Sneha Gaurkar- Tablet Coating Industrial Pharmacy-I.ppt

Tablet Coating
Ms. S. B. Gaurkar
DRGIOP

• Tablet coating is the process of applying a thin, uniform layer of coating material
(like sugar, polymer, or enteric substances) over the surface of a tablet to protect the
drug, mask taste/odor, improve appearance, aid swallowing, and control drug
release.
Tablet coating

• Objectives of Tablet Coating:
Tablet coating
1.Mask unpleasant taste, odor, or color of the drug.
2.Improve appearance and give an attractive finish.
3.Protect the drug from environmental factors like light, moisture, and air.
4.Improve mechanical strength and reduce dusting/chipping.
5.Ease swallowing and improve patient compliance.
6.Provide identification/branding through colors, logos, or engravings.
7.Modify drug release (e.g., enteric coating, sustained release).
8.Prevent gastric irritation by delaying drug release until intestine.
In short: Protection, Appearance, Palatability, Identification, and Controlled Release.

• Types of Tablet Coating:
1. Sugar Coating
2. Film Coating
3. Gelatin Coating
4. Enteric Coating
5. Specialized Coating- a) Compression Coating (Press coating)
b) Electrostatic Spray Coating
c) Aqueous Coating
6. Modified release coating- a) Sustained/Controlled Release
b) Colon-targeted coatings (microbial degradable polymers).
Tablet coating

1. Sugar Coating: Sugar coating is a traditional tablet coating process in which
successive layers of sugar syrup (along with polymers, colorants, and opacifiers) are
applied to a tablet core to form a smooth, glossy, and attractive finish.
Tablet coating

1. Sugar Coating: Sugar-coated tablets usually have 30–50% weight increase
compared to the uncoated core.
Tablet coating
Steps (5 stages):
1.Sealing (Waterproofing): Protects core against moisture. (Materials: shellac, cellulose
acetate phthalate, Zein).
2.Sub-coating: Rounds the edges, increases tablet size. Uses gum-based syrups + dusting
powders (CaCO , talc, starch).
₃
3.Smoothing/Syruping: Multiple applications of sucrose syrup with opacifiers (TiO ).
₂
4.Color Coating: Colored syrup to provide identification.
5.Polishing: Carnauba wax, beeswax applied for glossy finish.

1. Sugar Coating:
Advantages
• Masks taste & odor of bitter drugs.
• Improves aesthetic appeal (shiny, glossy look).
• Protects drug from light, air, and moisture (if thick enough).
• Provides a smooth surface → easier swallowing.
• Helps in product identification (colors, logos).
Tablet coating

2. Film Coating: Film coating is a modern tablet coating technique in which a thin
polymer film is applied to the tablet core. The coating is usually 2–3% of the tablet
weight (much lighter than sugar coating).
Tablet coating

2. Film Coating:
Steps in Film Coating:
1.Tablet Core Preparation: Ensure smooth surface, proper hardness, and low friability (so
core can withstand coating).
2.Preparation of Coating Solution/Suspension: Dissolve/disperse film former (polymer),
plasticizer, colorant, opacifier, solvent.
3.Atomization of Coating Solution: The solution is sprayed in fine droplets onto rotating
tablets in a coating pan or perforated drum.
4.Deposition of Coating Material: Droplets spread uniformly over tablet surface, forming a
thin wet film.
5.Drying (Solvent Evaporation) : Warm air removes solvent rapidly, leaving behind a solid
polymer film.
6.Final Finishing: Ensures smooth, uniform, defect-free coating with desired color, gloss,
and strength.
Tablet coating

2. Film Coating:
Steps in Film Coating:
Advantages
Tablet coating
•Requires less coating material compared to sugar (2–3% vs 50–100%).
•Faster process → time-saving.
•Adds minimal weight to tablet.
•More durable & resistant to chipping compared to sugar coat.
•Can use functional polymers (for sustained release, enteric release, etc.).

3. Gelatin Coating: Gelatin coating involves covering compressed tablets with a thin
gelatin layer, producing tablets known as Geltabs®.
• It combines advantages of tablets and capsules.
Tablet coating
Advantages:
✔️Mask unpleasant taste/odor (gelatin is tasteless & smooth).
✔️Ease of swallowing – gelatin coat reduces roughness.
✔️Elegant appearance – shiny, capsule-like look.
✔️Tamper-resistant (harder to split than sugar/film-coated
tablets).
✔️Brand differentiation – looks unique vs plain tablets.

4. Enteric Coating: Enteric coating is a polymeric coating applied on tablets to resist
disintegration in gastric fluid (acidic pH) but dissolve in the intestine .
Thus, drug release is delayed until it reaches the small intestine.
Tablet coating
Intestine Intestine

4. Enteric Coating:
Objectives / Uses:
✔️Protect drug from gastric acid degradation (e.g., Omeprazole, Pancreatic enzymes).
✔️Prevent gastric irritation by drugs (e.g., Aspirin, NSAIDs).
✔️Targeted drug delivery to intestine for local action (e.g., Mesalamine in IBD).
✔️Improve bioavailability of acid-labile drugs.
• Weight gain due to enteric coating: usually 2–5% of tablet weight (less than sugar
coating, more than simple film coating).
• This type of tablet need not to be crushed or chewed to prevent the risk of damage due
to reaction with stomach acid.
Tablet coating

5. Compression Coating: Compression coating is a tablet-within-a-tablet technique,
where a dry coating layer of excipients/drug is compressed around a pre-formed
tablet core, instead of using a liquid coating solution.
👉 It is also called Dry Coating or Press Coating.
Tablet coating

5. Compression Coating:
Steps / Process:
1. Preparation of Core Tablet: Inner core tablet is compressed (may contain active drug
for immediate or delayed release).
2. Placement in Die Cavity: The core is placed centrally inside a die partially filled with
coating material powder.
3. Addition of Coating Material: More coating powder is added on top and sides of the
core.
4. Final Compression: Tablet is compressed again → forming an outer coating that
surrounds the inner core.
Tablet coating
•Final coated tablet is larger and heavier compared to film/sugar-coated tablets.
•Usually 50–100% weight increase due to outer coat.
•Hydrophobic coat → controls water penetration → delayed release.
•Hydrophilic coat → swells and dissolves faster → immediate release.

5. Compression Coating:
Advantages:
Tablet coating
•No solvents needed → ideal for moisture/heat-sensitive drugs.
•Can separate incompatible drugs in core & coat.
•Useful for pulsatile release
•Allows dual drug release profiles (e.g., IR + SR).
•Provides better stability for sensitive drugs compared to film/sugar coating.

Tablet coating
1. Sugar → masking & appearance.
2. Film → lightweight, durable, functional polymers.
3. Gelatin → attractive, easy swallowing, anti-counterfeit.
4. Enteric → acid-protection, site-specific release.
5. Compression → solvent-free, dual release, separates incompatibles.

• Composition for Sugar Coating:
Formulation of Tablet Coating Compositions
Stage Purpose Typical Composition
Sealing /
Waterproofing
Protects core from moisture;
improves adhesion
Shellac, Zein, CAP (polymer solution);
Plasticizers (Castor oil, PEG); Solvent
(alcohol / hydro-alcoholic)
Sub-coating
Builds bulk, rounds edges,
cushions core
Sucrose syrup; Fillers (CaCO , Talc, TiO ,
₃ ₂
Kaolin); Binders (Gelatin, Acacia, Starch
paste)
Smoothing /
Grossing
Smoothens rough surface
after sub-coating
Concentrated Sucrose syrup; sometimes
Opacifier (TiO )
₂
Color Coating
Provides color, identity,
elegance
Sucrose syrup base; Colorants (lakes, iron
oxides, soluble dyes); Opacifier (TiO )
₂
Polishing Gives glossy, shiny finish Waxes (Carnauba wax, Beeswax, Paraffin)
Printing
(Optional)
Identification/branding Edible inks (FD&C dyes, TiO , solvent base)
₂

• Composition for Sugar Coating:
•Seal coat → Shellac/Polymer + plasticizer
•Sub coat → Sucrose + fillers + gums
•Smoothing → Sucrose syrup + opacifier
•Color coat → Sucrose + colors + TiO₂
•Polish → Waxes (Carnauba/Beeswax)

• Composition for Film Coating:
Component
Aqueous Film
Coating
Non-Aqueous Film
Coating
Function
Film-forming
polymer
HPMC, HPC, PVA,
Sodium CMC,
Eudragit
HPMC, Ethyl
cellulose, CAP,
PVAP, Acrylic resins
Forms main
protective film
around tablet core
Plasticizer
PEG, Propylene
glycol, Glycerol,
Triacetin
Dibutyl phthalate,
Castor oil, Triacetin,
PEG
Increases flexibility,
reduces brittleness,
prevents cracks

• Composition for Film Coating:
Component
Aqueous Film
Coating
Non-Aqueous Film Coating Function
Colorant /
Opacifier
Titanium dioxide
(TiO ), Iron oxides,
₂
Lake colors, dyes
Titanium dioxide, Iron
oxides, Lakes, Organic dyes
Provides color, masks
core, improves
appearance &
identification
Solvent /
Vehicle
Water
Organic solvents (Alcohol,
Acetone, Methylene chloride,
Chloroform, IPA/Ethanol
blends)
Dissolves/disperses
coating materials &
allows film deposition
Additives
Talc, Surfactants
(Polysorbate 80),
Sweeteners,
Flavors
Talc, Surfactants, Lubricants,
Glidants
Prevent
sticking/tackiness,
improve processability
& tablet finish

• Composition for Gelatin Coating:
Component Examples Function
Gelatin Pharmaceutical grade gelatin
Main coating material; forms
smooth glossy film around tablet
Plasticizers
Glycerin, Sorbitol, Propylene
glycol
Provides flexibility, prevents
cracking & brittleness
Opacifiers /
Colorants
Titanium dioxide (TiO ), Iron
₂
oxides, FD&C dyes, Lake colors
Improves appearance, gives
opacity/color, masks core
Preservatives
Parabens (methyl/propyl paraben),
Sodium benzoate
Prevents microbial growth in
gelatin solution
Solvent
Purified water (sometimes with
ethanol/IPA blends)
Medium to dissolve/disperse
gelatin & other components
Additives
(optional)
Flavors, Sweeteners, Surfactants
Improves palatability, processing,
patient compliance

• Composition for Enteric Coating:
Enteric
polymers
Cellulose acetate phthalate (CAP), Hydroxypropyl
methylcellulose phthalate (HPMCP), Polyvinyl
acetate phthalate (PVAP), Methacrylic acid
copolymers (Eudragit L100, S100)
Provide acid resistance,
dissolve only at intestinal
pH
Plasticizers PEG, Dibutyl phthalate, Triacetin, Castor oil
Increase flexibility &
prevent cracks
Colorants /
Opacifiers
Titanium dioxide, Iron oxides, Lakes
Improve appearance,
brand identity, opacity
Solvent /
Vehicle
Water (aqueous enteric coating) OR organic
solvents (alcohol, acetone, methylene chloride)
Dissolve/disperse enteric
polymer
Additives Talc, Surfactants, Anti-tacking agents
Improve processing,
avoid sticking

• Composition for Compression Coating:
Core tablet
Drug + fillers + binders (same
as normal tablet formulation)
Contains active drug (can
be IR, SR, or sensitive
drug)
Outer coat (dry
granules or powder)
Fillers (lactose), Binders (PVP,
HPMC), Disintegrants (starch,
croscarmellose), Lubricants
(Mg stearate, talc), Coloring
agents
Provides protection,
modified release, or
carries second drug
Special polymers (if
required)
HPMC, Ethylcellulose, PEO,
Polymethacrylates
For controlled, delayed, or
colon-targeted release

Excipients used in Tablet Coating Compositions
Excipient Class Examples Functions
Additional
Information
Film Formers /
Coating
Polymers
HPMC, HPC, CMC-Na,
PEG, PVA, PVP, Eudragit®
(acrylic polymers), CAP,
PVAP, HPMCP, shellac
Form main coating
layer; provide
mechanical strength
& protection
Choice depends on
desired release profile
(immediate, enteric,
sustained)
Solvents
Water (aqueous), Ethanol,
Isopropanol, Methanol,
Acetone, Dichloromethane
Dissolve or disperse
coating polymers &
additives
Aqueous systems are
safer & eco-friendly;
organic solvents dry
faster but are
flammable/toxic
Plasticizers
PEG 200–600, Propylene
glycol, Glycerol, Triacetin,
Surfactants, Castor oil,
Sorbitol
Increase flexibility
& reduce brittleness
of film
Improve adhesion of
polymer to tablet core

Excipient
Class
Examples Functions
Additional
Information
Colorants
FD&C dyes, Lakes (Al-lakes),
Iron oxides (red, yellow,
black), turmeric
Provide aesthetic
appeal, product
identification, brand
recognition
Dyes are water-soluble;
lakes are insoluble and
give better opacity
Opaquant–
Extenders
Titanium dioxide, Talc,
Calcium carbonate, Kaolin
Provide opacity,
mask core color,
improve film
coverage
Titanium dioxide gives
excellent whiteness and
brightness
Flavors &
Sweeteners
Flavors: vanilla, fruit essences,
peppermint, menthol;
Sweeteners: sucrose, glucose,
sorbitol, mannitol, saccharin,
aspartame
Mask unpleasant
taste, improve
patient compliance
Mainly used in sugar-
coated & chewable
tablets

Excipient
Class
Examples Functions
Additional
Information
Surfactants /
Wetting
Agents
Polysorbates (Tween 20,
80), Sodium lauryl sulfate
(SLS), Span (sorbitan
esters), Cetyl alcohol
Aid in uniform
spreading of coating,
reduce surface tension,
improve adhesion
Ensure even
distribution of polymer
& pigments
Antioxidants
Butylated hydroxyanisole
(BHA), Butylated
hydroxytoluene (BHT),
Propyl gallate,
Tocopherols (Vit. E)
Prevent oxidative
degradation of drug,
flavors, and coating
materials
Commonly added to
polymer solutions or
flavors
Antimicrobial
Agents
(Preservatives
)
Methyl paraben, Propyl
paraben, Benzoic acid,
Sodium benzoate,
Benzalkonium chloride,
Sorbic acid
Prevent microbial
growth in aqueous
coating
solutions/suspensions
Essential for aqueous
dispersions stored
before use

Equipment employed in Tablet Coating
i) Standard Coating Pan: a) Immersion Tube system
b) Baffled pan and diffuser system
c) Immersion sword system
ii) Perforated Coating Pan: a) Accela Cota System
b) Dria Coater Pan
c) Hi-coater System
d) Glatt Coater
iii) Fluidized Bed Pan

Equipments employed in Tablet Coating
i) Standard Coating Pan:
• Also Known as “Conventional Pan System”
Design: Circular metal pan (6–80 inches / 15–200
cm diameter), tilted at ~45°.
Operation: Pan rotated horizontally by electric
motor → causes tablet tumbling.
Air Supply: Inlet port provides hot air; exhaust
duct removes moist air.
Coating Solution Application:
•Applied by spraying (atomized form) → faster,
even distribution.
•Can also be applied manually by ladling or spray
gun.
Atomization Advantage: Fine droplets → shorter
drying time, continuous coating.

i) Standard Coating Pan:
Uses: Both sugar coating & film coating.
Precautions:
•Air temperature must not degrade or decompose tablet ingredients.
Drawbacks:
•Less efficient drying
•Risk of uneven coating compared to modern perforated pans.
•Tablets may not mix properly and this may cause uneven coating
•Improper balance of inlet and exhaust air may sometimes complicate the process.
•This machine can be risky for using coating composition made in organic solvents.

a) Immersion Tube system:
•Design: Long tube immersed in tablet bed with
a spray nozzle at its tip.
•Function: Spray nozzle delivers coating
solution + hot air simultaneously.
•Air Flow: Drying air flows upward → exits
through duct system.
•Efficiency: Improved drying efficiency
compared to standard coating pan.
•Applications: Suitable for both sugar coating
and film coating.
•Advantage: Simple modification of standard
coating pan for better performance.

b) Baffled Pan & Diffuser System (Pellegrini System):
•Design: Standard coating pan fitted with baffles
+ diffuser.
•Function: Distributes drying air uniformly
across tablet bed.
•Efficiency: Improves drying efficiency
compared to plain standard pan.
•Application: Suitable only for sugar coating
(limited drying capability).
•Limitation: Not efficient enough for film
coating processes.

b) Baffled Pan & Diffuser System (Pellegrini System):

c) Immersion Sword System:
•Design: Perforated metal sword immersed in tablet
bed.
•Function: Drying air introduced through sword →
flows upward through bed.
•Efficiency: Ensures uniform drying of coated
tablets.
•Advantage: Improves drying efficiency compared
to standard pan.
•Application: Can be used for both sugar coating &
film coating.

ii) Perforated Coating Machines:
•Design: Tablet coating equipment with full or partial perforated drum.
•Operation: Drum rotates on a horizontal axis, enclosed in housing.
•Spray System: Multiple spray nozzles atomize the coating solution.
•Drying: Very efficient drying system compared to conventional pans.
•Capacity: Suitable for large-scale production (high capacity machine).
Classification:
•Side-vented pans (e.g., Accela-Cota, Hi-Coater).
•Perforated drum coaters (e.g., Driacoater, Glatt Coater).
•Advantage: Faster, uniform coating; widely used in pharmaceutical industries.

a) Accela-Cota System:
• Design: Perforated coating pan with baffles
inside rotating drum.
• Tablet Mixing: Baffles ensure free mixing of
tablets.
• Coating Application: Spray gun atomizes
coating solution → evenly directed on tablets.
• Air Flow:
• Dry inlet air enters from upper section of
drum.
• Passes through tablet bed.
• Exits via bottom perforations.
• Efficiency: Faster drying + uniform coating
→ highly efficient system.
• Use: Popular for large-scale film coating
operations.

b) Dria Coater Pan:
Design: Drum with hollow perforated ribs on inner
periphery.
Coating Application: Spray nozzle (top section)
atomizes solution onto tablets.
Air Flow:
• Drying air enters from below the tablets.
• Flows upward through tablet bed → fluidizes
tablets.
• Exits through the back of the pan.
Comparison with Accela-Cota:
Accela-Cota → air enters from top, exits bottom.
Dria Coater → air enters from bottom, exits back.
Efficiency: Ensures uniform drying + good fluidization
of tablet bed.
Use: Large-scale film coating operations.

c) Hi-Coater System:
Design:
•Coating solution + drying air directed into drum center, downward.
•Drying air exits through perforations below the drum.
•Drum inner wall partially perforated → prevents product damage.
•Outer wall fully enclosed; removable housing front for easy access.
Air Control: Rotary disc valve maintains constant exhaust air cross-section → prevents
channeling.
Working Capacity: Operates at 30–100% capacity efficiently.
Applications:
•Film coating (aqueous & solvent).
•Optional sugar coating.
•Suitable for tablets, pellets, granules & other solid products.
•Advantages: Efficient, economical, flexible, prevents product damage.

c) Hi-Coater System:

d) Glatt Coater:
Design: Similar to Accela-Cota / Fluidized bed coater.
•Drying air directed from inside the drum, passes through tablet bed, exits via exhaust duct.
•Minimizes turbulence around spray nozzle.
•Drum has unique geometry + baffles → ensures mixing + tablet protection.
•Integrated into GC Smart housing → easy access, rear-mounted suspended drum (no front
support obstruction).
Coating Application:
•Spray nozzle inside drum atomizes coating fluid.
•Provides even distribution of coating solution.
Advantages:
•High spray rates & Very short processing times.
•Effective mixing without damaging tablets.
•Produces uniform, high-quality coating.
•Consistent & accurate performance.
Use: Ideal for industrial-scale, high-efficiency film coating.

d) Glatt Coater:

iii) Fluidized Bed Coater:

Design:
•Vertical cylindrical chamber.
•Air column flows upward from bottom → causes fluidization of tablets/pellets.
•Tablets move upwards in centre, fall outwards & downwards → re-enter airflow.
•Nozzle Position: Can be top spray or bottom spray (Wurster process).
Challenges:
•Tablet cores are fragile → prone to abrasion & chipping.
•Rough surface + tablet impacts make uniform coating difficult.
Working Principle:
•Spray nozzle atomizes coating solution → deposits on tablets in fluidized state.
•Coating continues until desired thickness achieved.

Spray Systems:
1.High-Pressure Airless System
• Liquid pumped at 1.7–20 MPa (250–3000 psig).
• Orifice: 0.02–0.2 mm.
• Atomization and spray rate controlled by fluid pressure, viscosity & orifice size.
2.Low-Pressure Air Atomized System
• Liquid pumped at 35–350 kPa (5–50 psig) through larger orifice (0.05–2.5 mm).
• Low-pressure air breaks stream into fine spray.
• Controlled by fluid cap orifice, viscosity, air pressure & air cap design.
•Advantages:
•Fast drying & efficient coating.
•Suitable for tablets, pellets, granules.

Defects in Tablet Coating
1. Blistering:
Definition Cause / Reason Remedy
Local detachment of
film from the tablet
surface.
Entrapped gases due to
high drying
temperature or
overheating of core.
Use mild drying
conditions, avoid
overheating.

2. Chipping:
Film breaks away from
the edges of the tablet.
Brittle film,
insufficient plasticizer,
rough handling.
Increase plasticizer
concentration, handle
tablets gently.

3. Cratering:
Coating film pulls
away leaving volcano
like craters or exposed
core.
Overwetting, high
spray rate, improper
drying.
Reduce spray rate,
optimize drying air,
avoid overwetting.

4. Cracking / Splitting:
Film cracks across
surface or separates at
crown/edges.
High internal stress,
low elasticity, wrong
polymer–plasticizer
ratio.
Adjust polymer–
plasticizer ratio, use
flexible polymers.

5. Erosion:
Surface of tablet
wears away
during coating.
Excess coating solution,
prolonged spraying,
high attrition.
Reduce spray time, optimize
solution flow, minimize
mechanical stress.

6. Infilling (Filling):
a defect where dried coating
material, often foamy or
partially dried, accumulates
and builds up within the
recessed areas or logos on a
tablet's surface
- High viscosity of
coating suspension.
- Excess coating
material applied.
- Poor atomization of
spray.
- Reduce viscosity of
coating suspension.
- Optimize spray rate and
volume.
- Improve atomization
during coating.

7. Orange Peel / Roughness:
Rough, non-glossy
surface resembling
orange peel.
Rapid drying, high
viscosity, poor
spreading.
Use lower viscosity
solution, optimize drying,
improve atomization.

8. Picking:
Film peels away from
surface or sticks and
lifts from core.
Overwetting,
insufficient drying,
tacky surface.
Optimize drying, avoid
overwetting, adjust
spray conditions.

9. Pitting:
Small holes on tablet
surface after coating.
Core overheating →
melting/dissolution of
core.
Reduce inlet air
temperature, pre-dry
tablets.

10. Bridging:
Film closes over
debossed or engraved
marks.
Low viscosity coating
solution, excess
deposition.
Increase viscosity,
reduce excess coating,
adjust spray.

11. Color Variation:
Non-uniform color
distribution on coated
surface.
Poor mixing, migration
of soluble dyes during
drying.
Proper mixing, use
insoluble pigments,
ensure uniform drying.

12. Twinning / Doubling:
Two tablets stick
together during
coating.
Overwetting, tacky
film, low pan speed.
Increase pan speed,
reduce tackiness,
optimize spray rate.

13. Blooming:
Dull or hazy
appearance on the film
surface during storage.
Migration of
plasticizer to the
surface.
Select stable
plasticizer, store at
controlled temperature.

14. Blushing:
Whitish or hazy
appearance on the
film surface.
Inadequate polymer
coalescence, high
humidity, improper
solvent evaporation.
Optimize solvent system,
control humidity,
regulate drying.

Sneha Gaurkar- Tablet Coating Industrial Pharmacy-I.ppt

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