tablet coating

1. welcome

2. TABLET COATING
Anju K John
mpharm

3. DEFINITION
Tablet coating is the application of a
coating material to the exterior of a tablet
with the intention of conferring benefits
and properties to the dosage form over the
uncoated variety.
Also applicable to modified release dosage
forms &also to hard-shell and soft elastic
capsules (less extent)

4. REASONS FOR COATING TABLETS
• protection particularly from light and
moisture.
• Mechanical strength,reduse cross
condamination, dusting
prevented, mask tastes,easier to
swallow
• Coloured coating rapid
identification, patient compliance, in
marketing brand identification
• Functional film coatings used to impart
enteric or controlled-release properties

5. Types of tablet coating
Three main types are in use:
• Film coating
• Sugar coating
• Press coating

6. Sugar coating
• multistage process
• Increase bulk,mask taste,odour
1. Sealing of the tablet cores
2. Subcoating
1. Seal tablet core
3. Smoothing 2. Sub coating
3. Smoothing
4. Colouring
4. Colouring 5. Polishing
6. Printing
5. Polishing
6. Printing.

7. Multistage process
1. Sealing tablet core- application of a water
impermeable polymer such as
Shellac, cellulose acetate phthalate and
polyvinyl acetate phthalate, which protects
the core from moisture, increasing its shelf
life.
2. Sub coating -by adding bulking agents such
as calcium carbonate or talc in combination
with sucrose solution.
3. Smoothing process -remove rough layers
formed in step 2 with the application of
sucrose syrup.

8. 4. Colouring - for aesthetic purposes often
titanium based pigments are included.
5. Polishing - effectively polished to give
characteristic shine, commonly using
beeswax, carnauba wax.
6. Printing -indelible ink for characterisation.

9. Example of sugar coated tablets
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

10. Film coating
• 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
containing the following;
1.Polymer
2.Solvent
3.Plasticizer

11. Film coating
Advantages
single step process in relatively short period of
time. Process enables functional coatings to be
incorporated into the dosage form.
Disadvantages
There are environmental and safety
implications of using organic solvents as well
as their financial expense.

12. FILM COATING POLYMERS
Ideal characteristics of a film 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.

13. 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.

14. 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.

15. Mechanical properties
polymer must be
• one with adequate strength to
withstand the impact and abrasion
encountered in normal handling.
(development of cracks )
• comply with the relevant regulatory
and pharmacopoeial requirements

16. Shellac
• Material of natural origin- purified resinous
secretion of the insect Laccifer lacca.
• Oldest known material used for enteric
coatings.
• Suited for drug targeting in the distal small
intestine as soluble at pH 7.0
• Its use is now less popular in commercial
pharmaceutical applications for enteric
coatings. Due to poor batch to batch
reproducibility, which is a crucial requirement.

17. Shellac

18. Cellulose acetate phthalate (CAP)
Chemical name: Cellulose acetate phthalate
Trade name: CAP, Aquateric
Application form: organic or aqueous
dispersion
Functional groups: acetyl, phthalyl
Soluble above pH: 6
Additional remarks: sensitive to
hydrolysis, 5-30% plasticizer required.

19. Polyvinyl acetate phthalate (PVAP)
• Chemical name: polyvinyl acetate phthalate
• Trade name: Opadry enteric (aqueous),
Coloron
• Application form: organic solution, aqueous
dispersion.
• Functional groups: acetyl, phthalate,
vinylacetat :crotonic acid ratio 90:10.
• Soluble above pH: 5
• Additional remarks: Plasticizer is required.

20. Acrylic polymers
• Chemical name: Methacrylic
• Trade name: Eudragit®
• Application form: organic solution or
aqueous dispersion.
• Functional groups: methyacrylic acid
• Soluble above pH: 5 * depends on co-
polymers used.

21. Polymer dissolution
Factors affecting the release of a drug from a
polymer:
• Thickness of the coating material
• pH
• Other excipients
• Ionic state

22. Plasticizers
 to modify the physical properties of the
polymer
 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.
 only water-miscible plasticizers can be used
for aqueous-based spray systems.

23. Colourants
water-insoluble colours (pigments).
Pigments have certain advantages over water-
soluble colours: 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 colourants are:
iron oxide pigments
 titanium dioxide
 aluminium Lakes.

24. Solvents
• water is used as polymer solvent
• The disadvantages of organic solvents for the
process:
organic solvent vapor into the atmosphere is
ecologically unacceptable, and efficient solvent
vapor removal from gaseous effluent is
expensive.
Explosive ,so safety prblem

25. Basic process requirements for
film coating
1. adequate means of atomizing the spray
liquid for application to the tablet cores.
2. adequate mixing and agitation of the
tablet bed.
3. sufficient heat input in the form of
drying air to Provide the latent heat of
evaporation of the solvent.
4-good exhaust facilities to remove dust-
and solvent-laden air.

26. Functional coatings
Functional coatings are
coatings, which perform a
pharmaceutical function.
These include;
Enteric coating
Controlled release coating

27. Enteric coating
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:
1. Prevention of acid attack on active
constituents unstable at low pH
2. To protect the stomach from the irritant
effect of certain drugs
3. To facilitate absorption of a drug that is
preferentially absorbed distal to the
stomach

28. Enteric film coating
The enteric polymers (CAP,PVAP, suitable
acrylic derivative ) are capable of forming a
direct film in a film-coating process.
Sufficient weight of enteric polymer must be
used to ensure an efficient enteric effect.
This is normally two or three times that
required for a simple film coating.

29. Enteric sugar coating
The sealing coat is modified to comprise one of
the enteric polymers in sufficient quantity to
pass the enteric test for disintegration. The
subcoating and subsequent coating steps are
then as for conventional sugar coating.

30. Examples of enteric coated OTC
products
• Enteric coated aspirin E.g.
Micropirin® 75mg EC tablets
• Enteric coated peppermint
oil E.g. Colpermin®

31. The ideal properties of enteric
coated material
Permeable to intestinal fluid
Compatibility with coating solution and
drug
Formation of continuous film
Nontoxic
Cheap and ease of application
Ability to be readily printed
Resistance to gastric fluids

32. Controlled-release coatings
 After film coating these particles are filled
into hard gelatin shells, or occasionally
compressed directly into tablets by a
process which permits minimal rupture of
the applied film.
 The coatings involved use polymers with
restricted water solubility or
permeability, and include ethylcellulose and
modified acrylate derivatives.

33. Polymers used in pharmaceutical
formulations as coating materials.
Polymer Trade name Application
Shellac EmCoat 120 N  Enteric Coatings
Marcoat 125  Taste/Odor Masking
Cellulose acetate Aquacoat CPD®  Enteric Coatings
Sepifilm™ LP  Taste masking
Klucel®  Sustained release coating
Aquacoat® ECD  Sub coat moisture and barrier
Metolose® sealant pellet coating
Polyvinylacetate phthalate Sureteric®  Enteric Coatings
Methacrylate Eudragit®  Enteric Coatings
 Sustained Release
 Taste Masking
 Moisture protection
 Rapidly disintegrating Films

34. Press coating
process involves compaction of coating material
around a preformed core. The technique differs
from sugar and film coating process.
Advantages:This process enables incompatible
materials to be formulated together, such that
one chemical or more is placed in the core and
the other (s) in the coating material.
Disadvantages :Formulation and processing of
the coating layer requires some care and relative
complexities of the mechanism used in the
compressing equipment.

35. Coating equipments
• coating pans

36. • fluid beds

37. Compression Coating Machines

38. Accela-Cota: It is a prototype of perforated
cylindrical drum providing high drying air
capacity. Therefore it is preferred for film
coating.

39. Hi-coater system: The drying air is directed
into the drum is passed through the tablet
bed, and is exhausted through the
perforations in the drum.

40. Tablet coating problems
• Picking and sticking
•Bridging
•Capping
•Erosion
•Peeling and frosting
•Mottled color
•Chipping
•Orange peel
•Twinning

41. Picking and sticking: This is when the
coating removes a piece of the tablet from
the core.
• Caused by over-wetting the tablets, by
under-drying, or by poor tablet quality.
Bridging: This occurs when the coating fills
in the lettering or logo on the tablet.
– improper application of the solution,
– poor design of the tablet embossing,

42. Capping: This is when the tablet separates in
laminar fashion.
• The problem stems from
– improper tablet compression
– over-dry the tablets in the preheating
stage. That can make the tablets brittle
and promote capping.
Erosion: This can be the result of soft
tablets, an over-wetted tablet
surface, Inadequate drying or lack of tablet
surface strength.

43. Peeling and frosting: This is a defect where
the coating peels away from the tablet
surface in a sheet.
• This could be due to a defect in the ,
– coating solution,
– over-wetting or
– high moisture content in the tablet core
Chipping: This is the result of high pan
speed, a friable tablet core, or a coating
solution that lacks a good plasticizer.

44. Mottled color: This can happen when the ,
– coating solution is improperly prepared
– the actual spray rate differs from the target
rate
Orange peel: This refers to a coating texture
that resembles the surface of an orange.
• It is usually the result of high atomization
pressure in combination with spray rates
that are too high.
• By thinning the solution prevented

45. Twinning: This is the term for two tablets that
stick together, and it’s a common problem
with capsule shaped tablets.
– We can solve this problem by balancing
the pan speed and spray rate.
– Try reducing the spray rate or increasing
the pan speed.

46. REFERENCE
• Pharmaceutical dosage forms: Tablets
volume III,edited by A.Lieberman,Leon
Lachman,and Joseph B.Schwartz.
• Dispensing for pharmaceutical students by
Cooper and Gunn’s.