PRESENTATION NAME

WITH ITS DEFECTSTABLET COATING

SKB COP KAMPTEE1College name:-s.k.b college of pharmacy kamptee,nagpurAURHOR:- NILESH S.JAWALKARE-MAIL:-nilesh.jawalkar91@gmail.com

DEDICATED TO GOD OF CRICKET .SACHIN 10DULKARREASONS 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 identificationFunctional film coatings used to impart enteric or controlled-release properties

Types of tablet coating

Three main types are in use: Film coating Sugar coating Press coating 5MAJOR DIFFERENCES BETWEEN SUGER & FILM COATINGFEATURESFILM COATINGSUGAR COATINGAppearance

Retain contour of original core. Usually not as shiny as sugar coat typeRounded with high degree of polish

Weight increase because of coating material2-3%30-50%Logo or break linesPossible

Not Possible

Process stagesUsually single stageMultistage processTypical batch coating time1.5 to 2.0 HoursEight hours but easily longerFunctional coatingsEasily adaptable for controlled releaseNot usually possible apart from enteric coating6Sugar coating

multistage processIncrease bulk,mask taste,odour

1. Sealing of the tablet cores2. Subcoating3. Smoothing4. Colouring5. Polishing6. Printing.

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.Sub coating -by adding bulking agents such as calcium carbonate or talc in combination with sucrose solution. Smoothing process -remove rough layers formed in step 2 with the application of sucrose syrup.

Multistage process

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.Sub coating -by adding bulking agents such as calcium carbonate or talc in combination with sucrose solution. Smoothing process -remove rough layers formed in step 2 with the application of sucrose syrup.9

Colouring - for aesthetic purposes often titanium based pigments are included.

Polishing - effectively polished to give characteristic shine, commonly using beeswax, carnauba wax.

Printing -indelible ink for characterisation.Example of sugar coated tablets

Brufen POMAvailable in 200mg and 400mg strength

Premarin POMConjugated oestrogens 625mcg (maroon) and 1.25mcg (yellow)

Colofac PMebeverine hydrochloride 100mg Round, white, sugar coated

Kalms GSL45mg Hops powder,90mg Gentian powdered extract, and 135mg Valerian powdered extract

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;Polymer Solvent PlasticizerColourant 12Film 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.

FILM COATING POLYMERS

Ideal characteristics of a film coating polymerSolubilityFor 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.

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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.15

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.

17Mechanical propertiespolymer 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

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.

18Traditionally, the mostly commonly used polymer for the purpose of enteric coating. Is a natural and the oldest known material used for enteric coatings. Its use has been superseded by modern polymers duehttp://www.fermacol.co.uk/Shellac.htm - image searched from google shellacShellac

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: 6Additional remarks: sensitive to hydrolysis, 5-30% plasticizer required.

Polyvinyl acetate phthalate (PVAP)

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

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.

22Chemical name: Hydroxy propyl methyl cellulose phthalate (HPMC)Trade name: Application form: organic solution.Functional groups: methoxy, hydroxypropoxy, phthalyl Soluble above pH: 5Additional remarks: less sensitive to hydrolysis, plasticizer is not essentialPolymer dissolution Factors affecting the release of a drug from a polymer:

Thickness of the coating materialpHOther excipients Ionic state

24Plasticizers to modify the physical properties of the polymer to decrease film brittleness. Examples of plasticizers are:polyols, such as polyethylene glycol 400organic esters, such as diethyl phthalateoils/glycerides, such as fractionated coconut oil. only water-miscible plasticizers can be used for aqueous-based spray systems.

25Colourantswater-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.

26Solvents

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

27 Basic process requirements for film coating1. 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.

Functional coatingsFunctional coatings are coatings, which perform a pharmaceutical function. These include;

Enteric coating

Controlled release coating

28Ideal properties of enteric coating material are summarized as belowi) Resistance to gastric fluidsii) Susceptible/permeable to intestinal fluidiii) Compatibility with most coating solution components and the drug substrateiv) Formation of continuous filmv) Nontoxic, cheap and ease of applicationvi) Ability to be readily printed29Enteric coatingThis 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 pH2. To protect the stomach from the irritant effect of certain drugs3. To facilitate absorption of a drug that is preferentially absorbed distal to the stomach

30Enteric film coatingThe 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.

31Enteric 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.Examples of enteric coated OTC products Enteric coated aspirin E.g. Micropirin 75mg EC tablets

Enteric coated peppermint oil E.g. Colpermin

The ideal properties of enteric coated materialPermeable to intestinal fluidCompatibility with coating solution and drug Formation of continuous filmNontoxicCheap and ease of applicationAbility to be readily printedResistance to gastric fluids

33Ideal properties of enteric coating material are summarized as belowi)ii) iii)iv) v), vi)Resistance to gastric fluids

Permeable to intestinal fluidCompatibility with coatingsolution and drug

Formation of continuous filmNontoxic

Cheap and ease of application

Ability to be readily printed

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.

Coating equipmentscoating pans

fluid beds

fluid beds

Compression Coating Machines

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

TABLET COATING DEFECTSTablet Coating Defetcs Picking and stickingBridgingCappingErosionPeeling and frostingMottled colorChippingOrange peelTwinning

41Tablet coating :Tablet coating is defined as covering the tablets 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 color and some times flavor .Aspects of tablet coating :

Avoid irritation of stomachAvoid bad tasteAvoid inactivation of drug in the stomachImprove drug effectivenessReduce influence of moistureImprove drug stabilityImprove product identityImprove appearance and acceptability42Coating defects :An ideal coated tablet should be free from any visual defect or functional defect. But some imperfections are seen in the tablet coating for different kinds of reasons .The imperfections found in tablets coating are known as tablet coating defects .Some coating defects -TwinningColor variationOrange peelRoughnessAgglomerationChippingBlisteringBridgingCrackingPickingCappingPittingSplittingFlakingMottled colorErosionBlushing43TwinningTwo tablets stick together.Most common in capsule shaped tablets .

Cause Coating suspension can not be evaporated.

Remedy Reducing spray rateIncreasing pan speed

44Cracking Small, fine cracks observed on the upper and lower central surface of tablets, or very rarely on the sidewall are referred to as Cracks.Cause Use of higher molecular weight polymers or polymeric blendsHigher internal stresses in the film ( more than tensile strength of the film )Remedy Use low molecular weight polymerAdjust the plasticizer & pigment types and concentration to minimize internal stresses

Sticking & pickingIt is defect where isolated areas of film are pulled away from the surface when the tablet sticks together and then part. Picking does not occur alone it must have another tablet to be stuck with which called sticking .

Sticking

Picking46Sticking & pickingCause :Inefficient drying.Higher rate of application of coating solutionOver wetting Excessive film thickness

Remedy : Reduce liquid application rate. Increase in drying air temperature and air volume.

Blistering It is local detachment of film from the substrate forming a blister .

Cause :Over heating during spraying coating solution

Remedy : use mild drying condition . ChippingIt is the defect where film become chipped and dented , usually at the edges of tablet .Cause :Excessive attrition during coating process

Remedy : Increase hardness of the film .

Orange peel effects It refers to a coating texture that resembles the surface of an orange .

Cause :Rapid DryingHigh solution viscosity

Remedy :Use mild drying conditionsUse additional solvents to decrease viscosity of solution.Roughness :

The surface becomes rough and no glossy .Remedy:Reduce the degree of atomization

49Bridging Coating fills in the letter or logo on the tablet .Cause :Improper formulationPoor logo designImproper application of coating solutionImproper atomization pressureHigh percentage of solid in coating solutionHigh coating viscosityRemedy :Increase plasticizer contents or change plasticizer concentrationReduce viscosity of coating solution

Filling The monogram or bisect is filled and become narrow .

Cause :Applying too much solutionHigher solution applying rate Remedy - Control fluid application rateBlooming (Hazing/dull film)Coating becomes dull immediately or after a prolonged storage . Normally it occurs together with surface roughness.Cause - using low molecular weight plastisizer .

Remedy - increase MW & concentration of plastisizer .Erosion

Cause :Over-wetted tablet surfaceInadequate dryingLack of tablet surface strengthRemedy Control drying rate & temparature PittingIt is defect whereby pits occur in the surface of tablet coreCause Incontinuous spreading of filmtemperature of the tablet core is greater than the melting point of the materials used in tablet formulationRemedy - control drying temperatureColor variation Cause :improper mixing, uneven spray pattern, insufficient coating migration of soluble dyes , plasticizer and other additives during drying.

Remedy :Use of lake dyes eliminates dye migration. A reformulation with different plasticizer and additives is the best way to solve film instability.

Two types of color variation Individual Tablet Color variation,Whole Batch Color Variation

CrateringIt is the defect of film coating whereby volcanic-like craters appears exposing the tablet surface .Cause Penetration of the coating solution into the surface of the tablet

Remedy Decrease in spray application rate Use of optimum and efficient drying

Blushing (whitish specks) The defect best described as whitish specks or haziness of the film .It is characterized by precipitation of polymer exacerbated by the use of high coating temperature at or above the thermal gelation temperature of the polymers.AgglomerationAgglomeration caused by coating suspension cannot be evaporated as soon as it reach the tablet which may be caused from too much inlet coating suspension or too less inlet heat and the unevaporated suspension glue the tablets together. The amount of excess unevaporated suspension is much more than twinning.

Sometimes it can cause by the leaking of coating suspension into the chamber, or too close spraying distance or too low atomizing pressure.

NILESH S.JAWALKAR