Tablet coating is the application of a coating material to the exterior of a tablet to confer benefits over uncoated tablets. Common purposes are to mask taste/odor, protect drugs from environmental factors or gastric acid, and control drug release. Major types are sugar coating, film coating, enteric coating, and press coating. Film coating involves spraying a polymer solution onto tablets while sugar coating is a multistage process including sealing, subcoating, smoothing, coloring and polishing. Standard pans and perforated pans are commonly used coating equipment.

1. TABLET COATING
PRESENTED BY : -- MS. PRAJAKTA PRUTHVIRAJ GURAV
M. PHARM (PHARMACEUTICS)

2. DEFINITION
• Tablet coating is the application of a coating material to the
exterior of a tablet with the intention of conferring benefits
and properties the dosage form over the uncoated variety.
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3. PURPOSE OF TABLET COATING
• Cover the unpleasant taste, odor and color.
• Physical and chemical protection in medicine from environment (light, moisture, and air).
• Control of drug release as in enteric coating or sustained release or more usually to coated
multi particulates.
• To protect drug from the gastric environment of the stomach with an acid-resistant enteric
coating.
• Improve the appearance of tablets.
• Assist and facilitate the identification of drug.
• Easing the process of blistering.
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4. TYPES OF TABLET COATING
• Sugar coating
• Film coating
• Enteric coating
• Press coating
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5. SUGER COATING
• Sugar coating is a multistage process and can be divided into the following steps:
1. Sealing of the tablet cores
2. Sub coating
3. Smoothing
4. Coloring
5. Polishing
1. Sealing/Water proofing: Provides a moisture barrier and harden the tablet surface.
• e.g. :Shellac, Zinc, Cellulose acetate phthalate (CAP), Polyvinyl acetate phthalate,
Hyroxypropylcellulose, Hyroxypropylmethylcellulose etc.
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6. 2. Subcoating: Causes a rapid buildup to round off the tablet edges.
Generally two methods are used for subcoating:
a) The application of gum based solution followed by dusting with powder and
then drying. This routine is repeated until the desired shape is achieved.
b) The application of a suspension of dry powder in gum/sucrose solution
followed by drying.
3. Grossing/Smoothing: It is specifically for smoothing and filing the
irregularity on the surface generated during sub coating. It also increases the
tablet size to a predetermined dimension.
4. Coloring: Gives the tablet its color and finished size.
5. Polishing: Produces the characteristics gloss. Polishing is achieved by
applying the mixture of waxes like beeswax, carnubawax, candelila wax or hard
paraffin wax to tablets in polishing pan. 8/20/2020 6

7. FILM COATING
• Involves spraying a solution of polymer + pigments + plasticizers on to a
rotated, mixed tablet bed forms a thin, uniform film on tablet surface.
• Coating suspension formulation:
• Typically this comprises:
1. Polymer
2. Plasticizer
3. Colorants
4. Solvent.
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8. IDEAL CHARACTERISTICS A FLIM COATING POLYMER
• Solubility: For conventional film coating the polymer should have good solubility in
aqueous fluids to facilitate the dissolution of the active ingredient from the finished
dosage form. However, where a modified-release action is required then a polymer
system of low water solubility or permeability will be chosen.
• Viscosity: Polymers should have a low viscosity for a given concentration. This will
permit the easy, trouble- free spraying of their solutions in industrial film coating
equipment.
• Permeability: Film coating can be used to optimize the shelf-life of a tablet
preparation, as some polymers are efficient barriers against the permeability of water
vapour or other atmospheric gases. These properties vary widely between the
individual polymers.
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9. PLASTICIZER
• Plasticizers are generally added to film coating formulations to modify the
physical properties of the polymer to make it more usable. One important
property is their ability to decrease film brittleness.
• Examples of plasticizers are:
• Polyols, such as polyethylene glycol 400
• Organic esters, such as diethyl phthalate
• Oils/glycerides, such as fractionated coconut oil. Ingeneral, only water-
miscible plasticizers can be used for aqueous-based spray systems.
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10. COLOURANTS
• Any permitted colorants in a film coat formula are invariably water-insoluble colors
(pigments).
• Pigments have certain advantages over water-soluble colors: they tend to be more
chemically stable
• towards light, provide better opacity and covering power, and optimize the
impermeability of a given film to water vapour.
• Examples of colorants are:
• • Iron oxide pigments
• • Titanium dioxide
• • Aluminum Lakes.
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11. SOLVENTS
• Modern techniques now rely on water as a polymer solvent because of the significant
drawbacks that readily became apparent with the use of organic solvents.
• The disadvantages of organic solvents for the process:
1. Environmental: the venting of untreated organic solvent vapor into the
atmosphere is ecologically unacceptable, and efficient solvent vapor removal from
gaseous effluent is expensive.
• 2. Safety: organic solvents provide explosion, fire and toxic hazards to plant
operators.
• 3. Financial: the use of organic solvents necessitates the building of flame- and
explosion-proof facilities. Ingredient cost is also comparatively high, and the
associated costs of storage and quality control must also be taken in to consideration.
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12. ENTERIC COATED TABLET
• This technique is used to protect the tablet core from disintegration in the acid
environment of the stomach for one or more of the following reasons:
• Prevention of acid attack on active constituents unstable at low pH.
• To protect the stomach from the irritant effect of certain drugs.
• To facilitate absorption of a drug that is preferentially absorbed distal to the stomach.
• Polymer are insoluble in aqueous media at low pH, but as the pH rises they
experience a sharp, well defined increase in solubility at a specific pH.
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13. PRESS COATING
• Use of compression to form coat around a pre-formed core.
Fig: Press coated tablet
• Used mainly to separate chemically incompatible materials.
• Also dual release patterns possible
• Compression coating is a dry process. 8/20/2020 13

14. MAJOR DIFFERENCES BETWEEN SUGER & FILM COATING
FEATURES FILM COATING SUGAR COATING
Appearance Retain contour of original core.
Usually not as shiny as sugar coat
type
Rounded with high degree
of polish
Weight increase because of
coating material
2-3% 30-50%
Logo or ‘break lines’ Possible Not Possible
Process stages Usually single stage Multistage process
Typical batch coating
time
1.5 to 2.0 Hours Eight hours but easily
longer
Functional coatings Easily adaptable for controlled
release
Not usually possible apart
from enteric coating
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15. TABLET COATING PROCESS
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16. COATING PROCESS
COATING COMPOSITION
IS APPLIED TO
MOVING BED OF TABLETS
HEATED AIR IS INTRODUCED
EVAPORATION OF THE SOLVENT
Tablet coating is
accomplished by the
movement of tablets in
Perpendicular or vertical
direction to the
application of the coating
composition
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17. COATING MACHINE
1=Inlet air, 2=Inlet air filter and air heater
3=Coating pan, 4=Compressed air,
5=Pneumatic spray 6=Outlet air
7=Container with pneumatic stirrer 8=Peristaltic pump
(Control pressure 5-6 bar, Atomizing air pressure 1-2 bar)
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18. 8/20/2020 18

19. EQUIPMENTS
• The Equipments used for the tablet coating are :-
1. Standard coating pan
2. Perforated coating pan
3. Fluidized bed coater
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20. A. STANDARD COATING PAN
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21. STANDARD COATING PAN
• It is also known as conventional pan system.
• Circular metal pan(mounted angularly on a stand.)
• 8-60 inches in diameter.
• 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 spraying the material
on to the rotating tablet bed.
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22. USE OF SPRAYING SYSTEMS
• Produces a faster, more even distribution of the solution or
suspension.
• Reduces drying time between solution application in sugar coating .
• Allows continuous application of the solution in film coating.
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23. • In standard coating pan ,the drying efficiency is
improved by:-
1.Pellegrini pan
2.The immersion sword
3.Immersion tube systems
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24. 8/20/2020 24

25.  Pellegrini pan-
• Baffled pan
• Diffuser(distributes the drying air uniformly over the tablet bed surface).
 IMMERSION- SWORD SYSTEM-
• 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 SYSTEM-
• 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
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26. B. PERFORATED PAN SYSTEMS
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27. PERFORATED PAN SYSTEMS
• Perforated or partially perforated drum.
• Rotated on its horizontal axis in an enclosed housing.
• The coting 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.
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28. PERFORATED PAN SYSTEM HAS
1. Accela-cota system
2. Hi coater system
3. Dria coater pan
4. Glatt coater
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29. 1. ACCELA - COTA SYSTEM
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30. 1. ACCELA COTA & HI COATER SYSTEM
• Drying air is directed in to the drum,
• Passed through tablet bed,
• Exhausted through perforations in drum.
2. 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.
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31. 2. DRIA COATER PAN
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32. 3. HI-COATER SYSTEM
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33. 4. GLATT COATER
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34. 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
• Exhausted out through an exhaust duct.
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35. C. 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 trough the center of the chamber.
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36. FLUID BED COATING MACHINE MECHANISM
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37. FLUIDIZED BED SYSTEM
• They then fall towards the chamber wall,
• Move downwards to reenter 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.
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38. SPRAY APPLICATION SYSTEM
• Two Basic systems used to apply a finely divided (atomized) spray of coating
solutions or suspensions on to tablet are-
I. High pressure, airless
II. Low pressure, air atomized
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39. I. AIR LESS SPRAY SYSTEM
• Liquid is pumped at high pressure{250-3000 pounds per square inch gauge(psig) },
• through a small orifice (0.009 inch to 0.020 inch) in the fluid nozzle Which results in a finely
divided spray.
• In this ,the degree of atomization & the spray rate are controlled by
a) Fluid pressure,
b) orifice size and
c) Viscosity of the liquid.
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40. II. LOW PRESSURE AIR- ATOMIZED SYSTEM
• Liquid is pumped through a somewhat large orifice (0.020 inch-0.060 inch in diameter ) at
relatively low pressure(5-50 psig)
• Low pressure air contacts with the liquid stream at the tip of the atomizer,& a finely divided
spray is produced.
• The degree of atomization is controlled by the
a) fluid pressure ,
b) Fluid cap orifice
c) Viscosity of liquid
d) Air pressure
e) Air cap design.
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41. FILM FORMING AGENTS
• The film forming agents tablet coating are classified into:
1.Non - enteric film formers
2.Enteric film formers
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42. NON-ENTERIC FILM FORMERS
• They are incorporated to give uniform film with desired mechanical strength which are as
follows:
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 (sodium carboxy methyl cellulose)
7. PG (propylene glycol)
8. ACRYLATE POLYMERS
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43. 1. HPMC-
• It is prepared by reacting alkali treated cellulose with methyl chloride with propylene
oxide.
• As it forms bridging & rough Tablet surface, it has to be mixed with other polymers
or plasticizers.
2. MHEC-
• 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, it is not used as frequently as HPMC.
• These polymers used in combinations with other polymers to modify film Properties.
• FOR EXAMPLE -
• Combinations of PG waxes with Cellulose acetate phthalate provide film that are
soluble in GI fluids.
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44. 3. EC-
• It is manufactured by the reaction of ethyl chloride with cellulose dissolved in NaOH.
• It is available in different viscosity grades.
• Unplasticized 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.
4. HPC-
• 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.
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45. 5. POVIDONE-
• 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.
6. ACRYLATE POLMERS-
• These are marketed under the trade Name of Eudragit.
• Eudragit RL & RS are copolymers of Acrylic and meth acrylic acid esters.
• These films produce pH independent, delayed actions.
• Preparation is similar to that of EC formulations.
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46. ENTERIC FILM FORMERS
• REASONS FOR ENTERIC FILM FORMERS-
• To protect acid-labile drugs from gastric fluid e.g. Enzymes & certain
Antibiotics.
• To prevent gastric distress or nausea due to irritation from the drug . e.g.,
Sodium salicylate.
• To deliver drugs intended for local Action in the intestines, e.g. Intestinal
antiseptics.
• To deliver drugs that are optimally Absorbed in the small intestine to their
primary absorption site.
• To provide a delayed-release component for repeat-action tablets.
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47. PROPERTIES OF AN IDEAL ENTERIC COATING
MATERIAL
• 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, nontoxicity, with low cost.
• Ease of application without Specialized equipment.
• Ability to be readily printed and allow film to be applied to debussed tablets.
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48. ENTERIC FILM FORMERS
• CAP(Cellulose acetate phthalate)
• ACRYLATE POLYMERS
• HPMCP( Hydroxypropyl methyl cellulose phthalate)
• PVAP(Polyvinyl acetate phthalate)
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49. 1.CAP
• 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 a average particle size of 0.2 microns.
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50. 2. ACRYLATE POLMERS
• 2 forms of commercially available Enteric acrylic resins are
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.
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51. 3. HPMCP
• 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.
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52. 4. PVAP
• 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.
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53. COATING COMPOSITION
• 1. Solvent
• 2. Plasticizers
• 3.Colorants
• 4.Opaquant-extenders
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54. 1.SOLVENT
• 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)
• It should be Colorless, tasteless, odorless, Inexpensive, nontoxic, inert and
Noninflammable and rapid drying Rate.
• Examples- Water, Ethanol, Methanol, Isopropanol, Chloroform, Acetone,
Methylene chloride , Methylene ethyl ketone.
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55. 2. PLASTICIZERS
• 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
• e.g., Polysorbate(tweens),sorbitan esters(spans), organic acid esters.
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56. 3.COLORANTS
• 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 opaquqnt extenders
• 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.
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57. • The inorganic materials and the natural colorants are-
• Iron oxides, Caramel, Carotenoid, Chlorophyll, indigo, Flavones, Turmeric and
carminic acid.
• A variety of products that are Commercially available are-
• Opalux- Opaquqnt color concentrate for sugar coating.
• Opaspray -for film coating.
• Opadry- complete film coating concentrate.
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58. 4. OPAQUANT-EXTENDERS
• 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:-Titaniundioxide
• Silicates like (Talc, Aluminium silicate)
• Carbonates like-magnesium carbonate,
• Sulphates like calcium sulphate
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59. DEFECTS IN COATING
• Sticking and picking
• Roughness
• Orange peel
• Color variation
• Cracking
• winning
• Capping
• Lamination
• Blistering 8/20/2020 59

60. STICKING AND PICKING
• Over wetting or excessive film thickness causes tablets to stick and piece of
film may remain adhere to pan or tablet. i.e “picking”
• Remedies:
Reduction in liquid application rate.
Increase in drying air temperature and air volume.
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61. ROUGHNESS:
• A rough or gritty surface observed when the coating is applied by spray.
• Causes : Some of the droplets may dry too rapidly before reaching the tablet
bed and deposits on tablet surface.
• Remedies :
Moving the nozzle closer to the tablet bed.
Reducing the degree of atomization can decrease the roughness due to spray
drying.
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62. ORANGE PEEL
• Inadequate spreading of coating solution before drying causes a bumpy or
Orange –peel effects on the coating
• Causes : Indicates that spreading is impaired by rapid rate of drying or by high
solution viscosity.
• Remedies : Thinning of coating solution with additional solvents may correct
this problem.
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63. COLOUR VARIATION
• Colour variation Problem caused by or the formulation Improper mixing,
uneven spray pattern and insufficient coating may results in color variation.
• Remedies : Proper mixing of coating solution
• Spray uniformly
• Use of lake dyes eliminates dye migration.
• A reformulation with different plasticizer and additives is the best way to solve
film instability.
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64. Cracking :
• Cracking occurs if internal stresses in the film exceed the tensile strength of
the film. The tensile strength of the film can be increased by using higher
molecular –weight polymers or polymer blends.
• Remedies: Adjusting the plasticizer types and concentration can minimize
internal stresses Also adjusting the pigment types and concentration can
minimize internal stresses
Blistering :
• Evaporation of solvents from the core in the oven. And effect of high
temperature on the strength, elasticity and adhesion of the film may results in
blistering.
• Remedies : Controlled drying conditions.
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65. • Twinning:
• Two or more tablets are stick together.
1. Unbalancing the pan speed.
2. Hi spray rate.
Fig: Twinning effect
• Remedies: This problem can be solve by balancing the pan speed and spray
rate
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66. IDEAL CHARACTERISTICS OF COATED TABLETS
• Film-coated tablets must comply with the uniformity of mass test unless otherwise
justified and authorized
• Film-coated tablets comply with the disintegration test.
• Film-coated tablets should display
• An even coverage of film and colour.
• No scraping of tablet edges or crowns.
• Logos and break lines should be distinct and not filled in.
• The tablet must also be within specifications.
• Tablets must comply with finished product specifications
• Sugar-coated tablets should ideally be of a perfectly smooth rounded contour with even
colour coverage and polish to a high gloss.
• Any printing should be distinct, with no broken print. 8/20/2020 66

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