tablets are solid dosage form containing medicament or
medicaments, usually circular in shape and may be flat or
biconvex.
 Tablets are prepared by the compression method and are
hence called the ‘Compressed Tablets’.
 Advantages :
 Easy to be administered, dispensed, more stable.
 Maintain the accuracy of dosage.
 Bitter & nauseous substances can be given easily in tablet
form after giving a suitable coating to the tablets.
 They are lightest & most compact, economical dosage
form.
Disadvantages:
 Some drug resist compression into tablet form due to their
amorphous nature or low density character.
 Bitter tasting drugs, drugs with objectionable odour or
drugs that sensitive to oxygen or atmospheric moisture may
require encapsulation.
 The tablets cannot be used in case of emergency cases,
because the rate at which active ingredient reaches the site
to be treated slow.
 Bioavailability of some drugs may be low due to poor
absorption from the gastric tract.
Types of tablets
A)Tablets ingested orally:
 Oral tablets are designed to be swallowed as they are except
the chewable tablets.
 Compressed tablet(C.T.):
 Uncoated and made by compression of granules.
 Provide rapid disintegration and drug release.
 Multiple compressed tablets(M.C.T.):
 These tablets are prepared to separate physically or chemically
incompatible ingredient or to produce prolonged action.
 To avoid incompatibility, the ingredients of the formulation
except incompatible material are compressed into a core
tablet and
 Then incompatible substance along with necessary excipients
are compressed over previously compressed core tablet.
Multilayered tablets :
 Consist of two or more layers of materials compressed
successively in the same tablets.
 Colour of each layer may be same or different.
 Tablets having layers of different colours are known as
“Multicoloured tablets.”
 Sustained action tablets :
 Used to get sustained action of medicament.
 These tablets when taken orally, release the medicament in
sufficient qty as & when required to maintain the maximum
effective concentration of the drug in blood throughout the
period of treatment.
 Enteric coated tablets:
 These are compressed tablets meant for administration by
swallowing and are designed to bypass the stomach & get
disintegrated in the intestines only.
Sugar coated tablets:
 Compressed tablets having sugar coating are called “sugar
coated tablets.”
 Sugar coating is done to mask the bitter and unpleasant
odour and the taste of the medicament.
 Film coated tablet:
 Having film coating of some polymer substance ,such as
HPC,HPMC,EC.
 Film coating protects the medicament from atmospheric
effects.
 Tablets generally tasteless, having less elegance than that
of sugar coated tablets.
Chewable tablet:
 Tablets are chewed in the mouth and broken into smaller pieces.
 In this way, disintegration time is reduced and rate of absorption
of the medicament is increased.
 B) Tablets used in oral cavity :
 Buccal tablets :
 Tablets are placed in buccal pouch or between gums and lips or
cheek where they dissolve or disintegrate slowly & are absorbed
directly without passing into the alimentary canal. e.g Tablet of
ethisterone.
 Sublingual tablets :
 These tablets are placed under the tongue where they dissolve or
disintegrate quickly and are absorbed directly without passing
GIT. E.g Tablet of Glyceryl trinitrite
Lozenges tablets and troches:
 Tablets are designed to exert a local effect in the mouth or
throat.
 Used to treat sore throat or to control coughing in common
cold.
 They may contain local anaesthetics, antibacterial agents,
astringents and antitussives.
 Prepared by compression at a high pressure or by moulding
process. Generally contain sweetening agent & flavouring
agent.
 Dental cones :
 Minor compressed tablets meant for placing them in the
empty sockets after tooth extraction.
 They prevent multiplication of bacteria in the socket.
 Tablet contains lactose, sodium bicarbonate & sodium
chloride.
C) Tablets administered by other routes
 Implantation tablets:
 Tablets are placed under the skin or inserted subcutaneously by
means of minor surgical operation and are slowly absorbed.
 These may be made by heavy compression but are normally
made by fusion.
 Mainly used for administration of hormones such as
testosterone and deoxycorticosterone etc.
 Vaginal tablets :
 Tablets are meant to dissolve slowly in the vaginal cavity.
 This tablet form is used to release steroids, antibacterial agents,
antiseptics to treat vaginal infections.
 Contains excipients such as, lactose or sodium bicarbonate.
D)Tablets used to prepare solution
 Effervescent tablets :
 These tablets when added in water produce effervescence. So
they dissolves rapidly in water due to chemical reaction .
 These tablets are to be protected from atmospheric moisture
during storage.
 So ,tablets should stored in well closed air tight container.
 Dispensing tablets :
 Tablets to be added to a given volume of water to produce a
solution of given concentration.
 Contains excipients which gets dissolves quickly to form a clear
solution.
Hypodermic tablets
 These are compressed tablets which are composed of one
or more drugs with readily water soluble ingredients.
 Tablets are dissolved in sterile water or water for injection
and administered by parenteral route.
Manufacturing of compressed tablets
 Steps involves during manufacturing of compressed
tablets:
 I. Preparation of granule for compression:
 a) Weighing of ingredients
 b) mixing of powdered ingredients & excipients
 c) converting the mixed ingredients into granule.
 II. Compression of Granules into tablets.
 III. Coating of tablets.
 IV. Quality control of tablets.
I.Preparation of granules for compression.
 A) Weighing of ingredients:
 Ingredients should weighed accurately using a balance of good
quality.
 B) Mixing of powdered ingredients and excipients .
 The main objectives of this is to prepare a homogenous mass,
so that uniform tablets can be manufactured.
 C)Converting the mixed ingredients into granules:
 The crystalline medicament can be compressed to get good
quality compressed tablets.
 In case the medicament along with excipients are in powder
form it cannot be compressed as such into tablet
Because :
The granules can be prepared by following methods:
 1. Moist granulation method:
 2. Dry granulation
 3. Granule by preliminary compression
 1. Moist granulation method:
 This is oldest and still most widely used method of tablet
preparation.
 The powdered and mixed tablet constituents are converted
into moist coherent mass by wet screening .
 This method involves following steps:
Steps:
 1. Milling of drugs and excipients.
 2.Mixing of milled drugs and excipients.
 3.Preparation of binder solution.
 4.Mixing of binder solution with powder mixture to form wet
mass( Granulation step).
 5.This wet mass is then passed through Sieve no.8 or 10.
 6.Drying the moist granules.
 7.The dried granules are passed through Sieve number 20 to collect
the granule of uniform size.
 8.Then mixing of these dried granules with lubricating agent and
disintegrating agent.
 9.Granule are then ready to be compressed.
Steps for wet granulation process
 Weighing Mixing Granulation (wet mass)
 Wet sieving
 Drying
Compression Mixing Granule dry sieving
 (lubricant & disintegrant) (ready for
 compression)
2. Dry granulation
 There are certain medicaments which are available in
crystalline form or in the form of granule having its own
binding property.
 Such medicament are passed through sieve No.20 or any
other specified sieve .
 And then mixed with any additional excipient.
 This method is used for making tablet of aspirin, sodium
bromide, potassium chlorate etc.
3. Granules by preliminary compression:
 This method is also known as ‘slugging method’.
 Method is used in those cases where the medicament is
unstable in presence of moisture.
 In this process the dry powder is compressed into large tablets
or “slugs.”
 These slugs are broken into small pieces which are passed
through a specified sieves to collect the granules of suitable
size.
 A lubricating agent and disintegrating agents are mixed with
these granules before compression into tablet machine.
Excipients used in formulation of tablets:
 An excipient is an inert substance which is added along
with medicament to prepare the granules from the solid
medicaments.
 1. Diluents
 2. Granulating agents
 3. Binding agent
 4.Disintegrating agent
 5.Lubricants
 6.Adsorbents
 7.Colouring agents, flavouring agents &
sweetening agent.
1.Diluent:
 The diluents is needed in the formulation of a tablet, when the
quantity of medicament in each tablet is very small and it is
not possible to make a good tablet.
 E.g.lactose,sucrose,sodium chloride,dextrose,and starch,
mannitol,sorbitol,dibasic calcium phosphate dihydrate etc.
 2.Granulating agents:
 These are used to convert the fine powder into granules.
 These agent provided proper moisture to convert fine powder
into damp mass, after passing through a sieve of suitable
number forms granules.
 E.g water ,alcohol, mucilage of starch, mucilage of acacia,
mucilage of tragacanth,gelatin solution, isopropyl alcohol,
acetone etc.
3.Binding agents
 These are used in granulation to provide proper strength to
granules, in order to keep the tablet intact after compression.
 E.g Gum acacia powder ,gum tragacanth, gelatin, sucrose,
methyl cellulose etc.
 4. Disintegrating agents:
 The substance which are added in the tablet formulation to
ensure disintegrating of the tablets into smaller particles when
swallowed are called “Disintegrating agents.”
 These are added into formulation of or oral tablets or
sublingual tablets.
 When the medicament is insoluble in water a disintegrating
agent is needed.
Disintegrating agents act in three ways:
 I) By swelling :
 Disintegrating agent gets swelled when it comes in contact
with water or moisture e.g. Potato starch ,maize starch ,wheat
starch , Methyl cellulose and Bentonite.
 II)By producing effervescence:
 They produce effervescence when they come in contact with
moisture , e.g. sodium bicarbonate , citric acid and tartaric
acid.
 III)They melt at body temperature e.g Cocabutter.
 The disintegrating agent is generally divided into two
parts.
 One part is mixed along with other excipients before the
formation of granules.
 Other part is mixed with dry granules before compression.
5. Lubricants:
 These are added to improve the appearance of tablets, flow
properties of granules & to prevent the sticking of the
material to the dies and punches.
 Lubricants are divided into three group:
 i) Lubricants: Substance that reduce intergranular friction
during compression and friction between tablet and die wall
during the ejection of tablet.
 E.g Talc, Magnesium stearate and calcium stearate etc.
 ii) Glidants: They improve the flow properties of the
granules from hopper to die of the tablet machine.
 E.g. Talc, sodium chloride ,magnesium stearate ,boric acid,
starch and calcium stearate etc.
 Iii) Anti-adhesive agents : These prevent sticking of tablet
surface to dies & punches during compression.
 E.g liquid paraffin, mg stearate etc.
6.Absorbing agents:
 These substances are used to absorb volatile oil, liquid extract
and tincture etc. Which are included in the formulation of
tablets.
 E.g- mg carbonate ,kaolin and starch.
 7. Colours, flavours and sweetening agents:
 The colours are used to improve the elegance of the tablet.
 Flavours are volatile oils and hence they are added into the
granules just before compression of tablets.
 Flavouring agents is dissolved in organic solvent and the
solution is sprayed on the granules.
 Sweetening agents are used to improve the taste of tablets.
 These are used in lozenges & chewable tablets.
 Sucrose, lactose and mannitol are some of the commonly used.
II) Compression of Granules into Tablets:
 The dried granules are compressed into tablets in a machine
known as a tablet making machine .
 The various type of machine :
 1.Single punch tablet machine which may be hand
operated or electrically operated.
 2.Multipunch tablet machine
 3.Rotary tablet machine
 4.Dry cota tablet machine
 In all these machine compression is achieved by filling the
required qty of granules into dies and then compressing them in
between the lower punch & upper punch .
 Single punch is used for small scale mfg, whereas other
machines are used for large scale mfg.
 Rotary machine having about 70 sets of dies produce about 1200
tablets in one minute.
1.Single punch tablet machine:
 Major parts :
 A) Hopper shoe: To supply the granules to the die & remove the
tablet after its compression.
 B)Lower punch:
 C)Upper punch:
 D) Capacity regulator: To adjust the position of the lower
punch to accommodate the required qty of granule by die.
 E)Ejection regulator: to adjust the position of the lower punch
,so that its highest position is at par with surface of the die.
 F) Die: It allows the lower punch and the upper punch to come
close together to compress the granules.
 G)Driving wheel: it helps in the movement of the lower punch,
upper punch & hopper shoe & also check their movement.
Working :
 The cycle of movement of Tablet machine is as:
 1. The upper punch rises to allow the hopper shoe to move over
the disc.
 2. The lower punch drops and granules feed from shoe into the
die.
 3.The shoe moves aside & the upper punch drops, thus
compressing the granules into a tablet.
 4. The upper punch rises upward and the lower punch rises upto
the surface of the dies to eject the tablet.
 5. The hopper shoe again moves forward over the dies, pushing
aside the newly formed tablet.
 The lower punch drops and the cycle is restarted.
2.Multi –punch tablet machine:
 There are 2 to 12 dies on a big platform.
 The number of punches depends upon the number of
dies fixed to the platform.
The working is similar to single punch machine but in this
machine in one stroke as many tablets are compressed as
the number of dies.
3. Rotary tablet machine :
 A rotary tablet machine is used for large scale economic
production.
 In this machine about 1200 tablets are prepared in one minute.
 There are 70 sets of dies and punches .
 This machine has a circular rotating head, carrying a number
of punch and dies assembles.
 Head revolves continuously while the tablet granulation runs
from hopper through feed frame & into dies .
 There is uniform filling of the die due to this arrangement &
therefore the tablets formed in rotary tablet machines have an
accurate uniform weight.
 Compression is done when upper and lower punches pass
between pair of rollers.
 The tablet comes out when the lower punch lifts up.
4. Dry cota tablet machine :
 The machine is used for manufacturing of multi-compressed,
multi-coloured and press-coated tablets.
 In this machine two rotary machines work simultaneously
by a single driven shaft.
 The core tablet is prepared in one machine which is
transferred to the second machine for compress coating.
Manufacturing defects in tablets.
 1. Capping :
 In this case there is partial or complete removal of top or
bottom portion of the tablet.
 Reason for this effect:
 Excessive fines in granules which entrap air in a tablet.
 Defective punches and dies.
 High speed of tablet machine .
 The granules are too dry.
 There is an usually high degree of compression.
Defects can be removed by
 Setting the dies and punches properly.
 To reduce the percentage of fines.
 Maintain desired moisture content level in granule.
 Regulate the speed of tablet machine.
 2. Picking and sticking :
 Material is removed or picked up by the upper punch
from the upper surface of the tablet.
 In case of sticking ,the material sticks to the wall of the
die.
Reasons :
 Use of worn out dies and punches.
 Use of small qty of lubricants.
 Presence of moisture in the granule.
 Excess of powder in the granules.
 Defects can be removed by:
 A new set of die and punches.
 A proper quantity of lubricants in the granules.
 Dry granules.
3. Mottling :
 Mottling means an unequal distribution of colour on the
surface of a coloured tablets.
 Reasons :
 Migration of dye in the granules during the process of drying .
 Use of different coloration of medicament and excipients.
 Defects can be avoided by;
 Drying the granule at low temperature.
 Using the dye which can mask the colour of all the ingredients
of tablet formation.
4. Weight variation:
 During the compression of granules in a tablet machine , the
tablets do not have a uniform weight.
 Reasons;
 Granules are not uniform in size.
 Presence of excess amount of powder in granules.
 No proper mixing of lubricants.
 No uniform flow of granules from the hopper to the die.
 5. Hardness :
 Hardness depends on the weight of material &the space
between the upper & lower punches during the stages of
compression.
 If volume of material varies or the distance between punches
varies ,the hardness will also vary.
6. Double impression :
 This defects occurs when the lower punch has a
monogram or some other engraving on it.
 During compression, the tablets receives an imprint of the
punch.
 Due to some defects in the machine, lower punch moves
slightly upward before ejection of a tablet and gives a
second, imprint on the tablet.
 This can be removed by controlling the undesirable
movement of the lower punch.
III.Coating of tablets:
 Purposes :
 1.To mask the unpleasant taste and odour.
 2.To improve the appearance of tablets.
 3.To prevent the medicament from atmospheric effects.
 4.To control the site of action of drugs (Enteric coating )
 5.To produce the sustained released product.
 Tablet coating generally done by
 1. Pan coating
 2.Press coating
1. Pan coating :
 Coating is done in pan which is made up of copper/
stainless steel.
 Pan is rotated with help of electric motor.
 The tablet to be coated are placed in the pan.
 Hot air is blown in.
 Speed of pan is adjusted in such a way that tablet remain
separated from each other in the pan.
Cont..
 After coating ,polishing is done in a polishing pan.
 Pan coating is used for sugar coating ,film coating and enteric
coating.
 2. Press Coating:
 In this technique the granules of coating material are prepared
 & layer of coating material is placed on preformed tablet
(below & above the tablet to be coated) in Drycota Rotary
Tablet Machine.
 The whole operation is carried out automatically in a number
of steps.
Sugar coating :
 Sugar coating is done by pan coating method.
 Various stages in the sugar coating process are:
 1. Sieving 2.Sealing
 3.Subcoating 4. Syrup coating
 5.Finishing 6.Polishing
 1. Sieving :
 The tablets to be coated are shaken in a suitable sieve to
remove the fine powder or broken pieces of tablet.
2.Sealing :
 Sealing is done to ensure that a thin layer of water proof material,
such as, shellac or cellulose acid phthalate is deposited on the
surface of the tablet.
 The shellac or cellulose acid phthalate is dissolved in alcohol or
acetone.
 The pan is rotated with the help of an electric motor.
 There is arrangement of hot air to be supplied inside the coating
pan.
 The speed of pan is adjusted in such a way that the tablets
remain separated from each in pan.
 Nowadays ,it is done by fluidised bed coating or spray
techniques.
3.Subcoating :
 In subcoating ,several coats of sugar and other material, such
as, gelatin, acacia etc. are given to round off tablet and to
help in building up the tablet size.
 After each addition of syrup dusting powder is sprinkled.
 The dusting powder is a mixture of starch, talc and powdered
acacia.
 Dusting powder does not allow the tablet to stick together.
 The hot air is blown inside the coating pan which is rotated
at a suitable speed.
Cont...
 This ensure proper drying of the syrup coat.
 The alternative addition of syrup and dusting powder is
repeated until a coating of the required thickness is produced.
 At end of process, warm syrup without dusting powder is used
to obtain a smooth surface.
4.Syrup coating :
 This is give sugar coats, opacity and colour to the tablet.
 Several coats of the syrup are applied.
 Colouring materials and opacifying agents are also added
to the syrup.
 The process of coating is repeated until uniform coloured
tablets are obtained.
5.Finishing:
 3 to 4 coats of syrup are applied in rapid succession without
dusting powder and cold air is circulated to dry each coat.
 This forms a hard smooth coat.
 6.Polishing :
 Beeswax is dissolved in volatile organic solvent and a few coat
of it are given.
 The finished tablets are transferred to a polishing pan which is
rotated at a suitable speed so that the wax coated tablets are
rubbed on the canvas cloth.
 The polishing pan is rotated at a suitable speed so that the wax
coated tablets are rubbed on the canvas cloth.
 This gives a proper shining to the tablets.
Film coating :
 In this case the tablets are coated by a single or mixture of film
forming polymers ,such as, HPMC, Carbowax, hydroxyethyl
methyl cellulose, polyethylene glycol 400 etc.
 The polymer is dissolved in some volatile solvent and is sprayed
over the tablets in rotating pan.
 The process is continued till uniform good film is formed over
the tablet.
 Film coating is also used to make the tablet water proof before
the sugar coating .
 Film coating can be enteric or non-enteric.
Advantages:
 It is less time consuming technique.
 Not much labour required .
 It has o adverse affect on disintegration of tablet.
 The product cost is low because the material used for
coating is quite cheap.
 It protects the drug from atmospheric changes, such as
light, air, and moisture.
 Coating is resistant to cracking and chipping.
 Tablet become elegant.
Enteric coating :
 Enteric coating is given to the tablet in order to ensure
that these tablets will not disintegrate in the stomach but
pass through it as they are.
 Such tablets get disintegrated in the intestines.
 Coating is done due to reasons:
 Medicament produce severe irritation in the stomach.
 The action of medicament is required in the intestine.
 E.g anthelmintics and amoebicides are required to be
absorbed from stomach.
 Drug absorption is better in the intestines.
 Delayed action is needed.
Ideal properties:
 Resistance to gastric fluids.
 Non-toxic in the required quantity.
 Economical.
 Formation of a continuous film.
 Compatible with drug on which coating is done.
 On large scale, the enteric coating of tablets is done in a
rotating pan.
 Solution of enteric coating material such as, salol, cellulose
acetate phthalate, shellac and its derivatives are prepared in a
volatile organic solvent.
 The solution is sprayed over the tablets which are rotated in the
coating pan.
Cont...
 The hot air is blown into the pan which helps in the evaporation
of organic solvent.
 Hence , a fine film of enteric coated material is made over the
tablet.
 The process is repeated a number of times till required number
of coatings are done.
Microencapsulation
 Microencapsulation is a process or technique by which thin
coating can be applied to small particles of solids ,droplets of
liquid or dispersion, thus forming microcapsules.
 The microcapsules may consist of a single particle or clusters of
particles.
 It differs from other coating methods because microencapsulation
process is used to coat the particles having a particle size range
from several tenth of a micro to 5000 µ.
Microencapsulation techniques :
 1.Pan coating
 2.Fluidised Bed coating
 3.Coacervation
 4. Electrostatic Deposition
 5.Vacuum Deposition
 6.Polymerisation
 7.Multiorific centrifugal process.
Pan coating :
 This technique is suitable in those cases where the particle
size is larger than 6000 µ.
 The coating material is dissolved in a suitable volatile organic
solvent and sprayed in the pan.
 Hot air is circulated in the pan.
 Fluidised bed coating :
 Particle of solid core material are suspended in the turbulent
current of air in a chamber.
 The solution of coating material is prepared in the volatile
solvent & atomised in the chamber thr nozzles.
 Temperature is regulated in such a way that volatile solvent
gets vaporised.
Cont...
 After coating ,the solid particles become quite heavy and fall
on the screen near the outlet from where these can be
removed .
 Coacervation:
 Coacervation means the separation of liquid or phase
when solution of two hydrophilic colloids are mixed under
suitable condition.
 In this method , three immiscible phases of core material,
solvent and coating material are formed followed by
deposition of coating material on core.
 The coating material is dissolved in a suitable solvent and the
core material is uniformly dispersed in the soln of coating
material.
Electrostatic deposition
 Method is useful both for solid particle and liquid droplets.
 In this , core and coating material are electrically charged by
means of high voltage such as 10,000 volts etc.
 Core is charged and placed in coating chamber.
 The coating material is also charged before it is sprayed as a
mist.
 Because charges are of opposite kind, the coating material gets
deposited on the core due to electrostatic attraction.
 Vacuum deposition :
 Coating material is vaporised in a chamber under vacuum of
the order of 10-2 to 10-5 mm, in which the core material is
present.
 The coating material gets deposited on the core particles.
Polymerisation :
 Core material is dispersed in a liquid or a gas in which
monomeric units of coating material are present.
 These monomers gets polymerised at the interface between the
core particles and the liquid gas phase which form coats over
the core.
 Multi –orifice centrifugal process:
 This is mechanical process for producing microcapsules.
 The method is capable of microencapsulating liquid and
solids.
 The particles of the core material are forced through an
envelope of coating material in solution by using centrifugal
force.
 This results in a mechanical microencapsulation of the core
particles.
Applications
 It is used for masking the taste of bitter drugs.
 It is used for preparing prolonged action of dosage form.
 Used to separate an incompatible material.
 Used to protect chemicals against moisture and oxidation.
IV) Evaluation of tablets
 1. Shape of tablets
 2. Appearance
 3. Content of active ingredient in tablets.
 4. Uniformity of weight
 5. Disintegration test for tablets
 6. Dissolution test for tablets
 7. Mechanical strength
 8. Friability test
1.Shape of tablet
 Shape of tablet as per pharmacopoeia is circular with flat or
convex faces.
 2. Appearance :
 Coated tablet have a smooth and often coloured surface.
 3.Content of active ingredient in tablet:
 The amount of active ingredient in tablet is determined by
doing the assay as stated in the monograph.
 Generally 20 tablets in the monographs are used in the assay.
 The result lies within the range for the content of active
ingredient stated in the monograph.
s
Cont..
 In such cases ,the limits specified in the monograph indicated in
table.
 The requirement of this table apply when the stated limit are
between 90 to 110 percent .
 4. Uniformity of weight :
 Every individual tablet in batch should be uniform in weight, but
a small variation in the weight of the individual tablet is liable to
occur.
 The following percentage deviation in weight variation is
allowed.
Cont...
 Weigh 20 tablets selected at random & determine their average
weight.
 NMT 2 of individual weight may deviate from average weight .
 And none should deviate by more than twice that percentage.
Sr.
no
Average weight of tablet deviation Percentage
1. 80 mg or less 10
2. More than 80 mg & less than 250 mg 7.5
3. 250 mg or more 5
5. Uniformity of content:
 Tablet must comply with requirement for uniformity of
content specified in the individual monograph.
 Percentage of medicament is calculated by doing assay for
particular drug.
 The variation in percentage of medicament per tablet is due
to the following reasons:
 1.Weighing of material before granulation
 2.Variation in the weight of an individual tablet.
 3.Error of random sampling
 4. Analysis error
 5.Purity of medicament.
Cont..
 As per the pharmacopoeia, 20 tablets are taken ,powdered and
assayed .
 The average weight of medicament present in each tablet is
calculated which is then compared with desired weight.
 The pharmacopoeia has prescribed the limit in percentage of
medicament per tablet in the monograph.
6. Disintegration test for tablet:
 Disintegration means to break the tablet into smaller particles
after swallowing.
 The time required to disintegrate the tablet is called
“disintegration Time”.
 The rate of disintegration is depends upon type of tablet.
 The test of disintegration is required in tablet which are
swallowed.
 In general pharmacopoeia prescribed a limited of 15 minutes.
Official disintegration test
 The apparatus consist of :
 A rigid basket-rack assembly supporting six cylindrical glass
tube.
 These tubes are held vertically by two superimposed transparent
plastic plates with six holes having same diameter.
 The upper and lower plates are held in position by vertical metal
rod which is attached to mechanical device.
 The assembly should be raised & lowered between 28 to 32 times
per minute in liquid at 37 ºC
Cont..
 The tablets are kept immersed in the liquid within the tube by
means of cylindrical guides discs.
 The assembly is suspended in the liquid medium in a 1000 ml
beaker .
 The beaker may be filled in such a way that the wire mesh at the
highest point is at least 25 mm below the surface of liquid and its
lowest point is at least 25 mm above the bottom of the beaker.
I) Method used for uncoated tablet:
 Place one tablet in each of 6 tubes of basket, add disc to each
tube & operate apparatus ,using water maintained at 37º ±2º .
 At the end of 15 minute, lift the basket from liquid & observe
the tablet.
 Tablet pass the test if all size tablets have disintegrated.
 In case one or two tablet fail to disintegrate ,repeat the test on
12 additional tablets.
 The tablets pass test if NLT 16 of total of 18 tablet tested have
disintegrate.
II) Method used for coated tablet:
 Place one tablet in each of the 6 tube of the basket,& if the tablet
has soluble external coating ,immerse basket in water at room
temperature for 5 min.
 Then add disc to each tube & suspend in water maintained at 37 º ±2º
C & operate the apparatus for 60 min.
 The tablet pass the test if all the six have disintegrated.
 In case any of tablets has not disintegrated, repeat the test on further
6 tablet replacing water with 0.1 N HCL.
 Tablet then pass the test if all six tablet have disintegrated in acid
medium.
 If one or two fail ,repeat the test on 12 additional tablets.
 Tab. Passes the test if NLT 16 of the 18 tablet tested get disintegrated.
III) Method used for enteric coated tablets:
 Place one tablet in a each of the six tubes of the basket and immersed
basket in water for 5 min at room temp.
 Operate apparatus without using disc for two hours. The basket is
immersed in 0.1N HCL at 37º± 2º.
 If no any tablet shows disintegration or cracks ,then add disc to each
tube & operate the apparatus using phosphate buffer having pH 6.8 as
immersion liquid at 37º± 2º.
 After 60 min, remove assembly and observe the tablets.
 The tablet pass test if all six tablets have disintegrated.
 If one or two fail , repeat the test on additional 12 tablets.
 The tablets pass the test if NLT 16 of the 18 tablets tested get
disintegrated.
7.Dissolution test for tablet
 The test is done for measuring the amount of time required for
given percentage of the drug substance in a tablet to go into
solution under specified condition in vitro.
 Apparatus : consist of following parts:
 1. A cylindrical covered vessel made of glass or other transparent
material having 1000 ml capacity & vessel is fitted with lid
having 4 holes ,one for having shaft of stirrer, second for placing
thermometer and remaining two for removing sample.
 2. An electric motor which is capable of rotating the basket in
the vessel at varied speed between 25 and 150 RPM.
Cont...
 3. A cylindrical stainless steel basket made of woven wire cloth
having an aperture size of 425 µm. The top of basket is attached
to the disc on the driving shafter.
 4.The vessel is equipped with suitable device for the withdrawal
of samples of dissolution medium.
 5. The vessel should be securely clamped in water bath
maintained at 37º± 2º having an arrangement for smooth motion
of water during the test.
Method:
 Place 1000 ml of water which should be free from dissolved air &
previously warmed to 36.5º to 37.5º into vessel.
 Place specified number of tablets in dry basket and set the
apparatus.
 Start the motor and adjust rotation speed to 100 rpm.
 Withdraw the stated volume of solution from vessel after 45min.
 Filter and determine the amount of active ingredient present in it.
 Repeat the complete operation 4 times.
Cont...
 The tablet pass the test if for each of five tablets , the amount
of active ingredient in solution is NLT 70 percent of the stated
amount.
 No –retesting is allowed.
 8. Mechanical strength :
 Pharmacopoeia has not fixed any standard for the mechanical
strength or hardness of tablets.
 The devices are commonly used to find out mechanical
strength of tablet:
 1. Monsanto hardness tester
 2.Pfizer tablet hardness tester.
1.Monsanto hardness tester
 The Monsanto chemical Co.ltd had designed spring pressure
device to test the hardness of a tablet.
 It has a graduated scale which gives the reading in kg/sq.cm.
 The tablet to be tested is placed between the spindle and the
anvil.
 The desired pressure needed to hold the tablet in position is
applied by moving the screw knob in clockwise direction.
 The scale is moved so that the indicator is fixed at zero.
 The pressure is then applied till the tablet breaks.
 The reading is noted, which indicates the pressure which is
needed to breaks the tablet.
2.Pfizer tablet hardness tester
 It is bases on the principle of an ordinary plier.
 Pfizer tablet hardness tester is plier fitted with a pressure dial.
 The tablet is placed between the jaw of the plier and pressure is
applied by pressing the handles with hand unit until tablet
breaks.
 The reading of the dial indicates the pressure needed to breaks
the tablet.
9. Friability test:
 Friability test is performed to evaluate the ability of teh
tablet to withstand wear and tear in packing ,handling and
transporting.
 The apparatus used to perform this test is known as
‘Friabilator’.
 Apparatus consist of :
 Plastic chamber, which is divided into two parts and it
revolves at a speed of 25 rpm.
 20 tablets are weighed and placed in the plastic chamber.
 The chamber is rotated for 4 minutes or 100 revolutions.
 During each revolution the tablet falls from distance of 6
inch.
Cont..
 Loss in weight indicates the friability .
 The tablets are considered to be good quality if the
loss in weight is less than 0.8 %.
Processing of tablet
Processing of tablet

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Processing of tablet

  • 1. Mr. Dipak B. Bhingardeve Assistant Professor Department of Pharmaceutics Dr.Shivajirao kadam college of Pharmacy ,kasabe digraj ,Sangli.
  • 2. Introduction  Tablets are solid dosage form containing medicament or medicaments, usually circular in shape and may be flat or biconvex.  Tablets are prepared by the compression method and are hence called the ‘Compressed Tablets’.  Advantages :  Easy to be administered, dispensed, more stable.  Maintain the accuracy of dosage.  Bitter & nauseous substances can be given easily in tablet form after giving a suitable coating to the tablets.  They are lightest & most compact, economical dosage form.
  • 3. Disadvantages:  Some drug resist compression into tablet form due to their amorphous nature or low density character.  Bitter tasting drugs, drugs with objectionable odour or drugs that sensitive to oxygen or atmospheric moisture may require encapsulation.  The tablets cannot be used in case of emergency cases, because the rate at which active ingredient reaches the site to be treated slow.  Bioavailability of some drugs may be low due to poor absorption from the gastric tract.
  • 5. A)Tablets ingested orally:  Oral tablets are designed to be swallowed as they are except the chewable tablets.  Compressed tablet(C.T.):  Uncoated and made by compression of granules.  Provide rapid disintegration and drug release.  Multiple compressed tablets(M.C.T.):  These tablets are prepared to separate physically or chemically incompatible ingredient or to produce prolonged action.  To avoid incompatibility, the ingredients of the formulation except incompatible material are compressed into a core tablet and  Then incompatible substance along with necessary excipients are compressed over previously compressed core tablet.
  • 6. Multilayered tablets :  Consist of two or more layers of materials compressed successively in the same tablets.  Colour of each layer may be same or different.  Tablets having layers of different colours are known as “Multicoloured tablets.”  Sustained action tablets :  Used to get sustained action of medicament.  These tablets when taken orally, release the medicament in sufficient qty as & when required to maintain the maximum effective concentration of the drug in blood throughout the period of treatment.  Enteric coated tablets:  These are compressed tablets meant for administration by swallowing and are designed to bypass the stomach & get disintegrated in the intestines only.
  • 7. Sugar coated tablets:  Compressed tablets having sugar coating are called “sugar coated tablets.”  Sugar coating is done to mask the bitter and unpleasant odour and the taste of the medicament.  Film coated tablet:  Having film coating of some polymer substance ,such as HPC,HPMC,EC.  Film coating protects the medicament from atmospheric effects.  Tablets generally tasteless, having less elegance than that of sugar coated tablets.
  • 8. Chewable tablet:  Tablets are chewed in the mouth and broken into smaller pieces.  In this way, disintegration time is reduced and rate of absorption of the medicament is increased.  B) Tablets used in oral cavity :  Buccal tablets :  Tablets are placed in buccal pouch or between gums and lips or cheek where they dissolve or disintegrate slowly & are absorbed directly without passing into the alimentary canal. e.g Tablet of ethisterone.  Sublingual tablets :  These tablets are placed under the tongue where they dissolve or disintegrate quickly and are absorbed directly without passing GIT. E.g Tablet of Glyceryl trinitrite
  • 9. Lozenges tablets and troches:  Tablets are designed to exert a local effect in the mouth or throat.  Used to treat sore throat or to control coughing in common cold.  They may contain local anaesthetics, antibacterial agents, astringents and antitussives.  Prepared by compression at a high pressure or by moulding process. Generally contain sweetening agent & flavouring agent.  Dental cones :  Minor compressed tablets meant for placing them in the empty sockets after tooth extraction.  They prevent multiplication of bacteria in the socket.  Tablet contains lactose, sodium bicarbonate & sodium chloride.
  • 10. C) Tablets administered by other routes  Implantation tablets:  Tablets are placed under the skin or inserted subcutaneously by means of minor surgical operation and are slowly absorbed.  These may be made by heavy compression but are normally made by fusion.  Mainly used for administration of hormones such as testosterone and deoxycorticosterone etc.  Vaginal tablets :  Tablets are meant to dissolve slowly in the vaginal cavity.  This tablet form is used to release steroids, antibacterial agents, antiseptics to treat vaginal infections.  Contains excipients such as, lactose or sodium bicarbonate.
  • 11. D)Tablets used to prepare solution  Effervescent tablets :  These tablets when added in water produce effervescence. So they dissolves rapidly in water due to chemical reaction .  These tablets are to be protected from atmospheric moisture during storage.  So ,tablets should stored in well closed air tight container.  Dispensing tablets :  Tablets to be added to a given volume of water to produce a solution of given concentration.  Contains excipients which gets dissolves quickly to form a clear solution.
  • 12. Hypodermic tablets  These are compressed tablets which are composed of one or more drugs with readily water soluble ingredients.  Tablets are dissolved in sterile water or water for injection and administered by parenteral route.
  • 13. Manufacturing of compressed tablets  Steps involves during manufacturing of compressed tablets:  I. Preparation of granule for compression:  a) Weighing of ingredients  b) mixing of powdered ingredients & excipients  c) converting the mixed ingredients into granule.  II. Compression of Granules into tablets.  III. Coating of tablets.  IV. Quality control of tablets.
  • 14. I.Preparation of granules for compression.  A) Weighing of ingredients:  Ingredients should weighed accurately using a balance of good quality.  B) Mixing of powdered ingredients and excipients .  The main objectives of this is to prepare a homogenous mass, so that uniform tablets can be manufactured.  C)Converting the mixed ingredients into granules:  The crystalline medicament can be compressed to get good quality compressed tablets.  In case the medicament along with excipients are in powder form it cannot be compressed as such into tablet Because :
  • 15. The granules can be prepared by following methods:  1. Moist granulation method:  2. Dry granulation  3. Granule by preliminary compression  1. Moist granulation method:  This is oldest and still most widely used method of tablet preparation.  The powdered and mixed tablet constituents are converted into moist coherent mass by wet screening .  This method involves following steps:
  • 16. Steps:  1. Milling of drugs and excipients.  2.Mixing of milled drugs and excipients.  3.Preparation of binder solution.  4.Mixing of binder solution with powder mixture to form wet mass( Granulation step).  5.This wet mass is then passed through Sieve no.8 or 10.  6.Drying the moist granules.  7.The dried granules are passed through Sieve number 20 to collect the granule of uniform size.  8.Then mixing of these dried granules with lubricating agent and disintegrating agent.  9.Granule are then ready to be compressed.
  • 17. Steps for wet granulation process  Weighing Mixing Granulation (wet mass)  Wet sieving  Drying Compression Mixing Granule dry sieving  (lubricant & disintegrant) (ready for  compression)
  • 18. 2. Dry granulation  There are certain medicaments which are available in crystalline form or in the form of granule having its own binding property.  Such medicament are passed through sieve No.20 or any other specified sieve .  And then mixed with any additional excipient.  This method is used for making tablet of aspirin, sodium bromide, potassium chlorate etc.
  • 19. 3. Granules by preliminary compression:  This method is also known as ‘slugging method’.  Method is used in those cases where the medicament is unstable in presence of moisture.  In this process the dry powder is compressed into large tablets or “slugs.”  These slugs are broken into small pieces which are passed through a specified sieves to collect the granules of suitable size.  A lubricating agent and disintegrating agents are mixed with these granules before compression into tablet machine.
  • 20. Excipients used in formulation of tablets:  An excipient is an inert substance which is added along with medicament to prepare the granules from the solid medicaments.  1. Diluents  2. Granulating agents  3. Binding agent  4.Disintegrating agent  5.Lubricants  6.Adsorbents  7.Colouring agents, flavouring agents & sweetening agent.
  • 21. 1.Diluent:  The diluents is needed in the formulation of a tablet, when the quantity of medicament in each tablet is very small and it is not possible to make a good tablet.  E.g.lactose,sucrose,sodium chloride,dextrose,and starch, mannitol,sorbitol,dibasic calcium phosphate dihydrate etc.  2.Granulating agents:  These are used to convert the fine powder into granules.  These agent provided proper moisture to convert fine powder into damp mass, after passing through a sieve of suitable number forms granules.  E.g water ,alcohol, mucilage of starch, mucilage of acacia, mucilage of tragacanth,gelatin solution, isopropyl alcohol, acetone etc.
  • 22. 3.Binding agents  These are used in granulation to provide proper strength to granules, in order to keep the tablet intact after compression.  E.g Gum acacia powder ,gum tragacanth, gelatin, sucrose, methyl cellulose etc.  4. Disintegrating agents:  The substance which are added in the tablet formulation to ensure disintegrating of the tablets into smaller particles when swallowed are called “Disintegrating agents.”  These are added into formulation of or oral tablets or sublingual tablets.  When the medicament is insoluble in water a disintegrating agent is needed.
  • 23. Disintegrating agents act in three ways:  I) By swelling :  Disintegrating agent gets swelled when it comes in contact with water or moisture e.g. Potato starch ,maize starch ,wheat starch , Methyl cellulose and Bentonite.  II)By producing effervescence:  They produce effervescence when they come in contact with moisture , e.g. sodium bicarbonate , citric acid and tartaric acid.  III)They melt at body temperature e.g Cocabutter.  The disintegrating agent is generally divided into two parts.  One part is mixed along with other excipients before the formation of granules.  Other part is mixed with dry granules before compression.
  • 24. 5. Lubricants:  These are added to improve the appearance of tablets, flow properties of granules & to prevent the sticking of the material to the dies and punches.  Lubricants are divided into three group:  i) Lubricants: Substance that reduce intergranular friction during compression and friction between tablet and die wall during the ejection of tablet.  E.g Talc, Magnesium stearate and calcium stearate etc.  ii) Glidants: They improve the flow properties of the granules from hopper to die of the tablet machine.  E.g. Talc, sodium chloride ,magnesium stearate ,boric acid, starch and calcium stearate etc.  Iii) Anti-adhesive agents : These prevent sticking of tablet surface to dies & punches during compression.  E.g liquid paraffin, mg stearate etc.
  • 25. 6.Absorbing agents:  These substances are used to absorb volatile oil, liquid extract and tincture etc. Which are included in the formulation of tablets.  E.g- mg carbonate ,kaolin and starch.  7. Colours, flavours and sweetening agents:  The colours are used to improve the elegance of the tablet.  Flavours are volatile oils and hence they are added into the granules just before compression of tablets.  Flavouring agents is dissolved in organic solvent and the solution is sprayed on the granules.  Sweetening agents are used to improve the taste of tablets.  These are used in lozenges & chewable tablets.  Sucrose, lactose and mannitol are some of the commonly used.
  • 26. II) Compression of Granules into Tablets:  The dried granules are compressed into tablets in a machine known as a tablet making machine .  The various type of machine :  1.Single punch tablet machine which may be hand operated or electrically operated.  2.Multipunch tablet machine  3.Rotary tablet machine  4.Dry cota tablet machine  In all these machine compression is achieved by filling the required qty of granules into dies and then compressing them in between the lower punch & upper punch .  Single punch is used for small scale mfg, whereas other machines are used for large scale mfg.  Rotary machine having about 70 sets of dies produce about 1200 tablets in one minute.
  • 27. 1.Single punch tablet machine:  Major parts :  A) Hopper shoe: To supply the granules to the die & remove the tablet after its compression.  B)Lower punch:  C)Upper punch:  D) Capacity regulator: To adjust the position of the lower punch to accommodate the required qty of granule by die.  E)Ejection regulator: to adjust the position of the lower punch ,so that its highest position is at par with surface of the die.  F) Die: It allows the lower punch and the upper punch to come close together to compress the granules.  G)Driving wheel: it helps in the movement of the lower punch, upper punch & hopper shoe & also check their movement.
  • 28.
  • 29. Working :  The cycle of movement of Tablet machine is as:  1. The upper punch rises to allow the hopper shoe to move over the disc.  2. The lower punch drops and granules feed from shoe into the die.  3.The shoe moves aside & the upper punch drops, thus compressing the granules into a tablet.  4. The upper punch rises upward and the lower punch rises upto the surface of the dies to eject the tablet.  5. The hopper shoe again moves forward over the dies, pushing aside the newly formed tablet.  The lower punch drops and the cycle is restarted.
  • 30. 2.Multi –punch tablet machine:  There are 2 to 12 dies on a big platform.  The number of punches depends upon the number of dies fixed to the platform. The working is similar to single punch machine but in this machine in one stroke as many tablets are compressed as the number of dies.
  • 31. 3. Rotary tablet machine :  A rotary tablet machine is used for large scale economic production.  In this machine about 1200 tablets are prepared in one minute.  There are 70 sets of dies and punches .  This machine has a circular rotating head, carrying a number of punch and dies assembles.  Head revolves continuously while the tablet granulation runs from hopper through feed frame & into dies .  There is uniform filling of the die due to this arrangement & therefore the tablets formed in rotary tablet machines have an accurate uniform weight.  Compression is done when upper and lower punches pass between pair of rollers.  The tablet comes out when the lower punch lifts up.
  • 32.
  • 33. 4. Dry cota tablet machine :  The machine is used for manufacturing of multi-compressed, multi-coloured and press-coated tablets.  In this machine two rotary machines work simultaneously by a single driven shaft.  The core tablet is prepared in one machine which is transferred to the second machine for compress coating.
  • 34. Manufacturing defects in tablets.  1. Capping :  In this case there is partial or complete removal of top or bottom portion of the tablet.  Reason for this effect:  Excessive fines in granules which entrap air in a tablet.  Defective punches and dies.  High speed of tablet machine .  The granules are too dry.  There is an usually high degree of compression.
  • 35. Defects can be removed by  Setting the dies and punches properly.  To reduce the percentage of fines.  Maintain desired moisture content level in granule.  Regulate the speed of tablet machine.  2. Picking and sticking :  Material is removed or picked up by the upper punch from the upper surface of the tablet.  In case of sticking ,the material sticks to the wall of the die.
  • 36. Reasons :  Use of worn out dies and punches.  Use of small qty of lubricants.  Presence of moisture in the granule.  Excess of powder in the granules.  Defects can be removed by:  A new set of die and punches.  A proper quantity of lubricants in the granules.  Dry granules.
  • 37. 3. Mottling :  Mottling means an unequal distribution of colour on the surface of a coloured tablets.  Reasons :  Migration of dye in the granules during the process of drying .  Use of different coloration of medicament and excipients.  Defects can be avoided by;  Drying the granule at low temperature.  Using the dye which can mask the colour of all the ingredients of tablet formation.
  • 38. 4. Weight variation:  During the compression of granules in a tablet machine , the tablets do not have a uniform weight.  Reasons;  Granules are not uniform in size.  Presence of excess amount of powder in granules.  No proper mixing of lubricants.  No uniform flow of granules from the hopper to the die.  5. Hardness :  Hardness depends on the weight of material &the space between the upper & lower punches during the stages of compression.  If volume of material varies or the distance between punches varies ,the hardness will also vary.
  • 39. 6. Double impression :  This defects occurs when the lower punch has a monogram or some other engraving on it.  During compression, the tablets receives an imprint of the punch.  Due to some defects in the machine, lower punch moves slightly upward before ejection of a tablet and gives a second, imprint on the tablet.  This can be removed by controlling the undesirable movement of the lower punch.
  • 40. III.Coating of tablets:  Purposes :  1.To mask the unpleasant taste and odour.  2.To improve the appearance of tablets.  3.To prevent the medicament from atmospheric effects.  4.To control the site of action of drugs (Enteric coating )  5.To produce the sustained released product.  Tablet coating generally done by  1. Pan coating  2.Press coating
  • 41. 1. Pan coating :  Coating is done in pan which is made up of copper/ stainless steel.  Pan is rotated with help of electric motor.  The tablet to be coated are placed in the pan.  Hot air is blown in.  Speed of pan is adjusted in such a way that tablet remain separated from each other in the pan.
  • 42. Cont..  After coating ,polishing is done in a polishing pan.  Pan coating is used for sugar coating ,film coating and enteric coating.  2. Press Coating:  In this technique the granules of coating material are prepared  & layer of coating material is placed on preformed tablet (below & above the tablet to be coated) in Drycota Rotary Tablet Machine.  The whole operation is carried out automatically in a number of steps.
  • 43. Sugar coating :  Sugar coating is done by pan coating method.  Various stages in the sugar coating process are:  1. Sieving 2.Sealing  3.Subcoating 4. Syrup coating  5.Finishing 6.Polishing  1. Sieving :  The tablets to be coated are shaken in a suitable sieve to remove the fine powder or broken pieces of tablet.
  • 44. 2.Sealing :  Sealing is done to ensure that a thin layer of water proof material, such as, shellac or cellulose acid phthalate is deposited on the surface of the tablet.  The shellac or cellulose acid phthalate is dissolved in alcohol or acetone.  The pan is rotated with the help of an electric motor.  There is arrangement of hot air to be supplied inside the coating pan.  The speed of pan is adjusted in such a way that the tablets remain separated from each in pan.  Nowadays ,it is done by fluidised bed coating or spray techniques.
  • 45. 3.Subcoating :  In subcoating ,several coats of sugar and other material, such as, gelatin, acacia etc. are given to round off tablet and to help in building up the tablet size.  After each addition of syrup dusting powder is sprinkled.  The dusting powder is a mixture of starch, talc and powdered acacia.  Dusting powder does not allow the tablet to stick together.  The hot air is blown inside the coating pan which is rotated at a suitable speed.
  • 46. Cont...  This ensure proper drying of the syrup coat.  The alternative addition of syrup and dusting powder is repeated until a coating of the required thickness is produced.  At end of process, warm syrup without dusting powder is used to obtain a smooth surface.
  • 47. 4.Syrup coating :  This is give sugar coats, opacity and colour to the tablet.  Several coats of the syrup are applied.  Colouring materials and opacifying agents are also added to the syrup.  The process of coating is repeated until uniform coloured tablets are obtained.
  • 48. 5.Finishing:  3 to 4 coats of syrup are applied in rapid succession without dusting powder and cold air is circulated to dry each coat.  This forms a hard smooth coat.  6.Polishing :  Beeswax is dissolved in volatile organic solvent and a few coat of it are given.  The finished tablets are transferred to a polishing pan which is rotated at a suitable speed so that the wax coated tablets are rubbed on the canvas cloth.  The polishing pan is rotated at a suitable speed so that the wax coated tablets are rubbed on the canvas cloth.  This gives a proper shining to the tablets.
  • 49. Film coating :  In this case the tablets are coated by a single or mixture of film forming polymers ,such as, HPMC, Carbowax, hydroxyethyl methyl cellulose, polyethylene glycol 400 etc.  The polymer is dissolved in some volatile solvent and is sprayed over the tablets in rotating pan.  The process is continued till uniform good film is formed over the tablet.  Film coating is also used to make the tablet water proof before the sugar coating .  Film coating can be enteric or non-enteric.
  • 50. Advantages:  It is less time consuming technique.  Not much labour required .  It has o adverse affect on disintegration of tablet.  The product cost is low because the material used for coating is quite cheap.  It protects the drug from atmospheric changes, such as light, air, and moisture.  Coating is resistant to cracking and chipping.  Tablet become elegant.
  • 51. Enteric coating :  Enteric coating is given to the tablet in order to ensure that these tablets will not disintegrate in the stomach but pass through it as they are.  Such tablets get disintegrated in the intestines.  Coating is done due to reasons:  Medicament produce severe irritation in the stomach.  The action of medicament is required in the intestine.  E.g anthelmintics and amoebicides are required to be absorbed from stomach.  Drug absorption is better in the intestines.  Delayed action is needed.
  • 52. Ideal properties:  Resistance to gastric fluids.  Non-toxic in the required quantity.  Economical.  Formation of a continuous film.  Compatible with drug on which coating is done.  On large scale, the enteric coating of tablets is done in a rotating pan.  Solution of enteric coating material such as, salol, cellulose acetate phthalate, shellac and its derivatives are prepared in a volatile organic solvent.  The solution is sprayed over the tablets which are rotated in the coating pan.
  • 53. Cont...  The hot air is blown into the pan which helps in the evaporation of organic solvent.  Hence , a fine film of enteric coated material is made over the tablet.  The process is repeated a number of times till required number of coatings are done.
  • 54. Microencapsulation  Microencapsulation is a process or technique by which thin coating can be applied to small particles of solids ,droplets of liquid or dispersion, thus forming microcapsules.  The microcapsules may consist of a single particle or clusters of particles.  It differs from other coating methods because microencapsulation process is used to coat the particles having a particle size range from several tenth of a micro to 5000 µ.
  • 55. Microencapsulation techniques :  1.Pan coating  2.Fluidised Bed coating  3.Coacervation  4. Electrostatic Deposition  5.Vacuum Deposition  6.Polymerisation  7.Multiorific centrifugal process.
  • 56. Pan coating :  This technique is suitable in those cases where the particle size is larger than 6000 µ.  The coating material is dissolved in a suitable volatile organic solvent and sprayed in the pan.  Hot air is circulated in the pan.  Fluidised bed coating :  Particle of solid core material are suspended in the turbulent current of air in a chamber.  The solution of coating material is prepared in the volatile solvent & atomised in the chamber thr nozzles.  Temperature is regulated in such a way that volatile solvent gets vaporised.
  • 57. Cont...  After coating ,the solid particles become quite heavy and fall on the screen near the outlet from where these can be removed .  Coacervation:  Coacervation means the separation of liquid or phase when solution of two hydrophilic colloids are mixed under suitable condition.  In this method , three immiscible phases of core material, solvent and coating material are formed followed by deposition of coating material on core.  The coating material is dissolved in a suitable solvent and the core material is uniformly dispersed in the soln of coating material.
  • 58. Electrostatic deposition  Method is useful both for solid particle and liquid droplets.  In this , core and coating material are electrically charged by means of high voltage such as 10,000 volts etc.  Core is charged and placed in coating chamber.  The coating material is also charged before it is sprayed as a mist.  Because charges are of opposite kind, the coating material gets deposited on the core due to electrostatic attraction.  Vacuum deposition :  Coating material is vaporised in a chamber under vacuum of the order of 10-2 to 10-5 mm, in which the core material is present.  The coating material gets deposited on the core particles.
  • 59. Polymerisation :  Core material is dispersed in a liquid or a gas in which monomeric units of coating material are present.  These monomers gets polymerised at the interface between the core particles and the liquid gas phase which form coats over the core.  Multi –orifice centrifugal process:  This is mechanical process for producing microcapsules.  The method is capable of microencapsulating liquid and solids.  The particles of the core material are forced through an envelope of coating material in solution by using centrifugal force.  This results in a mechanical microencapsulation of the core particles.
  • 60. Applications  It is used for masking the taste of bitter drugs.  It is used for preparing prolonged action of dosage form.  Used to separate an incompatible material.  Used to protect chemicals against moisture and oxidation.
  • 61. IV) Evaluation of tablets  1. Shape of tablets  2. Appearance  3. Content of active ingredient in tablets.  4. Uniformity of weight  5. Disintegration test for tablets  6. Dissolution test for tablets  7. Mechanical strength  8. Friability test
  • 62. 1.Shape of tablet  Shape of tablet as per pharmacopoeia is circular with flat or convex faces.  2. Appearance :  Coated tablet have a smooth and often coloured surface.  3.Content of active ingredient in tablet:  The amount of active ingredient in tablet is determined by doing the assay as stated in the monograph.  Generally 20 tablets in the monographs are used in the assay.  The result lies within the range for the content of active ingredient stated in the monograph.
  • 63. s
  • 64. Cont..  In such cases ,the limits specified in the monograph indicated in table.  The requirement of this table apply when the stated limit are between 90 to 110 percent .  4. Uniformity of weight :  Every individual tablet in batch should be uniform in weight, but a small variation in the weight of the individual tablet is liable to occur.  The following percentage deviation in weight variation is allowed.
  • 65. Cont...  Weigh 20 tablets selected at random & determine their average weight.  NMT 2 of individual weight may deviate from average weight .  And none should deviate by more than twice that percentage. Sr. no Average weight of tablet deviation Percentage 1. 80 mg or less 10 2. More than 80 mg & less than 250 mg 7.5 3. 250 mg or more 5
  • 66. 5. Uniformity of content:  Tablet must comply with requirement for uniformity of content specified in the individual monograph.  Percentage of medicament is calculated by doing assay for particular drug.  The variation in percentage of medicament per tablet is due to the following reasons:  1.Weighing of material before granulation  2.Variation in the weight of an individual tablet.  3.Error of random sampling  4. Analysis error  5.Purity of medicament.
  • 67. Cont..  As per the pharmacopoeia, 20 tablets are taken ,powdered and assayed .  The average weight of medicament present in each tablet is calculated which is then compared with desired weight.  The pharmacopoeia has prescribed the limit in percentage of medicament per tablet in the monograph.
  • 68. 6. Disintegration test for tablet:  Disintegration means to break the tablet into smaller particles after swallowing.  The time required to disintegrate the tablet is called “disintegration Time”.  The rate of disintegration is depends upon type of tablet.  The test of disintegration is required in tablet which are swallowed.  In general pharmacopoeia prescribed a limited of 15 minutes.
  • 69.
  • 70. Official disintegration test  The apparatus consist of :  A rigid basket-rack assembly supporting six cylindrical glass tube.  These tubes are held vertically by two superimposed transparent plastic plates with six holes having same diameter.  The upper and lower plates are held in position by vertical metal rod which is attached to mechanical device.  The assembly should be raised & lowered between 28 to 32 times per minute in liquid at 37 ºC
  • 71. Cont..  The tablets are kept immersed in the liquid within the tube by means of cylindrical guides discs.  The assembly is suspended in the liquid medium in a 1000 ml beaker .  The beaker may be filled in such a way that the wire mesh at the highest point is at least 25 mm below the surface of liquid and its lowest point is at least 25 mm above the bottom of the beaker.
  • 72. I) Method used for uncoated tablet:  Place one tablet in each of 6 tubes of basket, add disc to each tube & operate apparatus ,using water maintained at 37º ±2º .  At the end of 15 minute, lift the basket from liquid & observe the tablet.  Tablet pass the test if all size tablets have disintegrated.  In case one or two tablet fail to disintegrate ,repeat the test on 12 additional tablets.  The tablets pass test if NLT 16 of total of 18 tablet tested have disintegrate.
  • 73. II) Method used for coated tablet:  Place one tablet in each of the 6 tube of the basket,& if the tablet has soluble external coating ,immerse basket in water at room temperature for 5 min.  Then add disc to each tube & suspend in water maintained at 37 º ±2º C & operate the apparatus for 60 min.  The tablet pass the test if all the six have disintegrated.  In case any of tablets has not disintegrated, repeat the test on further 6 tablet replacing water with 0.1 N HCL.  Tablet then pass the test if all six tablet have disintegrated in acid medium.  If one or two fail ,repeat the test on 12 additional tablets.  Tab. Passes the test if NLT 16 of the 18 tablet tested get disintegrated.
  • 74. III) Method used for enteric coated tablets:  Place one tablet in a each of the six tubes of the basket and immersed basket in water for 5 min at room temp.  Operate apparatus without using disc for two hours. The basket is immersed in 0.1N HCL at 37º± 2º.  If no any tablet shows disintegration or cracks ,then add disc to each tube & operate the apparatus using phosphate buffer having pH 6.8 as immersion liquid at 37º± 2º.  After 60 min, remove assembly and observe the tablets.  The tablet pass test if all six tablets have disintegrated.  If one or two fail , repeat the test on additional 12 tablets.  The tablets pass the test if NLT 16 of the 18 tablets tested get disintegrated.
  • 75. 7.Dissolution test for tablet  The test is done for measuring the amount of time required for given percentage of the drug substance in a tablet to go into solution under specified condition in vitro.  Apparatus : consist of following parts:  1. A cylindrical covered vessel made of glass or other transparent material having 1000 ml capacity & vessel is fitted with lid having 4 holes ,one for having shaft of stirrer, second for placing thermometer and remaining two for removing sample.  2. An electric motor which is capable of rotating the basket in the vessel at varied speed between 25 and 150 RPM.
  • 76.
  • 77. Cont...  3. A cylindrical stainless steel basket made of woven wire cloth having an aperture size of 425 µm. The top of basket is attached to the disc on the driving shafter.  4.The vessel is equipped with suitable device for the withdrawal of samples of dissolution medium.  5. The vessel should be securely clamped in water bath maintained at 37º± 2º having an arrangement for smooth motion of water during the test.
  • 78. Method:  Place 1000 ml of water which should be free from dissolved air & previously warmed to 36.5º to 37.5º into vessel.  Place specified number of tablets in dry basket and set the apparatus.  Start the motor and adjust rotation speed to 100 rpm.  Withdraw the stated volume of solution from vessel after 45min.  Filter and determine the amount of active ingredient present in it.  Repeat the complete operation 4 times.
  • 79. Cont...  The tablet pass the test if for each of five tablets , the amount of active ingredient in solution is NLT 70 percent of the stated amount.  No –retesting is allowed.  8. Mechanical strength :  Pharmacopoeia has not fixed any standard for the mechanical strength or hardness of tablets.  The devices are commonly used to find out mechanical strength of tablet:  1. Monsanto hardness tester  2.Pfizer tablet hardness tester.
  • 80. 1.Monsanto hardness tester  The Monsanto chemical Co.ltd had designed spring pressure device to test the hardness of a tablet.  It has a graduated scale which gives the reading in kg/sq.cm.  The tablet to be tested is placed between the spindle and the anvil.  The desired pressure needed to hold the tablet in position is applied by moving the screw knob in clockwise direction.  The scale is moved so that the indicator is fixed at zero.  The pressure is then applied till the tablet breaks.  The reading is noted, which indicates the pressure which is needed to breaks the tablet.
  • 81. 2.Pfizer tablet hardness tester  It is bases on the principle of an ordinary plier.  Pfizer tablet hardness tester is plier fitted with a pressure dial.  The tablet is placed between the jaw of the plier and pressure is applied by pressing the handles with hand unit until tablet breaks.  The reading of the dial indicates the pressure needed to breaks the tablet.
  • 82.
  • 83. 9. Friability test:  Friability test is performed to evaluate the ability of teh tablet to withstand wear and tear in packing ,handling and transporting.  The apparatus used to perform this test is known as ‘Friabilator’.  Apparatus consist of :  Plastic chamber, which is divided into two parts and it revolves at a speed of 25 rpm.  20 tablets are weighed and placed in the plastic chamber.  The chamber is rotated for 4 minutes or 100 revolutions.  During each revolution the tablet falls from distance of 6 inch.
  • 84. Cont..  Loss in weight indicates the friability .  The tablets are considered to be good quality if the loss in weight is less than 0.8 %.