#Contents# #DEFINITION #OBJECTIVES OF TABLET COATING #TABLET PROPERTIES #EQUIPMENTS #TYPES OF COATING #FILM DEFECTS #CONCLUSION

1. A Presentation on
TABLET COATING
Goverment College of Pharmacy , Amravati. 444604.
2017-2018
Presented By
Sarang Vilas Dalvi

2. Contents :
• DEFINITION
• OBJECTIVES OF TABLET COATING
• TABLET PROPERTIES
• EQUIPMENTS
• TYPES OF COATING
• FILM DEFECTS
• CONCLUSION

3. TABLET COATING
 Tablet coating is the last critical step in the tablet production
cycle.
 It is the phenomenon of application of coating to the tablet.

4. OBJECTIVES OF TABLET COATING
 To mask the taste, odor, color of the drug.
 To provide physical and chemical protection for the drug.
 To protect the drug from the gastric environment of stomach
with an acid resistant enteric coating.
 To improve pharmaceutical elegance by the use of special
colors and contrasting printing.
 To prevent GI irritation and GI instability.

5. TABLET PROPERTIES
In coating process the tablet roll in coating pan in air stream of an air
suspension coater as coatins composition is applied. To tolerate the
intense attrition of tablet striking other tablets or walls of coating
equipment, the tablet must be resistant to abrasion and chipping.
The ideal tablet shape for coating is sphere, which allows tablets to roll
freely in coating pan, with minimal tablet to tablet contact.
The worst shape is square flat faced tablet, in which case coating
material would collect between the the surfaces to glue them together.

6. EQUIPMENTS
• The equipments used for the tablet coating are :-
a) Conventional coating pan.
b) Perforated pan.
c) Fluidized bed coater.

7. A) Conventional coating pan:
The pan is 8 to 60 inches in diameter and is rotated on its
horizontal axis by a motor.
Heated air is directed into the pan and onto the tablet bed
surface, is exhausted by means of ducts.
Coating solutions are applied to the tablets by ladling or
spraying the material onto rotating tablet bed.

8.  To improve the drying efficacy of coating pans the
modifications developed such as
1. Pelligrini (system) pan
2. Immersion sword system
3. Immersion tube system
1. Pelligrini (system) pan:
• Baffled pan
• Diffuser(distributes the drying air uniformly over the tablet
• bed surface).

9. Fig 1: Standard Coating Pan

10. 2. 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.
3. 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.

11. Fig 2: Immersion sword system Fig 3: Immersion tube system

12. B) Perforated pan.
It consists of perforated drum that is rotated on its
horizontal axis.
Coating material is spray through nozzles which are
placed within pan.
Perforated pan coaters are:
1.Accela coater
2.Hi coater
3.Dria coater

13. 1.Accela coater & 2. Hi coater
• Drying air is directed in to the drum,
• Passed through tablet bed,
• Exhausted through perforations in drum.
Accela coater Hi coater

14. 3.Dria coater
• 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.
Dria coater

15. C) Fluidized bed coater.
Highly efficient drying systems
The airflow is controlled so that more air enters the centre
column, causing the tablets to rise in the centre.
The movement of the tablets is upward through the centre
of the chamber.
They then fall toward the chamber wall and move
downward to re enter the air stream at the bottom of the
chamber.

16. Coating solutions are continuously applied from a spray
nozzle located in the upper region of chamber.
There are two types of systems to apply a finely divided
spray of coating solution or suspensions onto tablets
a) High pressure, airless
b) Low pressure, air atomized

17. Airless spray system
• Liquid is pumped at high pressure (250-3000 pounds per square
inch gauge)
• through a small orifice (.009 inch to .020inch) in the fluid
nozzle Which results in a finely divided spray.
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)

18. Fig: Fluidized bed coater

19. TYPES OF COATING
A) Sugar coating
• It involves the application of sugar solution,The basic sugar
coating process involves following steps :
a)Sealing
b)Subcoating
c)Syruping
d)Polishing

20. a) Sealing
• It is applied to prevent the moisture penetration into tablet core.
• Materials used are - shellac, zein, Oleic acid, alcohol,methylene
chloride.
• Zein is alcohol-soluble protein derivative.
b)Subcoating
• It is applied to round the edges and build up the tablet size.
• Sub coating increases the tablet weight from 50 to 100 percent.
• Materials used are - Gelatin, sugarcane powder, corn syrup,
starch , distilled water, Gum acacia

21. c)Syruping
• This step is to cover and fill in the imperfections in the tablet
surface caused by the sub coating step and to impart the desired
color to tablet.
• The first syrup coats usually contain some suspended powders
and are called “Grossing syrups”.Dilute colorants can be added
to this phase.
• In subsequent syruping steps, syrup solutions containing the
dye are applied until the final size and color achieved.

22. d)Polishing
• The desired luster to the tablet is obtained by polishing.
• Materials used are - carnauba wax, bees wax,paraffin wax.
fig: sugar coating

23. B)Film coating
• It is a process that involves the deposition of a thin, but uniform
film on to the surface of the substrate.
• These tablets are far more resistant to destruction by abrasion
than are sugarcoated tablets.
• Materials used in film coating are:
 Polymers (non enteric and enteric)
 Solvents
 Plasticizers
 Colorants

24. A)Polymers in non-enteric coating:
They are incorporated to give uniform film with desired
mechanical strength which are as follows
1.Hydroxypropryl Methylcellulose (HPMC) USP
• Polymer is prepared by reacting alkali-treated cellulose first
with methyl chloride and then with propylene oxide.
• The resulting products are commercially available in different
viscosity grades.
• it has to be mixed with other polymers or plasticizers.

25. 2. Ethyl cellulose NF
• It is manufactured by the reaction of ethyl chloride with
cellulose dissolved in NaOH.
• It is water insoluble & thus Cannot be used alone for tablet
coating
• It is usually combined with HPMC to prepare film with reduced
water soluble Properties.
3. Sodium carboxymethylcellulose USP
• Its available in low, medium, high and extra high viscosity
grades. Its sodium salt of carboxymethylcellulose.

26. B)Polymers in enteric coating:
1.Cellulose acetate phthalate (CAP)
• It is widely used.
• It is hygroscopic and relatively permeable to moisture and
gastric fluids in comparison with some other enteric polymers.
2.Acrylate
• Two forms of commercially available enteric acrylic resins are
Eudragit L & 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.

27. FILM DEFECTS

28. CONCLUSION
Coating is one of the important technique in
manufacturing of dosage forms, improve the stability,
shelf life and release pattern .
Coating of dosage forms helps in improving patient
compliance.
Now-a-days, advanced techniques are preferred over the
conventional types, because of effective coating, taking
less time, and also improve the stability of the product
(chances of degradation in coating time).