Tablet coating

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Presentation Transcript

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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

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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

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KEY FACTORS TABLET PROPERTIES - Shape - Tolerance - Surface area COATING PROCESS - Equipments - Parameters - Facility and ancillary equipment - Automation COATING COMPOSITION - Polymers - Solvents - Plasticizers - Colorants

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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

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CONVENTIONAL PANS Standard Coating Pan Immersion-tube system Glatt Immersion sword system Pellegrini pan system

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PERFORATED PANS Accela cota system Hi-coater system

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PERFORATED PANS (continue…) Dria coater pan Glatt coater

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SPRAY APPLICATION SYSTEMS High-pressure airless automated systems Low-pressure air automated systems

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High pressure airless system Low pressure air atomized system Difference 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 : 

Types of coating processes Three main types are used in the pharmaceutical industry today; - Film coating - Sugar coating - Compression coating

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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.

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TYPES OF FILM COATING FILM COATING Immediate release Modified release Types of film coating

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Film coating formulation (Composition of the coating liquid) 1- Polymer 2- Plasticizer 3- Colorants 4- Solvent (vehicle): Examples: water, ethanol, methanol, isopropranol, chloroform, acetone, methylethyl ketone, and methylene chloride

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Ideal characters of coating material Solubility in the coating solution Solubility required for intended use- Free water solubility, Slow water solubility, pH- dependent solubility Capacity to produce elegant looking product Stability in presence of water, heat, moisture, air, and substrate being coated and no change in properties with aging. Essentially no color, odor, or taste Compatibility with common coating solution additives Nontoxic and ease of application Resistance to cracking and should act as barrier No bridging or filling of the debossed tablet surfaces by the film former Ease of printing procedure on high-speed equipment Low cost & Ease of application without specialized equipment

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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.

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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.

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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.

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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

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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.

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Enteric Coating

Examples of enteric coated OTC products : 

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

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- Typically, tablets are sugar coated by panning technique, using traditional rotating sugar-coating pan with a supply of drying air (thermostatically controlled). - The pan is automatically rotated, allowing tablets to tumble over each other while making contact with the coating solutions which are gently poured or sprayed, portion wise onto the tablets with warm air blown to hasten drying. Each coat is applied only after the previous coat is dried.

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Simplified representation of sugar coating process

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SUGAR COATING Seal coating Sub coating Syrup coating Color coating Polishing printing

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1- Sealing (Waterproofing) This involved the application of one or more coats of a waterproofing substance in the form of alcoholic spray, such as pharmaceutical Shellac (traditionally) or synthetic polymers, 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 allow water to penetrate directly into the tablet core and thus potentially affecting product stability and possibly causing premature tablet disintegration. b- Application of many coats of partially or completely water-insoluble polymers in this step, enables sugar-coated product to exhibit modified-release pattern (extendedrelease or delayed "enteric"- release characteristics).

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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.

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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.

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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 : 

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. : 

Summary of Polymers used in pharmaceutical formulations as coating materials.

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3- Compression Compression-coating of tablets Although 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.

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Coating Problems : 

Coating Problems picking/chipping roughness sticking film cracking/peeling

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Advances in tablet coating

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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

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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

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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.

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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.

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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.

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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.

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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.

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

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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 : 

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.

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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.

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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

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REFERENCES 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

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