Tablet coating process

This presentation is briefly explains about the steps involved in the coating process and problem arised during the process with their solutions.

1. Presented By :
Abdul Raheem.T
Industrial pharmacy
Bapuji pharmacy collage
Davangere
1

2. INTRODUCTION
Coated tablets are defined as “tablets covered
with one or more layers of mixture of various
substances such as
Natural Or Synthetic Resins
 Gums
 Inactive And Insoluble Filler,
 Sugar
 Plasticizer
 Polyhydric Alcohol
 Waxes
 Authorized Colouring Material and Flavoring agents
2

3. I.Therapy
 Avoid irritation of esophagus and stomach
 Avoid bad taste
 Avoid inactivation of drug in the stomach
 Improve drug effectiveness
 Prolong dosing interval
 Improve patient compliance
3

4. II. Technology
 Reduce influence of moisture
 Avoid dust formation
 Reduce influence of atmosphere
 Improve drug stability
 Prolong shelf life
4

5. III. Marketing
 Improve product brand identification
 Improve appearance and acceptability
Coating aids in improving sales and marketing
appeal of a drug
5

6. Tablet coating is the application of
coating composition to moving bed of
tablets with concurrent use of heated air
to facilitate evaporation of solvent.
Basic Principle of Tablet coating
6

7. Sugar coating
Film coating
Enteric coating
Controlled release coating
Specialized coating
Compressed coating
Electrostatic coating
Dip coating
Vacuum film coating
7

8. The objectives of tablet coating are as follows:
 To mask the unpleasant taste and odour of the
drug.
 To offer a physical and/or chemical protection to
the drug.
 To control and sustain the release of the drug from
the dosage form.
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9.  To minimize product damage due to physical stress
during handling.
 To protect an acid-labile drug from the gastric
environment.
 To increase the mechanical strength of the dosage
form
It helps maintaining the shape of the tablet
9

10. EQUIPMENTS FOR TABLET COATING
Three general types of equipments are available
1.Standard coating pan
e.g., Pellegrino pan system
Immersion sword system
Immersion tube system
2.Perforated pan system
e.g.,Accela cota system
Hi-coater system
Glattcoater system
Driacoated system
3.Fluidized bed coater
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11. Standard Coating Pan
Immersion-
tube system
Glatt
Immersion
sword
system
Pellegrini
pan system
STANDARD COATING PAN
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12. PERFORATED PANS
Accela cota
system
Hi-coater
system
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13. PERFORATED PANS (continue…)
Dria coater pan
Glatt coater
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14. FLUID BED COATING SYSTEMS
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15. 1.Sugar coating
2. Film coating
3. Press coating
Main coating
processes
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16. 6. Printing
5. Polishing
4. Colouring
3. Smoothing
2. Sub coating
1. Seal tablet core
Sugar coating as the name suggests is the process which
involves application of sugar (sucrose) based coating
solution for the tablets.
Process: Multistage Process involving 6 separate
operations.
Sugar coating
16

17. 1- Sealing (Waterproofing)
 Sealing is done by applying a polymer based
water impermeable coating solution by either ladling
or spray techniques.
The polymers used are natural gums like shellac,
acacia or derivatives of cellulose like cellulose
acetate pthalate (CAP), PVAP, HPMC

17

18. (WHY Sealing?)
a- Sugar-coatings are aqueous formulations which
allow water to penetrate directly into the tablet core and
thus potentially affecting product stability and possibly
causing premature tablet disintegration.
b- It enables sugar-coated product to exhibit modified-
release pattern (extended release or delayed "enteric"-
release characteristics).
c- To protect the tablet core from adverse effect of
moisture
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19. 2. Subcoating
Large quantities of sugar-coatings are usually
applied to the tablet core for increasing the tablet
weight by 50- 100%
WHY?
It is done to provide the sealed tablet cores with
round edges and to build up the core weight. It is
achieved by adding a bulking agent such as
Calcium carbonate, to the sucrose solution.
Antiadherents e.g. Talc may be added after
partial drying to prevent sticking of the tablets
together.
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20. 3- Smoothing
The sub coating stage results in tablets with rough
surfaces. To facilitate the color application (which
requires smooth surface), sub coated tablets are
smoothed out by a thick sucrose syrup coating.
4- Coloring
Color coatings usually consist of thin sucrose
syrup containing the requisite coloring materials
(water-soluble dyes or water-insoluble pigments
may be used). The colours used should be
approved by FD and C.
20

21. 5- Polishing
After the colour coating, the tablet surfaces show
a dull or matt appearance. To achieve glossy
finish, application of waxes (beeswax carnauba
wax) are employed.
6- Printing
Different tablets could be identified by
manufacturer' logo, product name, dosage strength
or other appropriate code. For sugar-coated
tablets, such identification could be only achieved
by printing process using special edible inks.
21

22. 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
EXAMPLE OF SUGAR COATED
TABLETS
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23. SUGAR COATED PROCESS
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24. Film coating involves application and deposition of a thin
film of polymer solution around the tablet core.
Process: Single stage process, which involves spraying a
coating solution containing the following;
1.Polymer
2.Solvent
3.Plasticizer
4.Colourant
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.
FILM
COATING
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25. Advantages
Produce tablets in a single step process in
relatively short period of time and suitable for
diabetic patients.
Disadvantage
They do not have elegance as that of
sugar coated tablets.
Types of film coating
A.Immediate release
B.Modified release
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26. 1.Polymer
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27. 2.Plasticizers
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 that 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.
In general, only water-miscible plasticizers can be used for aqueous-
based spray systems.

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28. 3.Colourants
Colourants are used to improve the aesthetic value of the
final product as well as helps in identifying the product.
Pigments have certain advantages over water-soluble
colours: they tend to be more chemically stable towards
light, provide better opacity and covering power.
Examples of colourants are:
• Iron oxide pigments
• Titanium dioxide
• Aluminum Lakes.
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29. 4.Solvents
 Solvents play an important role in formulation of
coating solution. They serve as a vehicle for dissolving
and dispersing the constituents of coating solutions and
helps in the applications of the coating to the tablet
surface.
 Examples for commonly used solvents are water,
alcohol ( methanol, ethanol), ketones, esters etc.
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30. 30
Film coating
Tablet appearance
Retains shape of original core
Small weight increase of 2-3%
due to coating material
Process
Can be automated e.g. Accela
Cota
Easy training operation
Single stage process
Easily adaptable for controlled
release allows for functional
coatings.
Sugar coating
Tablet appearance
Rounded with high degree of
polish
Larger weight increase 30-
50% due to coating material
Process
Difficult to automated e.g.
traditional coating pan
Considerable training
operation required
Multistage process
Not able to be used for
controlled release apart from
enteric coating.

31. Use of compression to form coat around a
pre-formed core
Used mainly to separate chemically
incompatible materials and also dual
release patterns possible
PRESS COATING
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32. Sticking and picking :
When the coating solution overwets, the tablets stick to
each other or to the coating pan. On drying , a piece of
film may remain adhered to pan or another tablet.
Solution : It can be solved by reducing the liquid
application rate or increasing the dry air temperature and
volume.
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33.  Roughness :
◦When coating is applied as a spray, some droplets may
dry before reaching the core and are deposited on the
core resulting in roughness of the surface
◦Solution : Moving the nozzle closer to the bed or
reducing the degree of atomization.
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34. Orange-Peel effect :
◦When the coating solution is sprayed inadequately or
improperly before drying causes a bumpy or “Orange-
Peel” effect on the coating.
Solution : This can be solved by thinning the solution
with additional solvent
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35. Bridging and Filling :
◦This is observed in tablets consisting of monogram
or bisection. During drying, the film may shrink
and pull away from sharp corners resulting in
Bridging of the surface depression. Filling is caused
when too much of solution is applied which fills
and narrows the monograms or bisect.
◦Solution : Bridging can be solved by increasing
the plasticizer content or changing the plasticizer
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36. Blistering :
◦When coated tablets require further drying in
ovens, too rapid evaporation of solvent from core
and the effect of high temperature may effect th
strength, elasticity and adhesion properties of the
film results in blistering. An unsmooth film surface
shows a number uneven spots called blisters.
◦Solution : It can be solved by employing milder
drying conditions.
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37.  Dull film (Bloom) :
◦This happens when high temperatures are used in
formulations. It can also happen when the coated
tablets are exposed to high humidity conditions and
also due to migration of plasticizers to the surface
of coat.
Colour Variation :
◦It is caused by processing conditions of
formulations , improper mixing, uneven spray
pattern and insufficient coating may result colour
variation
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38. Cracking :
◦Cracking occurs due to internal stresses that occur
in the film. If internal stress exceeds the tensile
strength, cracking occurs. This can be solved by
adjusting the type and concentration of plasticizer.
38

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pharmaceutics.4
th
ed. Newyork: Marcel dekker; 2005. p.318-
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rd
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pharmaceutical dosage forms and DDS: Solid dosage form
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th
ed. Pheladelphia: Lippin
cott williams and wilkins; 2005. P.247-52.
39

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Kshirsagar, Rishikesh VA. Innovations in tablet coating
technology: a review. Int J Applied Bio PharmTech 2011 Mar;
2(1): 214-8.
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