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Advantages Produce tablets with characteristically smooth rounded contour with even colour coverage Disadvantages Time consuming process Functional coatings are usually possible other than enteric coatings 30-50% weight increase due to coating material logo or break lines not possible .
LINKS OR DIAGRAMS OF TRADITIONAL COATING PAN AND ACCELA COTA 2) Reasons for film coating include:AppearanceTo change the color, for branding purposes or other aesthetic reasonsStabilityTo protect the active ingredient from moisture, light, and/or the acidic environment of the stomachTaste/odor MaskingTo provide an easy to swallow tablet without the bitter taste of many activesRelease characteristicsMany film coating materials have functional properties which enable the creation of sustained or delayed (enteric) release dosage forms
Tablet coating process
Presented By :
Bapuji pharmacy collage
Coated tablets are defined as “tablets covered
with one or more layers of mixture of various
substances such as
Natural Or Synthetic Resins
Inactive And Insoluble Filler,
Authorized Colouring Material and Flavoring agents
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
Reduce influence of moisture
Avoid dust formation
Reduce influence of atmosphere
Improve drug stability
Prolong shelf life
Improve product brand identification
Improve appearance and acceptability
Coating aids in improving sales and marketing
appeal of a drug
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
The objectives of tablet coating are as follows:
To mask the unpleasant taste and odour of the
To offer a physical and/or chemical protection to
To control and sustain the release of the drug from
the dosage form.
To minimize product damage due to physical stress
To protect an acid-labile drug from the gastric
To increase the mechanical strength of the dosage
It helps maintaining the shape of the tablet
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
3.Fluidized bed coater
Standard Coating Pan
STANDARD COATING PAN
PERFORATED PANS (continue…)
Dria coater pan
1. Sugar coating
2. Film coating
3. Press coating
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
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
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"-
c- To protect the tablet core from adverse effect of
Large quantities of sugar-coatings are usually
applied to the tablet core for increasing the tablet
weight by 50- 100%
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
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.
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.
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.
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.
Available in 200mg and 400mg
Conjugated oestrogens 625mcg
(maroon) and 1.25mcg
Colofac ® P
100mg Round, white, sugar
Kalms ® GSL
45mg Hops powder,90mg
Gentian powdered extract, and
135mg Valerian powdered
EXAMPLE OF SUGAR COATED
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;
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.
Produce tablets in a single step process in
relatively short period of time and suitable for
They do not have elegance as that of
sugar coated tablets.
Types of film coating
A. Immediate release
B. Modified release
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
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.
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.
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
Examples for commonly used solvents are water,
alcohol ( methanol, ethanol), ketones, esters etc.
Retains shape of original core
Small weight increase of 2-3%
due to coating material
Can be automated e.g. Accela
Easy training operation
Single stage process
Easily adaptable for controlled
release allows for functional
Rounded with high degree of
Larger weight increase 30-
50% due to coating material
Difficult to automated e.g.
traditional coating pan
Not able to be used for
controlled release apart from
Use of compression to form coat around a
Used mainly to separate chemically
incompatible materials and also dual
release patterns possible
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
◦ 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.
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
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
◦ 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
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
Colour Variation :
◦ It is caused by processing conditions of
formulations , improper mixing, uneven spray
pattern and insufficient coating may result colour
◦ 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.
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