This document provides information on the tablet coating process. It defines tablet coating as applying a coating material to the external surface of a tablet core. The main objectives of tablet coating are to mask unpleasant tastes/odors, control drug release, provide physical/chemical protection, and improve appearance. Film coating is the most common coating method and involves spraying a coating solution onto rotating tablets and drying. Key considerations for the coating process include the coating materials used, equipment selection, and process parameters. Common coating defects and their causes are also discussed.

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2. Department Of Pharmaceutics
Roshaan Raihan
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Tablet Coating Process

3. Definition
3
 Tablet coating is defined as a technique of applying coating
material to the external surface of the tablet core.
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PRINCIPLE
 Tablet Coating is the process of a
coating composition to a moving
bed of tablets with the concurrent
use of heated air to facilitate
evaporation of solvent .

4. 4
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5. History
5
• One of the oldest arts in pharmacy
• To mask unpleasant taste or odor of drug
• Coating of pills in France (17 century)
• Coating of pills with syrup in France (19 century)
• In the mid 20s pills were substituted by compressed tablets
• First Film Coating tablet (Abbott)
• Use of fluidization in coating (1953-1959)
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6. objectives of tablet coating
6
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To mask the unpleasant taste and odour of the drug.
To control release of drug from the tablet (control
release).
To offer a physical and/or chemical protection to the
drug.
To minimize the product damage
due to physical stress.
O2
CO2
LIGHT
H20

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To protect stomach from adverse effect of some drug.
To protect drug from the gastric environment of the
stomach.
To improve pharmaceutical elegance by use of special
colors.
Improving product appearance and helping in brand
identification.
Masking batch differences in the appearance of raw
materials.

8. Specification of Tablet for coating
8
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 Clear of dust & additional particles.
 posses proper physical characteristics.
 Resistant to abrasion and chipping.
 Should have smooth surface & proper shape.
 Must be in constant motion during drying phase.
 Physico-chemical properties of formulation
should be consider.

9. Types of tablet coating
9
 Main types of coating are:
1. Film Coating
2. Sugar Coating
3. Press Coating
4. Functional Coating
 Specialized coating process are:
 Dip coating
 Electrostatic coating
 Vacuum Film Coating
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10. 1. Film Coating
10
 Modern approach to coating tablets, capsules, or pellets by
surrounding them with a thin layer of polymeric material.
Process: Single stage process, which involves spraying a
coating solution or suspension.
 The solution is sprayed onto a rotating tablet bed followed
by drying, which facilitates the removal of the solvent
leaving behind the deposition of thin film of coating
materials around each tablet.
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12. Advantages of film coating
12
 Single step process & relatively short period of time.
 Minimal weight increase (2–3%)
 The film is very thin.
 Engravings are possible on tablet surface
 Better mechanical strength is obtained.
 The cost of the film coated tablets is less.
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13. Disadvantages of film coating
 Using organic solvent
‾ flammable
‾ toxic & health hazardous
‾ relatively expensive
 They don’t have elegance as that of the sugar coated tablet.
 Their consumer appeal is less compared to sugar coated
tablet because of their tasteless nature.
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Types of film coating
Rapidly disintegrating
film coating
Taste masking film
coating
Modified-release film
coating
Extended release
(Sustained or controlled
release coating)
Delayed release
Enteric film coating

14. Film coating equipments
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1. Coating pan 2. Fluidized bed coating

15. 1. Coating pan
 Coating solution variables
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 Process variables

16. Types of coating pan
16
1.Standard coating pan
 Conventional pan
 Pellegrini pan
 Immersion sword & Immersion tube system
2.Perforated pan system
 Accela cota pan
 Hi-coater pan
 Dria coater pan
 Glatt coater pan
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17. Standard Coating Pan
Immersion-
tube system
17
Pellegrini pan
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Immersion
sword system

18. Perforated pans
18
Accela cota
system
Hi-coater
system
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19. 19
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Dria coater system
Glatt coater system

20. 2. Fluidized bed coating
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21. 2. Fluidized bed coating
21
 In fluid bed coating, particles are fluidized, coating fluid is
sprayed on and dried.
 Applying Film Coating to tab, pellets, granules and
powder.
 Highly efficient drying system.
 According to the spraying patterns fluid bed equipment
can be classified to:
1. Top spray coating
2. Bottom spray coating
3. Tangential coating
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22. 22
Three basic process used for fluid-
bed film coating

23. Spray application systems
1. Airless or hydraulic spray system
 Liquid pumped at high pressure (250-3000 psig) through
small orifice, fine spray.
 Suitable for large scale Film Coating.
 Degree of atomization depends on:
 Fluid pressure
 Orifice size
 Viscosity of liquid
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1. Airless or hydraulic spray system
2. Air spray or pneumatic system

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2. Air spray or pneumatic system
 Liquid pumped through large orifice.
 Low pressure (5-50 psig).
 Suitable for small scale operation & aqueous Film Coating.
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25. Formulation of film coating
25
Ideal characters of coating material
 Solubility in the coating solution.
 Capacity to provide elegant looking dosage.
 Stability in presence of water , heat & moisture.
 Compatibility with other additives.
 Non-toxic and easy to apply.
 Should form resistance against cracking.
 No bridging should occur.
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Plasticizer Colorant
Polymer
(Film former)
Solvent
Miscellaneous
agents

26. 1. polymer
26
The polymer is the major ingredient, Consequently, this
material will have the greatest impact on the final properties
of the coating.
Ideal characteristics of a film coating polymer:
1. Solubility
 For conventional film coating the polymer should have good solubility
in aqueous fluids.
 However, where a modified-release action is required then a polymer
system of low water solubility or permeability will be chosen.
2. Viscosity
 polymers should have a low viscosity for a given concentration.
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3. 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 vapor or other atmospheric gases.
4. Mechanical properties
 Must have adequate strength to withstand the impact and abrasion
encountered in normal handling.
 Insufficient coating strength will be demonstrated by the development
of cracks and other imperfections in the coating.
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Polymers used in immediate release coating
Class Example Solubility
1. Cellulose derivatives
HPMC :
 It is readily soluble in aqueous
media.
 Form film with good mechanical
properties (strength, flexibility
& adhesion to the tablet core).
 Hydroxy propyl methyl cellulose
(HPMC)
 Soluble in water, organic
solvent, gastrointestinal fluid
 Methyl cellulose
 Soluble in water,
gastrointestinal fluid
 Hydroxy propyl cellulose
 Soluble in Cold water,
gastrointestinal fluid
 Hydroxy ethyl cellulose
 Soluble in water,
gastrointestinal fluid
 Ethyl cellulose  Insoluble in aqueous medium
 Na- carboxy methyl cellulose  Water
2. Vinyl polymers  Poly vinyl pyrolidon (PVP)
 Soluble in water,
gastrointestinal fluid, alcohol
3. Glycols  Poly ethylene glycol (900-8000)
 Soluble in water,
gastrointestinal fluid, some
organic solvent
4. Acrylic polymers
 Methyl methacrylate
 Poly methacrylate
 copolymer amino methacrylate
 Soluble in aqueous median
with low pH

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Film coatings
Conventional film
coatings
Modified-Release
film coating
Delayed-Release
Film coatings
Extended-Release
Film coatings
Enteric film
coating

30. Ideal enteric polymer should dissolve or become permeable
near and above PH 5.0
Enteric film coating
30
Enteric coatings are those which remain intact in the stomach
and exhibit low permeability to gastric fluids. but break down
readily once the dosage form reaches the small intestine.
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31. Reasons for enteric film coating
31
 To protect & maintain the activity of drugs that are
unstable when exposed to the gastric milieu
(erythromycin and pancreatin).
 To minimize either nausea or bleeding that occurs with
those drugs that irritate the gastric mucosa (sodium
salicylate, aspirin and certain steroids).
 Deliver drugs intended for local action in the intestine.
 Provide a delayed-release component.
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32. Local action of enteric film coated tablet
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33. 33
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Polymers used in enteric film coating
Example Dissolution PH
 Natural polymers (Shellac) Soluble in PH>7
 Cellulose Acetate Phthalate
 Widely used in industry but has disadvantage of dissolving above pH 6, and
thus delays absorption.
 Latest CAP is available as Aquateric (composed of solid or semisolid
polymer spheres of CAP.
Soluble in PH>6
 Poly vinyl Acetate Phthalate (PVAP Coateric) Soluble in PH=5 – 5.5
 Hydroxy Propyl Methyl Cellulose Phthalate (HP-SS & HP-F)
Soluble in PH=5 – 5.5
 Hydroxy Propyl Methyl Cellulose Acetate Succinate Soluble in high PH
 Acrylic resins (methyl methacrylate)
Ex: Eudragit L & Eudragit S
Soluble in PH=6 – 7

34. Sustained release film coating
34
Drug release from such sustained-release products is
moderated by the film coating Which acts as a membrane
that allows infusion of GI fluids and the outward diffusion of
dissolved drug
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Objectives SR tab?

35. Polymers used in extended release coating
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Examples Commercial names
 Natural polymers
 Zein, Shellac
 Cellulosic polymers
 ethyl cellulose, vinyl cellulose …
Aquat
 Acrylic esters
 ethyl acrylate, methyl methacrylate
EudritNE 30 D

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• The function of plasticizer is to make the polymer more
pliable and soft and thereby enhancing the flexibility
and plasticity to the films.
Mechanism of action
 interpose between every individual strand of polymer and
thereby causing breakdown of polymer -polymer
interactions.
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2. Plasticizer
Role of plasticizer
 modify the physical properties of the polymers.
 reduction in tensile strength.
 decrease film brittleness.

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 increase flexibility of polymer.
 enhancing the coalescence process.
 improving the integrity of the coat.
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Continue ….
Examples of plasticizers
• Polyethylene glycol 400
• Surfactants (Tweens, Spans)
• organic acid esters (diethyl phthalate)
• water- soluble plasticizer (PEG, propylene glycol)
• organic- soluble plasticizer (castor-oil and Spans)

38. 3. Colorant
38
 Colorants may be soluble in the solvent system or
suspended as insoluble powders.
 Used to provide distinctive color and elegance to a dosage
form.
 Usually water-insoluble colors (pigments).
• chemically stable towards light
• better opacity & covering power
• Impermeable film to water vapor.
Examples of colorants:
 Iron oxide pigments.
 Titanium dioxide.
 Aluminum Lakes.
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39. 4. Solvent
39
• primarily functions as to dissolve or disperse the polymers
and other additives to the substrate surface.
Characteristics of ideal solvent
• Should dissolve or disperse the polymer system.
• Should easily disperse other coating solution components.
• Should not create the processing problems.
• Should have no color, taste, odor, inexpensive, nontoxic, inert,
and nonflammable.
• Should be easily dried.
• Should have environmental friendly.
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40. Common solvents used in film coating
Class Example
Water
Alcohols  Ethanol
 Methanol
 Isopropyl alcohol
Esters  Ethyl acetate
 Ethyl lactate
Ketones  Acetone
Chlorinated hydrocarbons  Methylene chloride
 trichlorothane
Continue …
• 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.
39

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Miscellaneous agents of coating material
 Opaquant-extenders
• talc, aluminum silicate, magnesium carbonate, calcium sulfate, Mg
oxides & titanium dioxide.
 Sweeteners
 Flavoring agents
 Surfactant
 Antioxidant
 Antimicrobials

42. Basic process requirements for film coating
42
 suitable equipment for atomizing the spray liquid for
application to the tablet cores.
 adequate mixing and agitation of the tablet bed.
 sufficient heat input in the form of drying air to Provide
the latent heat of evaporation of the solvent.
 good exhaust facilities to remove dust- and solvent-laden
air.
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Ideal characteristics of film-coated tablets
• even coverage of film and color • no abrasion of tablet edges
• Logos and break lines should be distinct and not filled in
• comply with pharmacopeial requirements

43. Examples of film coated tablets
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44. Film coating defects
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These arise from two distinct causes:
1. Problems in formulation
2. Problems in processing
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• Sticking and picking
• Roughness
• Orange –peel effects
• Bridging and filling
• Blistering
• Hazing/Dull film
• Color variation
• Cracking
• Twinning

45. 1. Sticking and picking
45
• Over wetting or excessive film thickness causes tablets to
stick to each other or to the coating pan.
• On drying at the point of contact, a piece of the film may
remain adhered to the pan or to another tablet
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Causes Remedies
• Higher rate of application of
coating solution.
• Inefficient drying
 Decrease the rater of application
of coating solution.
 Increase the inlet air temperature.

46. 2. Roughness
46
• A rough or gritty surface is a defect which is observed
when the coating is applied by spray.
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Causes Remedies
• Drying of coating solution before
reaching the surface of tablet
during spraying.
• Excessive pigments concentration.
 Moving the nozzle closer enough.
 Reducing the degree of
atomization

47. 3. Orange –peel effects
47
• This condition relates to inadequate spreading of coating
solution before drying.
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Causes Remedies
• Too rapid drying.
• High solution viscosity.
 Thinning the solution with
additional solvent.
 Use mild drying conditions.

48. 4. Bridging and filling
48
• Bridging is defect in which the bisects or monogram is
obscured / Coating shrink or pull away
• Too much of solution is applied / Filling
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Causes Remedies
• improper application of the
solution / applying too much.
• Poor logo design
• improper atomization pressure.
• high coating viscosity.
 Increase plasticizer contents or
change plasticizer concentration.
 Proper solution application..
 reduce viscosity of coating
solution.

49. 5. Blistering
49
• It is local detachment of film from the substrate.
• Entrapment of gases in or underneath the film due to
overheating.
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Causes Remedies
• Effect of temperature on the
strength, elasticity and adhesion of
the film.
 Use mild drying condition.

50. 6. Hazing / Dull film
50
• It is defect where coating becomes dull immediately or
after prolonged storage at high temperatures.
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Causes Remedies
• High temperature during
formulation.
• Exposure to high humidity
conditions.
• High concentration and low
molecular weight of plasticizer.
 Appropriate drying temperature
 Controlling humidity conditions.
 Decrease plasticizer concentration
and increase molecular weight of
plasticizer.

51. 7. Color variation
51
• A defect which involves variation in color of the film.
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Causes Remedies
• Improper mixing.
• uneven spray pattern.
• insufficient coating.
• migration of soluble dyes-
plasticizers and other additives
during drying.
 Go for geometric mixing.
 Spray uniformly.
 reformulation with different
plasticizers and additives.
 Use lake dyes.

52. 8. Cracking
52
• Cracking occurs if internal stresses in the film exceed the
tensile strength of the film.
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Causes Remedies
• internal stress exceeds the tensile
strength of the film
• Absorption of moisture.
• Excessive coating material
concentration
 Increase tensile strength of film
 higher molecular weight polymers
or polymer blends
 Minimized internal stresses of film
 Adjusting the plasticizer &
pigment type and concentration

53. Other types of film defects
53
Chipping
• This is the result of high pan speed, a friable tablet core, or
a coating solution that lacks a good plasticizer.
Twinning
Two or more tablets that sticking together
 Inefficient drying.
 Higher rate of application of coating solution
 Increasing pan speed
 Reducing spray rate
 Appropriate tablet shape
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Causes
Remedies

54. Selection of best formula
54
• primary formula (on the basis of previous experiments)
• changes in the primary formula for optimization
Evolution and development of film coating
 changes in pan designs
 Changes in film formulation
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55. 2. Sugar Coating
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• The traditional method of coating tablets.
• It involves the successive application of sucrose-based
solutions to tablet cores in suitable coating equipment.
Description of tablets: Smooth, rounded and polished to a
high gloss.
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Sugar Coating Process

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Objectives of sugar coating
• To mask unpleasant taste, odor or color.
• To protect drug from air & moisture.
• To improve appearance of tablet.
Advantages of sugar coating
• Require inexpensive and simple equipment
• Raw materials are readily available & less expensive
• The tablet produced are high quality, smooth & elegant
They have good consumer appeal.

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Coating pan
 Conventional panning equipment with manual application
of syrup has been extensively used
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Disadvantages of sugar coating
• time consuming process.
• high weight gain.
• Increase in Packaging & shipping.
• required trained personnel.
• Imprinting problems.

58. Steps involved in Sugar Coating
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1. Sealing of tablet cores (water proofing)
2. Subcoating
3. Smoothing
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6. Printing
5. Polishing
4. Colouring
3. Smoothing
2. Sub coating
1. Seal tablet core
 Application of a water impermeable polymer such as Shellac, CAP
and PVAP, which protects the core from moisture, increasing its
shelf life.
 Large quantities of sugar-coatings are usually applied to the tablet
core. by adding bulking agents such as calcium carbonate or talc in
combination with sucrose solution.
 Remove rough layers formed in
previous step with the
application of sucrose syrup
(60-70%), also Mask any defect

59. Steps involved in Sugar Coating
59
4. Coloring
5. Polishing
6.
6. Printing
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 Almost all sugar coated tab are colored.
 For aesthetic purposes & should be approved by FD&C.
• Water soluble dyes
• Water insoluble pigments
 Effectively polished to give characteristic shine, commonly using
beeswax, carnauba wax.
 Indelible ink for characterisation (manufacture name, code or logo).

60. Ideal characteristics of sugar-coated tablets
60
 comply with finished product specifications.
 should be rounded, smooth & uniform.
 sugar-coated tablets are polished & glossy.
 Any printing should be Clear and definite.
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61. Sugar coating vs. Film Coating
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Features Film Coating Sugar coating
Tablet
Tablet Appearance
Weight increase because
of coating material
Logo or ‘break lines
Retain contour of original core.
Usually not as shiny as sugar
coat.
2-3%
Possible
Rounded with high
degree of polish
30-50%
Not possible
Process
Process stages
Typical batch coating time
Functional coatings
Usually single stage
1.5-2 hrs.
Easily adaptable for controlled
release
Multistage process
8hrs. but easily
longer.
Not usually possible
apart from enteric
coating

62. Examples of sugar coated tablets
63
Brufen® POM
• Available in 200mg and 400mg
strength
Premarin® POM
• Conjugated oestrogens 625mcg
(maroon) and 1.25mcg (yellow)
Colofac ® P
• Mebeverine hydrochloride
100mg Round, white, sugar
coated
Kalms ® GSL
• 45mg Hops powder,90mg
Gentian powdered extract, and
135mg Valerian powdered
extract

63. 3. Press coating
64
 Involves the compaction of granular material around an
already preformed core using compressing equipment
similar to that used for the core itself.
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Press coating is done for following reasons:
 Used mainly to separate chemically
incompatible materials.
 Also dual release patterns possible
 Compression coating is a dry process.

64. 4. Functional Coating
65
• tablet coatings that perform a pharmaceutical function,
such as conferring controlled or enteric release on the
dosage form.
Controlled-release coatings
 Film coating provides an extremely effective way of
conferring a controlled-release aspect.
 After coating these particles are filled into hard gelatin
shells, or occasionally compressed directly into tablets.
 The coatings involved use polymers with restricted water
solubility (Ethylcellulose and modified acrylate derivatives).
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65. Multiparticulate dosage forms
66
 In multiparticulate dosage forms, the drug dose is divided
out into multiple mini-unit dosage forms, most commonly
using beads (“nonpareil” cores, 1–2 mm in diameter), which
are then loaded into a gelatin capsule.
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Types of multiparticulate
1. Extruded/spheroflized granulates
2. Non-pareils

66. Advantages over the non-disintegrating tablets
67
• Small size (typically 0.7—2.00 mm).
• Non-disintegrating tablets can be liable to lodge in the
gastrointestinal tract.
• The patient would not be exposed to any undue risk.
Mechanisms of drug release from multiparticulates
1. Diffusion
2. Erosion
3. Osmosis

67. Specialized coating: Dip coating
68
 Dip coating is a famous way of creating thin films for
research functions. uniform films may be implemented
onto flat or cylindrical substrates.
 Dipped into coating solution and then dried taking care to
prevent adherence to one another.
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68. Electrostatic dry coating
70
 This novel coating technique is an alternative to aqueous
or solvent based coating process. widely useful in:
‾ food technology
‾ paint technology
‾ metal coatings
‾ coating of tablets as well as capsules
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69. Evaluation of coated tablet
74
 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
• Enough strength to crush (Tablet hardness)
• Disintegration test
• Dissolution test
• Stability test
• Physical appearance
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Quality control of coated tablet
 Physical control
 In vitro tests
 In vivo tests

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