ST.PETERS INSTITUTE OF PHARMACEUTICAL SCIENCES VIDHYANAGAR ,HANMAKONDA

WARANGAL.

PRESENTED BY

B.MAHALAKSHMI

M.PHARMACY, IstSEMISTER

PHARMACEUTICS

HISTORICAL PERSPECTIVEINTRODUCTIONKEY FACTORSTYPES OF TABLET COATING

- FILMCOATING - SUGAR COATING

TABLET DEFECTSADVANCES IN TABLET COATINGCONCLUSIONREFERENCES

CONTENTS

HISTORICAL PERSPECTIVE

Based on Islamic literature (850-923) “Rhazes”

Sugar coating (1800, 1837-1840) for Cubeb and Copaiba

Dr. “Dale wurster”(1950)-Air suspension coater

Abbott laboratories (1953)

Accela cota, Hi-coater, Dria coater

WHAT IS TABLET

COATING?

WHY COAT TABLETS?

INTRODUCTION

4.To Mask Color,

Odour, Taste of the drug

3.Stability

5.Control the release

6.Protection from

GI fluids

DEFINITION

Of coating

1.Identification

2.Improve

elegance

KEY FACTORS

TABLET PROPERTIES - Shape - Tolerance - Surface area

COATING PROCESS - Equipments - Parameters - Facility and ancillary equipment - Automation

COATING COMPOSITION - Polymers - Solvents - Plasticizers - Colorants

Conventional Pan Systems

Perforated Pans Systems

Fluid Bed Systems

COATING PROCESS

Equipments Parameters

Air Capacity

Coating Composition

Tablet Surface Area

Equipment efficiency

Spray application systems

High-pressure air automated systems

Low pressure air automated systems

CONVENTIONAL PANS

Standard Coating Pan

Immersion-tube system

Glatt Immersion

sword system

Pellegrini pan system

PERFORATED PANS

Accela cota system

Hi-coater system

PERFORATED PANS (continue…)

Dria coater pan

Glatt coater

FLUID BED COATING SYSTEMS

SPRAY APPLICATION SYSTEMS

High-pressure airless automated systems

Low-pressure air automated systems

• High pressure airless system• Low pressure air atomized systemDifference in the system is atomization of liquid.• Airless system - Liquid pumped at high pressure (250-3000 psig) through

small orifice, fine spray.Degree of atomization depends on

- Fluid pressure- Orifice size- Viscosity of liquid

• Air atomized - Liquid pumped through large orifice at low pressure (5-50 psig). Air contacts liquid stream at tip of atomizer and fine spray is produced.

Controlling variables- Fluid pressure- Fluid cap orifice- Viscosity of liquid- Air pressure- Air cap design

Choice depends on coating solution composition for a particular product.

TYPES OF COATING PROCESSES

• Three main types are used in the pharmaceutical industry today;

• - Film coating

• - Sugar coating

• - Compression coating

• 1- FILM COATING (the most popular today)

• It involves the deposition, usually by spraying method, of a thin uniform film of a polymer formulation surrounding a tablet.

TYPES OF FILM COATING

FILM COATING

• Immediate release

• Modified release

Types of film coating

Film coating formulation (Composition of the coating liquid)1- Polymer2- Plasticizer3- Colorants4- Solvent (vehicle): Examples: water, ethanol, methanol, isopropranol, chloroform, acetone, methylethyl ketone, and methylene chloride

Ideal characters of coating materialSolubility in the coating solutionSolubility required for intended use- Free water solubility, Slow

water solubility, pH- dependent solubilityCapacity to produce elegant looking productStability in presence of water, heat, moisture, air, and substrate

being coated and no change in properties with aging.Essentially no color, odor, or tasteCompatibility with common coating solution additivesNontoxic and ease of applicationResistance to cracking and should act as barrierNo bridging or filling of the debossed tablet surfaces by the film

formerEase of printing procedure on high-speed equipmentLow cost & Ease of application without specialized equipment

PLASTICIZERS

• Internal plasticizers: Chemical modification of the polymer that alters the physical properties.

– Degree of substitution

– Type of substitution

– Chain length.

• External plasticizers : They are non-volatile or the other polymer, which when include with primary polymeric film former, changes the

– Flexibility

– Tensile strength, or

– Adhesion properties of the resulting film.

Concentration Of Plasticizer Expressed As

- The amount of polymer being plasticized.

• Recommended Level of Plasticizer : 1 to 50% by weight of the film former.

EXAMPLES

• Castor oil; propylene glycol of 200 and 400 series; and surfactants eg; Tweens; Spans; and organic acid esters.

• Water- soluble plasticizer : PEG, propylene glycol.

• Organic- soluble plasticizer : castor-oil and Spans.

COLORANTS

• Colorants may be soluble in the solvent system or suspended as insoluble powders.

• Used to provide distinctive color and elegance to a dosage form.

• To achieve proper distribution of suspended colorants in the coating solutions requires the use of fine-powdered colorants (< 10 microns ).

• Most of colorants are synthetic DYES or LAKES OF DYES approved by the FD&C and D&C.

LAKES : derived from dyes by precipitating with carriers. Eg ; alumina or talc.

• Lakes contains 10 to 30 % of the pure dye content.

• For very light shade, concentration : less than 0.01 %. • For dark shade, concentration : more than 2.0 %

• Examples– Inorganic materials: iron oxides– Natural coloring materials :Anthocyanins, caramel, carotenoids,

chlorophyll, indigo, flavones, turmeric, and carminic acid.

• Various concentrates promoted as achieving less lot-to-lot color variation

• Opalux – Opaquant color concentrate for sugar coating.• Opaspray- Opaque color concentrate for film coating. • Opadry – Complete film coating concentrate

OPAQUANT-EXTENDERS

• These are very fine inorganic powders used in the coating

solution formulation to provide more pastel colors and

increase film coverage.

• Opaquant provides a white coating or mask the color of the

tablet core, and thus the less amount of the colorants are

required.

• Examples: Silicates (talc, aluminium silicate); Carbonates

(magnesium carbonate); Sulfates (calcium sulfate); Oxides

(Mg oxides)

ENTERIC COATING

The technique involved in enteric coating is protection of the tablet core from

disintegration in the acidic environment of the stomach by employing pH

sensitive polymer, which swell or solubilize in response to an increase in pH to

release the drug.

Aims of Enteric protection: To mask taste or odour Protection of active ingredients, from the acidic environment of the stomach. Protection from local irritation of the stomach mucosa. Release of active ingredient in specific target area within gastrointestinal tract.

Enteric Coating

Examples of enteric coated OTC products

• Enteric coated aspirin E.g. Micropirin® 75mg EC tablets

• Enteric coated peppermint oil E.g. Colpermin®

- Typically, tablets are sugar coated by panningtechnique, using traditional rotating sugar-coatingpan with a supply of drying air (thermostaticallycontrolled).

- The pan is automatically rotated, allowing tablets totumble over each other while making contact with thecoating solutions which are gently poured or sprayed,portion wise onto the tablets with warm air blown to hastendrying. Each coat is applied only after the previous coat isdried.

Simplified representation of sugar coating process

SUGAR COATING

• Seal coating • Sub coating • Syrup coating• Color coating• Polishing • printing

1- Sealing (Waterproofing)This involved the application of one or more coats of awaterproofing substance in the form of alcoholic spray, such as pharmaceutical Shellac (traditionally) or syntheticpolymers, such as CAP.( Unless a modified-release feature needs to be introduced, the amount of the sealing coat applied should be carefully calculated so that there is no negative effect on the drug release characteristics in case of immediate release product.) (WHY Sealing?)a- Sugar-coatings are aqueous formulations which allowwater to penetrate directly into the tablet core and thuspotentially affecting product stability and possibly causingpremature tablet disintegration.b- Application of many coats of partially or completelywater-insoluble polymers in this step, enables sugar-coatedproduct to exhibit modified-release pattern (extendedreleaseor delayed "enteric"- release characteristics).

• 2. Subcoating

• - Large quantities of sugar-coatings are usually applied to the tablet core (typically increasing the tablet weight by( 50- 100%)

• WHY?

• In order to round off the tablet edge. Much of this material build-up occurs during this stage and 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.

• 3- Smoothing

• The subcoating stage results in tablets with rough surfaces. To facilitate the color application (which requires smooth surface), subcoated 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) This step must be done into a clean pan deprived of any residues from the previous operations.

• 5- Polishing

• After the coloring step, the tablet surfaces tend to be smooth but somewhat dull in appearance. To achieve glossy finish, final stage involving application of waxes (beeswax carnuba wax) is 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.

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

Summary of Polymers used in pharmaceutical formulations as coating

materials.Polymer Trade name Application

Shellac EmCoat 120 N

Marcoat 125

Enteric Coatings Taste/Odor Masking

Cellulose acetate Aquacoat CPD® 

Sepifilm™ LP

Klucel®

Aquacoat® ECD

Metolose®

Enteric Coatings Taste masking Sustained release coating Sub coat moisture and barrier sealant pellet coating

Polyvinylacetate phthalate Sureteric® Enteric Coatings

Methacrylate Eudragit®  Enteric Coatings Sustained Release Coatings Taste Masking Moisture protection Rapidly disintegrating Films

3- Compression Compression-coating of tabletsAlthough less popular, it gained increased interest in recent years for creating modified-released products involves the compaction of granular materials around preformed tablet core using specially designed tableting equipment. Compression coating is a dry process.

TABLET DEFECTS

STICKING AND PICKING

ROUGHNESS

ORANGE PEEL EFFECTS

BRIDGING AND FILLING

BLISTERING

HAZING/DULL FILM

COLOR VARIATION

CRACKING

Coating Problems

• picking/chipping

• roughness

• sticking

• film cracking/peeling

• BRIDGING & FILLING

• ORANGE PEEL EFFECT

Advances in tablet coatingAdvances in tablet coating

SPECIALIZED COATING TECHNIQUICS

• In this, cores to be coated are a held in a suitable device eg: baskets

• Dipped into coating solution and then dried taking care to prevent

adherence to one another.

• For obtaining more perfect or heavier coats the dipping and drying

steps may be repeated several times one after another.

• Several dipping arrangements are obtainable, amongst them the

sophisticated devices comprise tiny suction tubes, which hold the

individual tablets apart until drying is accomplished.

• Before proceeding to coat additional tablets or begin recoating cycles.

DIP-COATING

SPECIALIZED TECHNIQUICS (continue…)

• Electrostatic coating is employed for applying films of electro-

conductive materials.

• In this, an ionic charge is imparted to the core and an opposite charge

to the coating material. This technology ensures thin, continuous and

electronically perfected film to the surface.

ELECTROSTATIC-COATING

SPECIALIZED TECHNIQUICS (continue…)

LAMINATED-COATING

Laminated coating provides multiple layers for incorporation of

medicament; for example

• Repeat-action tablet, here a portion of the drug is kept in outer lamella

or coating

• Enteric tablet, here one drug could be made available for gastric

absorption while another for release in intestine

• Buccal-swallow tablet, this could first be administered sublingually,

and upon a signal, such as release of flavour from the inner core, the

same may be swallowed as a normal peroral tablet.

SPECIALIZED TECHNIQUICS (continue…)

VACCUM FILM-COATING

This employs a specially designed baffled pan, which is water-jacketed

and could be sealed to achieve vacuum.

Tablets are placed in the sealed pan, the vacuum is applied and the

coating material is introduced through airless hydraulic spray system.

Since the pan is completely sealed.

Organic solvents could be effectively used with minimal

environmental or safety concern.

ADVANCED TECHNIQUICS

SUPERCELL-COATING

Supercell coating technology is an invention of Niro Pharma,

which uses a small modular design where tablets are coated in

batches ranging from 30 to 40 grams, and which is amenable to

linearly scale up to the production capacities.

In this, typically tablets are coated with coating spray in the

same direction as the drying gas, hence, resulting in a more

efficient process.

ADVANCED TECHNIQUICS

SUPERCELL-COATING (continue…)

• Dry coating avoids the use of water or, at least, allows it to be reduced to very small amounts with respect to the coating material, thus overcoming the need for time- and energy-consuming drying phases, as well as possible drug stability issues.

• In this technology, powdered coating materials are directly coated onto solid dosage forms without using any solvent, and then heated and cured to form a coat.

DRYCOATING

• Plasticizer-dry-coating

• Electrostatic-dry-coating

• Heat-dry-coating

• Plasticizer-electrostatic-heat-dry-coating

CURRENT DRY COATING TECHNOLOGIES

PLASTICIZER DRY COATING

Film formation in the plasticizer-dry-coating

The film formation is the combined response of improved viscous flow and particle deformation resulted from plasticizer and heat. Applications - Both tablets and pellets can be coated.

Limitations

- Coat thickness increases with increasing plasticizer concentration.- However,surplus plasticizer leads to very soft or sticky films.

ELECTROSTATIC-DRY-COATING

Schematic diagram of: (a) an electrostatic coating apparatus for solid dosage forms. (10) tablet feeding chute; (12, 12) rotary drum; (16, 16) electrostatic spraying gun; (18, 18) tray to hold particles; (20, 20) infrared ray heater; (22) tablet collection chute; (A) preconditioning station; (B) coating station; (C) fusing station.

Applications

• This special design aims at making every tablet effectively grounded, and directing and restricting the charged particles onto the tablet surface without spraying onto the surrounding, by which the coating efficiency is greatly improved.

• Moreover, the two sides of a tablet may be coated with different color or different formulation.

Drawbacks

• This apparatus was found unable to focus all charged powder to the tablets but the drum also received some powder. This is wasteful of powder and also makes cleaning of the apparatus time consuming.

(1) rotating disk; (2) infrared lamp; (3) powder feeder; (4) temperature probe; (5) coating tablets; (6) glass cover

Heat-Dry-Coating

• The advantages of heat-dry-coating include abandoning plasticizer for lower Tg film-forming polymers or avoiding high concentrations of plasticizer because of pre-plasticization.

• However, it is still a challenge for heat-dry-coating technology to get a smooth, uniform and thick coating only by the help of heat-based adhesion.

PLASTICIZER-ELECTROSTATIC-HEAT-DRY-COATING

Coating process comprises the steps

• Positioning pre-heated solid dosage forms in a chamber of a rotatable, electrically grounded pan coater

• Spraying powdered coating materials and plasticizer on the solid dosage forms in the pan coater during rotation there of for a pre-selected length of time using an electrostatic spray gun

• Curing the coated solid dosage forms to form continuous, uniform and flexile coats.

It is an integration of five kinds of “forces”:

- Softening or melting effects

- Wetting

- Electrostatic attraction forces

- Hydrodynamic force

- Mechanical force.

• These are combined to enhance the adhesion of powdered coating materials to solid dosage surface.

Applications

• Conventional coating pharmaceutical polymers,such as Eudragit RS, Eudragit RL, Eudragit L, Eudragit EPO in combination with standard excipients were successfully coated onto tablets and beads.

• Produce smooth and uniform coating surfaces with controlled coating thickness on both larger dosage forms and smaller ones.

Limitations

Particularly applicable for pharmaceutical coating only with

a single colour.

CONCLUSIONCONCLUSION

ADVANTAGES OF TABLET COATING

Enhance palatability, mask unpleasant taste, odour and color of the

API

Increase the stability

Increase the mechanical integrity

Enhance the elegance

Protect the patient

Modify the drug release profile

Avoid the side effects

REFERENCES

www.pubmed.comwww.wikipedia.com

www.google.com

websites

The science and Practice of Pharmacy, Remington Volume 1

The Theory and Practice of Industrial Pharmacy by A. Lachman, 3rd Edition

Pharmaceutical Dosage forms by Liberman, Volume 3

THANK YOU

FOR

YOUR ATTENTION