Tablet coating by ankita yagnik

Prepared by: Ankita Yagnik
Assistant Professor
Akshar-Preet Institute of Pharmacy,
Jamnagar

 Coated tablets are defined as tablets
covered with one or more layers of mixture
of various substances such as natural or
synthetic resins, gums, sugar, plasticizers,
coloring and flavoring material.
 Tablet coating is the last critical step in the
tablet production cycle.
2

Mainly there is three objectives of coating
 Therapy
Avoid irritation of oesophagus and stomach
Avoid bad taste
Avoid inactivation of drug in the stomach
Improve dug effectiveness
Prolong dosing interval
Improve dosing interval
Improve patient compliance
3

 Technology
Reduce influence of moisture
Avoid dust formation
Reduce influence of atmosphere
Improve drug stability
Prolong shelf life
 Marketing
Avoid bad taste
Improve product identity
Improve appearance and acceptability
4

 It involves the application of
sugar solution with color for
several times to give
UNIFORM AND ELEGANT FILM.
The coating is water soluble
and dissolves after
swallowing.
 ADVANTAGES:
 It prevents unpleasant odor.
 Give sweet taste to tablet by
masking bitter taste.
 Highly elegant and glossed
tablets are obtained.
6

 The tablet having deep convex surfaces with
thin rounded edges are suitable for sugar
coating.
 In sugar coating, the tablet should be
resistant to breakage, chipping and
abrasions.
 Because sugar coating tends to be long and
vigorous.
Sugar coating involves following steps;
 Sealing/ Water proofing
 Sub-coating
 Syruping (smoothing)
 Finishing
 Polishing
7

 Prior to sugar coating the tablets core must
be sealed, dried and free from any residual
solvents.
 It prevents moisture penetration in to the
tablet core.
 Seal coating agents-shellac, zein, Oleicacid,
PG, PEG4000, alcohol, methylene chloride.
 Zein is alcohol-soluble protein derivative.
 Shellac is more effective(because of
polymerization of shellac), But it lengthens
tablet disintegration and dissolution times
8

 It is the actual starting of coating process
and provides the rapid buildup. It also acts as
the foundation for smoothening and polishing
 Sub coating is applied;
To form uniform edges.
To build up the tablet size.
 Sub coating increases the tablet weight from
50 to 100 percent.
 Examples-Gelatin, sugarcane powder, corn
syrup, distilled water, Gum acacia.
9

 Generally two methods are used;
 1) The application of gum based solution
followed by dusting with powder and then
drying. This process is repeated until desired
shape is achieved.
 2) The application of suspension of dry
powder in gum/sucrose solution followed by
drying.
10

 It is done to cover the imperfections in the
Tablet surface caused during sub coating
step.
 It involves-
 Application of syrup coating with grossing
syrups followed by the addition of dilute
colorants to provide tinted base.
 In subsequent steps, the syrup solution
containing dye are applied until final size
and Color is achieved.
 In final step a clear syrup coat without dye is
applied.
11

 No color is added until the tablets are quit
smooth,
 Premature application to the rough tablets
can produce a Mottled appearance in the
final coated tablets.
 Syrup coating constituents-
 colorant ,
 sub-coating powder ,
 calcium carbonate ,
 Sugar cane powder,
 corn starch,
 syrup ,
 distilled water.
12

 The desired luster to the tablet is obtained
by polishing .
 Tablets are polished in a Standard coating
pans by application of carnauba wax(yellow),
bees wax(white),paraffin wax (Or) warm
solutions of waxes in naphtha (or) suitable
volatile solvent.
13

 It is more favored over sugar coating.
 Film coating is deposition of a thin film of
polymer surrounding the tablet core.
 The polymer is solubilized into solvent then
other additives like plasticizers and pigments
are added.
 Resulting solution is sprayed onto a tablet
bed and then drying process is carried out
giving thin deposition of coating material
around each tablet
14

 It should be soluble in a solvent of choice.
 It must produce an elegant coat.
 It should be stable in presence of heat, light
or moisture.
 It should not possess disagreeable
(unpleasant) color, taste or odor.
 It should be non-toxic and pharmacologically
inert.
 It should be compatible with coating
additives.
15

 This type of coating is used to protect tablet
core from disintegration in the acid
environment of the stomach for one or more
of the following reasons;
• 1) To prevent degradation of acid sensitive
API
• 2) To prevent irritation of stomach by certain
drugs like sodium salicylate
• 3) Delivery of API into intestine
• 4) To provide a delayed release component
for repeat action tablet
16

 Enteric layer system of two types;
1. One layer system: The coating formulation
is applied in one homogeneous layer, which
can be whites-opaque or coloured.
2. Two layer system: To prepare tablet of
high quality and pleasing appearance the
enteric formulation is applied first followed
by coloured film.
Both layers can be of enteric polymer or
only the basic layer contains enteric
polymer while top layer is fast
disintegrating and water soluble polymer.
17

 Resistance to gastric fluids.
 Susceptibility or permeability to intestinal
fluids.
 Compatibility with most coating solution
components & the drug substrates.
 Stability alone and in coating solution.
 The film should not change on aging.
 Formation of a continuous film with low cost.
 Ease of application without Specialized
equipment.
 Ability to be readily printed.
18

 1. Enteric sugar coating:
 Enteric polymers are included in sealing
stage and other steps are followed as
conventional tablets.
 2. Enteric film coating:
 Enteric polymers are used for direct film
coating process.
19

 Polymers like modified acrylates, water
insoluble cellulose (EC) etc. are used for
controlled release coating rest of the process
remains same as enteric coating.
20

 A) Electrostatic coating:
 This type of coating is also known as powder
coating.
 Electrostatic coating/powder coating is a dry
finishing process, using fine particles of
paint, which are electro-statically charged
are sprayed onto a work piece.
 Once the powder is applied, the part is
cured, causing the powder to adhere to the
surface.
21

 B) Vacuum film coating:
 It is new coating technique that employs
specially designed baffled pan. The pan is
hot and water jacketed and it can be sealed
to achieve a vacuum system.
 The tablets are placed in pan and the air in
the pan is displaced by nitrogen before the
desired vacuum level is obtained. The
coating solution is applied by airless spray
system.
 The vapors of the evaporated solvents are
removed by vacuum system. Organic solvents
can be effectively used with this coating
techniques and high environment safety is
also there.
22

 C) Compression coating:
 Compression coating is not widely used, but
it has advantages in some cases in which the
tablet core cannot tolerate organic solvents
or water and yet needs to be coated for
taste masking, or to provide delayed or
enteric properties to the product.
 In addition incompatible ingredients can be
conveniently separated by process. This type
of coating requires a specialized tablet
machine.
23

 D) Dip coating:
 Coating is applied by dipping them into
coating liquid the wet tablets are dried in
conventional coating pans.
 Alternate dipping and drying steps may be
repeated several times to achieve the
coating of desired one.
 The process lacks the speed, versatility, and
the reliability of spray coating techniques.
24

 1. Film formers (Enteric/Non-enteric)
 2. Solvents
 3. Plasticizers
 4. Colorants
 5. Opaquant-extenders
 6. Miscellaneous
25

 1. HPMC(Hydroxy propyl methyl cellulose)
 2. MHEC(Methyl hydroxyl ethyl cellulose)
 3. EC(Ethyl cellulose)
 4. HPC(Hydroxy propyl cellulose)
 5. POVIDONE
 6. SCMC
 7. PEG
26

 It is available in different viscosity grades.
 It is prepared by reacting alkali treated
cellulose with methyl chloride with
propylene oxide.
 When used alone it forms bridging & rough
Tablet surface(due to debossing of tablet), it
has to be mixed with other polymers or
plasticizers.
 It is cheap, flexible, highly resistant to heat
and moisture, no taste, no odor.
27

 It is available in different viscosity grades.
 It is prepared by reacting alkali treated
cellulose with methyl chloride & then with
ethylene oxide.
 It has similar properties as that of HPMC, But
it is soluble in fewer organic solvents, so it is
not used as frequently as HPMC.
 These polymers used in combinations with
other polymers to modify film Properties.
28

 Depending upon the degree of ethoxy substitution
different viscosity grades are available.
 It is manufactured by the reaction of ethyl-chloride
with cellulose dissolved in NaOH.
 Un-plasticized EC forms brittle films & requires
film modifiers to obtain acceptable film.
 It is water insoluble & thus Cannot be used alone
for tablet coating.
 It is usually combined with water Soluble additives
 E.G.- HPMC to prepare film with reduced water
soluble Properties &This combinations are widely
Used in sustained release coating.
29

 It is manufactured by the treatment of
cellulose with NaOH followed by the reaction
with propylene oxide at Elevated
temperature and pressure.
 It forms tacky films.
 Used in combinations with other polymers to
improve film characteristics.
 It is soluble in water (below 40 ͦ c & insoluble
above 45°𝒄) ,GI fluids & in many polar
Organic solvents
30

 Degree of polymerization decides molecular
weight of material. Based on viscosity
available in different grades.
 It is synthetic polymer consisting of linear
1-vinyl-2-pyrrolidinone groups.
 It gives clear, glossy, hard films when dry.
 It give tacky films which can be overcome by
plasticizer or other polymer.
31

 It is available in medium, high and extra high
viscosity grades.
 It is easily dispersed in water to form
colloidal solution but it is insoluble in most
organic solvents and hence not a material of
choice for coating solution.
 It give tacky films.
32

 Lower molecular weights PEG(200-600) are
liquid at room temperature and are used as
plasticizers.
 High molecular weights PEG(900-8000) are
white, waxy solids at room temperature
33

 CAP(Cellulose acetate phthalate)
 ACRYLATE POLYMERS
 HPMCP(Hydroxypropyl methyl cellulose
phthalate)
 PVAP(Polyvinyl acetate phthalate)
34

 It is widely used.
 As it is hygroscopic and relatively permeable
to moisture and gastric Fluids.
 Film formed are brittle and hence
formulated with hydrophobic- Film forming
materials to achieve better enteric films.
 Aquateric coating is a reconstituted
colloidal dispersion of latex particles.
 It is Composed of solid or semisolid polymer
spheres of CAP ranging in size from 0.05-3
microns with an average particle size of 0.2
microns.
35

 These are marketed under the trade Name of Eudragit.
 2 forms of commercially available,
 Eudragit L and Eudragit S.
 Eudragit l is available as an organic Solution, solid or
aqueous dispersion.
 Eudragit s is available only as an organic solution and
solid.
 Eudragit l & S are soluble in intestinal Fluid at pH 6&7.
 Eudragit L & S are copolymers of Acrylic and meth acrylic
acid esters.
 These films produce pH independent, delayed actions.
 Preparation is similar to that of EC formulations.
36

 It is derived from HPMC by esterification with
phthallic anhydride.
 These are stable than cap and dissolve at
lower pH compared to cap and acrylate
polymers.
 The solubility characteristic may result in
Higher bioavailability of some specific drugs.
 It is available in various grades- HP55,HP50
etc.
37

 It is manufactured by the esterification of
partially hydrolyzed Polyvinyl alcohol with
phthallic Anhydride.
 It is similar to HPMCP(HP55) in stability and
pH dependent solubility.
38

 It is to dissolve or disperse the polymers and
other additives and convey them to the
substrate surface.
 The ideal requirements of the solvent are
 It should either dissolve or disperse the polymer
system.
 It should have no environmental impact.
 It should easily disperse other coating solution
components in to the solvent system.
 It should have rapid drying rate(ability to coat
300kg load in 3-5 hours)
39

 It should be
 Colorless,
 tasteless,
 odorless,
 Inexpensive,
 nontoxic,
 inert and Noninflammable
 Should have rapid drying Rate.
 Examples-
Water, Ethanol, Methanol, Isopropanol,
Chloroform, Acetone, Methylene chloride ,
Methylene ethyl ketone.
40

 It is used to modify the quality of the film .
 Plasticizing techniques involve internal plasticizers
and external plasticizers.
 Internal plasticizers involves Chemical modification
of the basic polymer that alters the physical
properties of the polymers.
 Chemical plasticizers Additives of the Coating
solution to achieve the desire effect of the film
(flexibility ,tensile Strength, adhesive properties).
 Level of plasticizers ranges from 1-50% by weight of
film former.
 Examples: Castor oil, Propylene glycol, Glycerin,
Surfactants
41

 It is to provide the distinct color and
Elegance to the dosage form.
 To achieve the proper distribution of
suspended colorants in the coating solutions
requires Use of fine powdered colorants (<10
microns)
 The concentration of colorants in the coating
solution depends on the color shade, desired
the type of dye and the concentration of the
opaqunt extenders
42

 For very light shade conc. Lt 0.01%
 For dark shade Conc. Mt 2.0% is required.
 The most common colorants in use are certified
by FOOD DRUG AND COSMETICS (FD&C) or DRUG
AND COSMETIC (D&C) Colorants.
 These are lakes and dyes. Lakes are derived
from dyes by precipitating with carriers e.g.,
Alumina or talc.
 The inorganic materials and the natural
colorants are- Iron oxides,Caramel, Carotenoid,
Chlorophyll, indigo, Flavones,Turmeric and
carminic acid.
43

 A variety of products that are Commercially
available are-
 Opalux- Opaquant color concentrate for
sugar coating.
 Opaspray -for film coating.
 Opadry- complete film coating concentrate.
44

 These are very fine inorganic powders used
In the coating solution formulation to provide
more pastel colors and increase film
coverage.
 Provide white coating or mask the color of
the tablet core.
 Examples-
 Titanium dioxide,
 Silicates like (Talc, Aluminiumsilicate),
 Carbonates like-magnesium carbonate,
 Sulphates like calcium sulphate.
45

 1. Conventional/Standard coating pan system:
 Circular metal pan having 8-60 inches in
diameter mounted angularly on a stand.
 It is rotated on its horizontal axis by a motor.
 Heated air is directed into the pan & on to the
tablet bed surface and is exhausted by means
of ducts through the front of the pan.
 Coating solution are applied to the tablets by
ladling or spraying the material on to the
rotating tablet bed.
47

 In standard coating pan ,the drying efficiency is
improved by:-
 Pellegrini pan:
 Baffled pan
 Diffuser(distributes the drying air uniformly over the
tablet bed surface).
 The immersion sword:
 Perforated metal sword device immersed in the tablet
bed.
 Drying air is introduced through this device and flows
upward from the sword through the tablet bed.
 Immersion tube systems:
 Tube immersed in the tablet bed.
 Tube delivers the heated air.
 In immersion tube system the coating solution is
applied with the heated air from the immersed tube
49

 2. Perforated pan system:
 It is perforated or partially perforated drum.
 Rotated on its horizontal axis in an enclosed
housing.
 The coating solution is applied to the surface
of the rotating bed of tablets through
spraying nozzles, which are present inside
the drum.
 Perforated pan coaters are efficient drying
systems with high coating capacity.
51

 PERFORATED PAN
SYSTEM HAS-
 Accela-cota system
and Hi coater system
• Drying air is directed
in to the drum,
• Passed through tablet
bed,
• Exhausted through
perforations in drum.
53

 Dria coater pan
• Drying air enters through hollow perforated
ribs located on inside periphery of the drum.
• As the coating pan rotates, the ribs dip into
the tablet bed and drying air passes up
through Exhaust is from the back of pan.
54

 Glatt coater:
• It is the latest perforated pan coater to be
introduced in the industry.
• In this, drying air can be directed from inside
the drum through tablet bed and exhausted
out through an exhaust duct.
55

 3. Fluidized bed system:
 In this system fluidization of the tablet mass is
achieved in a columnar chamber by the upward flow
of drying air.
 The air flow is controlled, so that more air enters
the center of the column, causing the tablets to rise
in the center.
 The movement of tablets is upward through the
center of the chamber.
 They then fall towards the chamber wall, Move
downwards to re-enter the air stream At the bottom
of the chamber.
 Coating solutions are applied from a spray nozzle
which is located at the bottom of the chamber or
are sprayed onto the top of the Cascading tablet
bed by nozzles located in the upper region of the
chamber.
56

 Determination of the quality of a tablet coat
involves studying of the film and the film-
tablet interactions. The following test
methods can be employed;
 Adhesion test with tensile strength testers
are used to measure the force needed to
peel the film from the tablet surface.
 Diametric crushing strength of the coated
tablets is determined using a tablet hardness
tester.
 The rate of coated tablet disintegration and
dissolution should also be studied.
58

 Exposure to elevated humidity and
measurement of tablet weight gain provide
relative information on the protection
provided by the film.
 Stability studies can be conducted on coated
tablets to verify whether temperature and
humidity changes would result in film defects.
 Determination of film surface roughness,
hardness and color uniformity.
 Resistance of coated tablet to abrasion is
done by merely rubbing the coated tablet on
white paper sheet. Film should remain intact
and no color transferred to paper.
59

 Picking and sticking:
 This defect is occurs when the coating removes
a piece of the tablet from the core. It is caused
by over-wetting the tablets, by under-drying, or
by poor tablet quality.
 Bridging:
 This occurs when the coating fills in the
lettering or logo on the tablet and is typically
caused by excess application of the solution,
poor design of the tablet embossing, high
coating viscosity, high percentage of solids in
the solution, or improper atomization pressure.
61

 Erosion:
 This can be the result of soft tablets, an over-
wetted tablet surface, inadequate drying, or
lack of tablet surface strength.
 Twinning:
 This is the term for two tablets which stick
together, and it’s a common issue with capsule
shaped tablets. If you don’t want to change the
tablet shape, you can solve this problem by
changing the pan speed and spray rate.
 Try lowering the spray rate or increasing the
pan speed.. The change is almost impossible to
see, but it solves the twinning problem.
62

 Peeling and frosting:
 This is a defect where the coating peels away
from the tablet surface in a sheet. Peeling
indicates that the coating solution did not lock
into the tablet surface.
 This could be due to a defect in the coating
solution, over-wetting, or high moisture
content in the tablet core.
 Blistering:
 Too rapid evaporation of solvent from the
coated tablets and the effect of high
temperature on the strength and elasticity of
the film may cause blistering. Milder conditions
are required in this case.
63

 Mottled color:
 This can happen when the coating solution is
improperly prepared, the actual spray rate
differs from the target rate, the tablet cores
are cold, or the drying rate is out of spec.
 Orange peel
 This refers to a coating texture that resembles
the surface of an orange. It is usually the result
of high atomization pressure in combination
with spray rates that are too high
64

 Capping:
 The main cause of this defect is improper
compression of the tablet. This defect will
not be revealed unless the coating is
initiated. This defect occurs due to excessive
drying in pre-heating stage.
 Chipping:
 Chipping is caused due to high pan speed, a
friable tablet core or coating solution that
lacks good plasticizer.
65

Picking and
sticking
Orange peel
66

Capping
and
Lamination
Roughness
67

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