Type of Defect

8/8/2019 Type of Defect

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Tablet:Problems in tablet manufacturingFrom Pharmpedia

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Contents[hide]

1Introductiono 1.1Cappingo 1.2Lamination / Laminatingo 1.3Chippingo 1.4Crackingo 1.5Sticking / Filmingo 1.6Pickingo 1.7Bindingo 1.8Mottlingo 1.9Doubleimpression2Problemsandremedies fortabletcoatingo 2.1Blisteringo 2.2Chippingo 2.3Crateringo 2.4Pickingo 2.5Pittingo 2.6Bloomingo 2.7Blushingo 2.8Colour variationo 2.9Infillingo 2.10Orangepeel/Roughnesso 2.11Cracking/Splitting3KeyPhrases

Introduction(62,63)

Anidealtabletshouldbe free fromany visualdefector functionaldefect. Theadvancements

andinnovationsintabletmanufacturehavenotdecreasedtheproblems,oftenencounteredintheproduction,insteadhaveincreasedtheproblems,mainlybecauseofthecomplexities

oftabletpresses;and/orthegreaterdemandsof quality.

Anindustrialpharmacistusuallyencountersnumberofproblemsduringmanufacturing.Majorityof visualdefectsareduetoinadequate finesorinadequatemoistureinthegranules

ready forcompressionordueto faultymachinesetting. Functionaldefectsaredueto faulty

formulation.Solvingmanyofthemanufacturingproblemsrequiresanindepthknowledgeofgranulationprocessingandtabletpresses,andisacquiredonlythroughanexhaustive

studyandarichexperience.

Here,wewilldiscusstheimperfections foundintabletsalongwiththeircausesandrelatedremedies. Theimperfectionsareknownas: VISUALDEFECTSandtheyareeitherrelatedto

imperfectionsinanyoneormoreofthe following factors:


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I. TabletingProcess

II.Excipient

III.Machine

The defects related to Tableting Process are as follows:

i)CAPPING:Itispartialorcompleteseparationofthetoporbottomoftabletdueair-entrapmentinthegranularmaterial.

ii)LAMINATION:Itisseparationoftabletintotwoormorelayersduetoair-entrapmentinthegranularmaterial.

iii)CRACKING:Itisduetorapidexpansionoftabletswhendeepconcavepunchesareused.

The defects related to Excipient are as follows:

iv)CHIPPING:Itisdueto verydrygranules.

v)STICKING:Itistheadhesionofgranulationmaterialtothediewall

vi)PICKING:Itistheremovalofmaterial fromthesurfaceoftabletanditsadherancetothe faceofpunch.

vii)BINDING

Theseproblems(v, vi, vii)areduetomoreamountofbinderinthegranulesorwetgranules.

The defect related to more than one factor:

viii)MOTTLING:Itiseitherduetoanyoneormoreofthese factors:Duetoacoloured

drug,whichhasdifferentcolourthantherestofthegranularmaterial?(Excipient-related);

impropermixingofgranularmaterial(Process-related);dirtinthegranularmaterialoron

punch faces;oilspotsbyusingoilylubricant.The defect related to Machine

ix)DOUBLEIMPRESSION:Itisdueto freerotationofthepunches,whichhavesomeengravingonthepunch faces.

Further,inthissection,eachproblemisdescribedalong-withitscausesandremedieswhich

mayberelatedtoeitherof formulation(granulation)orofmachine(dies,punchesandentiretabletpress).

Capping

(1,5)

Cappingisthetermused,whentheupperorlowersegmentofthetabletseparateshorizontally,eitherpartiallyorcompletely fromthemainbodyofatabletandcomesoffasacap,duringejection fromthetabletpress,orduringsubsequenthandling.

Reason:Cappingisusuallyduetotheairentrapmentinacompactduringcompression,

andsubsequentexpansionoftabletonejectionofatablet fromadie.

TABLE.27. THECAUSES AND REMEDIESOF CAPPING RELATED TO FORMULATION

(GRANULATION)


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Sr.No.

CAUSES REMEDIES

1.Largeamountof finesinthegranulation

Removesomeorall finesthrough100to200meshscreen

2.Toodryor verylowmoisturecontent(leadingtolossofproper

bindingaction).

Moistenthegranulessuitably. Addhygroscopicsubstancee.g.:sorbitol,methyl-celluloseorPEG-

4000.

3. Notthoroughlydriedgranules. Drythegranulesproperly.

4.Insufficientamountofbinderor

improperbinder.

IncreasingthemountofbinderOR

Addingdrybindersuchaspre-gelatinizedstarch,

gumacacia,powderedsorbitol,PVP,hydrophilic

silicaorpowderedsugar.

5. Insufficientorimproperlubricant.Increasetheamountoflubricantorchangethe

typeoflubricant.

6.Granularmasstoocoldto

compress firm.Compressatroomtemperature.

TABLE.28. THECAUSES AND REMEDIESOF CAPPING RELATED TO MACHINE(DIES,

PUNCHES AND TABLET PRESS)

Sr.No.

CAUSES REMEDIES

1. Poorly finisheddiesPolishdiesproperly.Investigateother

steelsorothermaterials.

2.Deepconcavepunchesorbeveled-edge

facesofpunches.Use flatpunches.

3.Lowerpunchremainsbelowthe faceof

dieduringejection.Makepropersettingoflowerpunchduring

ejection.

4. Incorrectadjustmentofsweep-offblade.Adjustsweep-offbladecorrectlyto

facilitateproperejection.

5. Highturretspeed.Reducespeedofturret(Increasedwell

time).

Lamination / Laminating

(1,5)

Definition: Laminationistheseparationofatabletintotwoormoredistincthorizontallayers.

Reason: Airentrapmentduringcompressionandsubsequentreleaseonejection.


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Theconditionisexaggeratedbyhigherspeedofturret.

TABLE.29. THECAUSES AND REMEDIESOF LAMINATION RELATED TO FORMULATION(GRANULATION)

Sr.No.

CAUSESREMEDIES

1. OilyorwaxymaterialsingranulesModifymixingprocess. Addadsorbentorabsorbent.

2.Toomuchofhydrophobiclubricante.g.:Magnesium-stearate.

Usealessamountoflubricantorchangethetypeoflubricant.

TABLE.30. TheCausesand RemediesofLaminationrelatedtoMACHINE(Dies,Punchesand

TabletPress)

Sr.No.

CAUSES REMEDIES

1.

Rapidrelaxationoftheperipheral

regionsofatablet,onejection fromadie.

Usetapereddies,i.e.upperpartofthedie

borehasanoutwardtaperof3to5.

2. RapiddecompressionUsepre-compressionstep. Reduceturretspeedandreducethe finalcompression

pressure.

Chipping

(1)

Definition: Chippingisdefinedasthebreakingoftabletedges,whilethetabletleavesthepressorduringsubsequenthandlingandcoatingoperations.

Reason:Incorrectmachinesettings,speciallymis-setejectiontake-off.

TABLE.31. THECAUSES AND REMEDIESOF CHIPPING RELATED TO FORMULATION

(GRANULATION) ARE AS FOLLOWS

Sr.No.

CAUSES REMEDIES

1. Stickingonpunch facesDrythegranulesproperlyorincreaselubrication.

2. Toodrygranules.Moistenthegranulestoplasticize. Addhygroscopicsubstances.

3.Toomuchbindingcauseschippingatbottom.

Optimizebinding,orusedrybinders.


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TABLE.32. THECAUSES AND REMEDIESOF CHIPPING RELATED TOMACHINE(DIES,PUNCHES AND TABLET PRESS)

Sr.No.

CAUSES REMEDIES

1.Grooveofdiewornatcompressionpoint.

Polishtoopenend,reverseorreplacethedie.

2.Barreleddie(centerofthediewiderthanends)

Polishthedietomakeitcylindrical

3.Edgeofpunch faceturnedinside/inward.

Polishthepunchedges

4.Concavitytoodeeptocompressproperly.

Reduceconcavityofpunch faces.Use flatpunches.

Cracking

(1)

Definition:Small, finecracksobservedontheupperandlowercentralsurfaceoftablets,or veryrarelyonthesidewallarereferredtoas Cracks.

Reason:Itisobservedasaresultofrapidexpansionoftablets,especiallywhendeepconcavepunchesareused.

TABLE.33. THECAUSES AND REMEDIESOF CRACKING RELATED TO FORMULATION

(GRANULATION)

Sr. No.CAUSESREMEDIES

1. Largesizeofgranules. Reducegranulesize. Add fines.

2. Toodrygranules.Moistenthegranulesproperlyandaddproper

amountofbinder.

3. Tabletsexpand. Improvegranulation. Adddrybinders.

4. Granulationtoocold. Compressatroomtemperature.

TABLE.34. THECAUSES AND REMEDIESOF CRACKING RELATED TOMACHINE(DIES,PUNCHES AND TABLET PRESS)

Sr. No.CAUSES REMEDIES

1. Tabletexpandsonejectionduetoairentrapment.Usetapereddie.

2. Deepconcavitiescausecrackingwhile Usespecialtake-off.


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removingtablets

Sticking / Filming

(1)

Definition: Stickingreferstothetabletmaterialadheringtothediewall.

Filmingisaslow formofstickingandislargelyduetoexcessmoistureinthegranulation.

Reason:Improperlydriedorimproperlylubricatedgranules.

TABLE.35. THECAUSES AND REMEDIESOF STICKING RELATED TO FORMULATION

(GRANULATION)

Sr.No.

CAUSES REMEDIES

1.Granulesnotdried

properly.

Drythegranulesproperly.Makemoistureanalysisto

determinelimits.

2.Toolittleorimproper

lubrication.Increaseorchangelubricant.

3. ToomuchbinderReducetheamountofbinderoruseadifferenttypeof

binder.

4.Hygroscopicgranular

material.Modifygranulationandcompressundercontrolled

humidity.

5. Oilyorwaymaterials Modifymixingprocess. Addanabsorbent.

6. Toosoftorweakgranules.Optimizetheamountofbinderandgranulationtechnique.

TABLE.36. THECAUSES AND REMEDIESOF STICKING RELATED TOMACHINE(DIES,



1. Concavitytoodeep forgranulation. Reduceconcavitytooptimum.

2. Toolittlepressure. Increasepressure.

3. Compressingtoo fast. Reducespeed.

Picking

(1)


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Definition: Pickingisthetermusedwhenasmallamountofmaterial fromatabletisstickingtoandbeingremovedoff fromthetablet-surfacebyapunch face.

Theproblemismoreprevalentontheupperpunch facesthanonthelowerones. The

problemworsens,iftabletsarerepeatedlymanufacturedinthisstationoftoolingbecauseof

themoreandmorematerialgettingaddedtothealreadystuckmaterialonthepunch face.

Reason:Pickingisofparticularconcernwhenpunchtipshaveengravingorembossingletters,aswellasthegranularmaterialisimproperlydried.

TABLE.37. THECAUSES AND REMEDIESOF PICKING RELATED TO FORMULATION

(GRANULATION)

Sr.No.

CAUSES REMEDIES

1. Excessivemoistureingranules.Dryproperlythegranules,determine

optimumlimit.

2. Toolittleorimproperlubrication.

Increaselubrication;usecolloidalsilicaasa

polishingagent,sothatmaterialdoesnot

clingtopunch faces.

3.

Lowmeltingpointsubstances,may

soften fromtheheatofcompressionandleadtopicking.

Addhighmelting-pointmaterials.Usehigh

metingpointlubricants.

4.Lowmeltingpointmedicamentinhighconcentration.

Refrigerategranulesandtheentiretabletpress.

5. Toowarmgranuleswhencompressing.Compressatroomtemperature.Coolsufficientlybeforecompression.

6. Toomuchamountofbinder.

Reducetheamountofbinder,changethe

typeorusedrybinders.

TABLE.38. THECAUSES AND REMEDIESOF PICKING RELATED TOMACHINE(DIES,PUNCHES AND TABLET PRESS)

Sr.No.

CAUSES REMEDIES

1. Roughorscratchedpunch faces. Polish facestohighluster.

2.Embossingorengravinglettersonpunch facessuchasB, A,O, R,P, Q,G.

Designletteringaslargeaspossible.

Platethepunch faceswithchromiumtoproduceasmoothandnon-adherent face.

3. Bevelsordividinglinestoodeep. Reducedepthsandsharpness.

4.Pressureappliedisnotenough;toosoft

tablets.Increasepressuretooptimum.


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Binding

(1)

Definition: Bindinginthedie,isthetermusedwhenthetabletsadhere,seizeortearinthedie. A filmis formedinthedieandejectionoftabletishindered.Withexcessivebinding,thetabletsidesarecrackedanditmaycrumbleapart.

Reason:Bindingisusuallyduetoexcessiveamountofmoistureingranules,lackoflubricationand/oruseofworndies.

TABLE.39. THECAUSES AND REMEDIESOF BINDING RELATED TO FORMULATION

(GRANULATION)

Sr.No.

CAUSES REMEDIES

1.Toomoistgranulesandextrudes

aroundlowerpunch.Drythegranulesproperly.

2. Insufficientorimproperlubricant.

Increasetheamountoflubricantoruseamore

effectivelubricant.

3. Toocoarsegranules.Reducegranularsize,addmore fines,and

increasethe quantityoflubricant.

4.Toohardgranules forthelubricant

tobeeffective.Modifygranulation. Reducegranularsize.

5.Granularmaterial veryabrasiveandcuttingintodies.

Ifcoarsegranules,reduceitssize.

Usewear-resistantdies.

6.Granularmaterialtoowarm,sticks

tothedie.

Reducetemperature.

Increaseclearanceifitisextruding.

TABLE.40. THECAUSES AND REMEDIESOF BINDING RELATED TOMACHINE(DIES,


Sr.No.

CAUSES REMEDIES

1. Poorly finisheddies. Polishthediesproperly.

2.Roughdiesduetoabrasion,

corrosion.

Investigateothersteelsorothermaterialsor

modifygranulation.

3. Undersizeddies. Toolittleclearance.

Reworktopropersize.Increaseclearance.

4.Toomuchpressureinthetablet

press.

Reducepressure.OR

Modifygranulation.


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Mottling

(1)

Definition: Mottlingisthetermusedtodescribeanunequaldistributionofcolouronatablet,withlightordarkspotsstandingoutinanotherwiseuniformsurface.

Reason:Onecauseofmottlingmaybeacoloureddrug,whosecolourdiffers fromthecolourofexcipientsused forgranulationofatablet.

TABLE.41. THECAUSES AND REMEDIESOF MOTTLING

Sr.No.

CAUSES REMEDIES

1.

A coloureddrugusedalong

withcolourlessorwhite-

colouredexcipients.

Useappropriatecolourants.

2.A dyemigratestothesurface

ofgranulationwhiledrying.

Changethesolventsystem,

Changethebinder,

Reducedryingtemperatureand

Useasmallerparticlesize.

3.Improperlymixeddye,

especiallyduring Direct

Compression.

Mixproperlyandreducesizeifitisofalargersizetopreventsegregation.

4.Impropermixingofacolouredbindersolution.

Incorporatedrycolouradditiveduringpowderblending

step,thenadd finepowderedadhesivessuchasacaciaandtragacanthandmixwelland finallyaddgranulating

liquid.

Double impression

(1)

Definition: DoubleImpressioninvolvesonlythosepunches,whichhaveamonogramorotherengravingonthem.

Reason: Atthemomentofcompression,thetabletreceivestheimprintofthepunch.Now,onsomemachines,thelowerpunch freelydropsandtravelsuncontrolled forashortdistancebeforeridinguptheejectioncamtopushthetabletoutofthedie,nowduringthis

freetravel,thepunchrotatesandatthispoint,thepunchmaymakeanewimpressiononthebottomofthetablet,resultingin DoubleImpression.

Iftheupperpunchisuncontrolled,itcanrotateduringtheshorttraveltothe final

compressionstageandcreateadoubleimpression.

TABLE.42. THECAUSES AND REMEDIESOF DOUBLEIMPRESSION

Sr.No.

CAUSE REMEDIES

1. Freerotationofeitherupper -Usekeyingintooling,i.e.insetakeyalongsideof


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punchorlowerpunchduringejectionofatablet.

the punch,sothatit fitsthepunchandpreventspunchrotation.

-Newerpresseshaveanti-turningdevices,whichpreventpunchrotation.

Problems and remedies for tablet coating

Blistering

(1,64)

Definition:Itislocaldetachmentof film fromthesubstrate formingblister.

Reason:Entrapmentofgasesinorunderneaththe filmduetooverheatingeitherduringsprayingorattheendofthecoatingrun.

TABLE.43. THECAUSE AND REMEDYOF BLISTERING

Sr.No.

CAUSE REMEDY

1.Effectoftemperatureonthestrength,elasticityand

adhesionofthe film.Usemilddrying

condition.

Chipping

(1,64)

Definition:Itisdefectwherethe filmbecomeschippedanddented,usuallyattheedgesofthetablet.

Reason:Decreasein fluidizingairorspeedofrotationofthedruminpancoating.

TABLE.44. THECAUSE AND REMEDYOF CHIPPING

Sr.No.

CAUSE REMEDY

1.

Highdegreeofattritionassociatedwiththecoatingprocess. Increasehardnessofthe filmbyincreasingthe

molecularweightgradeofpolymer.

Cratering

(1,64)

Definition:Itisdefectof filmcoatingwhereby volcanic-likecratersappearsexposingthetabletsurface.

Reason: Thecoatingsolutionpenetratesthesurfaceofthetablet,oftenatthecrownwherethesurfaceismoreporous,causinglocalizeddisintegrationofthecoreanddisruptionofthe

coating.


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TABLE.45. THECAUSES AND REMEDIESOF CRATERING

Sr.No.

CAUSES REMEDIES

1.Inefficientdrying.

Useefficientandoptimumdryingconditions.

2.Higherrateofapplicationofcoatingsolution.

Increase viscosityofcoatingsolutiontodecreasesprayapplicationrate.

Picking

(1,64)

Definition:Itisdefectwhereisolatedareasof filmarepulledaway fromthesurfacewhenthetabletstickstogetherandthenpart.

Reason:Conditionssimilartocrateringthatproducesanoverlywettabletbedwhereadjacenttabletscansticktogetherandthenbreakapart.

TABLE.46. THECAUSES AND REMEDIESOF PICKING

Sr.

No.CAUSE REMEDY

1. Inefficientdrying.Useoptimumandefficientdryingconditionsorincrease

theinletairtemperature.

2.Higherrateofapplicationof

coatingsolution

Decreasetheraterofapplicationofcoatingsolutionby

increasing viscosityofcoatingsolution.

Pitting

(1,64)

Definition:Itisdefectwherebypitsoccurinthesurfaceofatabletcorewithoutany visibledisruptionofthe filmcoating.

Reason: Temperatureofthetabletcoreisgreaterthanthemeltingpointofthematerials

usedinthetablet formulation.TABLE.47. THECAUSE AND REMEDYOF PITTING

Sr.No.

CAUSE REMEDY

1. Inappropriatedrying Dispensingwithpreheatingproceduresattheinitiationof


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(inletair)temperature

coatingandmodifyingthedrying(inletair)temperaturesuchthatthetemperatureofthetabletcoreisnotgreaterthanthe

meltingpointofthebatchofadditivesused.

Blooming

(1,64)

Definition:Itisdefectwherecoatingbecomesdullimmediatelyorafterprolongedstorageathightemperatures.

Reason:Itisduetocollectiononthesurfaceoflowmolecularweightingredientsincludedinthecoating formulation.Inmostcircumstancestheingredientwillbeplasticizer.

TABLE.48. THECAUSE AND REMEDYOF BLOOMING

Sr.No.

CAUSE REMEDY

1.

Highconcentrationandlow

molecularweightofplasticizer. Decreaseplasticizerconcentrationandincreasemolecularweightofplasticizer.

Blushing

(1,64)

Definition:Itisdefectbestdescribedaswhitishspecksorhazinessinthe film.

Reason:Itisthoughttobeduetoprecipitatedpolymerexacerbatedbytheuseofhighcoatingtemperatureatorabovethethermalgelationtemperatureofthepolymers.

TABLE.49. THECAUSES AND REMEDIESOF BLUSHING

Sr.No.

CAUSES REMEDIES

1. HighcoatingtemperatureDecreasethedryingairtemperature

2.

Useofsorbitolin formulationwhichcauseslargestfallinthethermalgelationtemperatureofthe

HydroxyPropylCellulose, HydroxyPropylMethyl

Cellulose,MethylCelluloseandCelluloseethers.

Avoiduseofsorbitolwith HydroxyPropylCellulose, HydroxyPropyl

MethylCellulose,MethylCellulose

andCelluloseethers.

Colour variation

(1,64)

Definition: A defectwhichinvolves variationincolourofthe film.


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Reason: Alterationofthe frequencyanddurationofappearanceoftabletsinthesprayzoneorthesize/shapeofthesprayzone.

TABLE.50. THECAUSE AND REMEDYOF COLOUR VARIATION

Sr.No.

CAUSE REMEDY

1.

Impropermixing,unevenspraypattern,insufficientcoating,migrationofsoluble

dyes-plasticizersandotheradditivesduringdrying.

Go forgeometricmixing,reformulation

withdifferentplasticizersandadditivesorusemilddryingconditions.

Infilling

(1,64)

Definition:Itisdefectthatrenderstheintagliationsindistinctness.

Reason:Inabilityof foam, formedbyairsprayingofapolymersolution,tobreak. The foam

dropletsonthesurfaceofthetabletbreakdownreadilyduetoattritionbuttheintagliationsformaprotectedareaallowingthe foamtoaccumulateand set.Oncethe foamhas

accumulatedtoalevelapproachingtheoutercontourofthetabletsurface,normalattritioncanoccurallowingthestructuretobecoveredwithacontinuous film.

TABLE.51. THECAUSE AND REMEDYOF INFILLING

Sr.No.

CAUSE REMEDY

1.Bubbleor foam formationbecauseofairsprayingofapolymersolution

Addalcoholorusespraynozzlecapableof fineratomization.

Orange peel/Roughness

(1,64)

Definition:Itissurfacedefectresultinginthe filmbeingroughandnonglossy. Appearanceissimilartothatofanorange.

Reason:Inadequatespreadingofthecoatingsolutionbeforedrying.

TABLE.52. THECAUSES AND REMEDIESOF ORANGEPEEL/ROUGHNESS


1. RapidDrying Usemilddryingconditions

2. Highsolution viscosityUseadditionalsolventstodecrease viscosityofsolution.

Cracking/Splitting

(1,64)


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Definition:Itisdefectinwhichthe filmeithercracksacrossthecrownofthetablet(cracking)orsplitsaroundtheedgesofthetablet(Splitting)

Reason:Internalstressinthe filmexceedstensilestrengthofthe film.

TABLE.53. THECAUSE AND REMEDYOF CRACKING/SPLITTING

Sr. No.CAUSE REMEDY

1.Useofhighermolecularweight

polymersorpolymericblends.

Uselowermolecularweightpolymersorpolymeric

blends. Alsoadjustplasticizertypeandconcentration.

Key Phrases

y Duringtabletmanufacture,anindustrialpharmacistusuallyencountersmanyproblems.Solvingtheseproblemsrequiresanin-depth

knowledgeoftablet-formulationaswellasmachine-operating

processes.

y CappingandLaminationarethedefectsarisingasaresultofair-entrapmentinthegranularmaterial.

y Chippingisadefectrelatedarisingdueto verydrygranules.y Crackingisduetorapidexpansionoftablets,whendeepconcave

punchesareused.

y Sticking,PickingandBindingaretheimperfectionsrelatedtomoreamountofbinderingranules.

y Mottlingisanimperfectionarisingduetomorethanone factor:acoloureddrug,dirtingranulesortheuseofanoilylubricant.

y Double-Impressionisrelatedtoamachinedefect:itiscausedbythefreerotationofpunchesthathavesomeengravingonthepunch-faces.


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Coating defects:

y Blisteringisrelatedtoentrapmentofgasesinorunderneaththe filmduetooverheatingeitherduringsprayingorattheendofthecoating

run.Useofmilddryingconditionscansolvethisproblem.

y Chippingisrelatedtohigherdegreeofattritionassociatedwiththecoatingprocess.Increaseinhardnessofthe filmbyincreasingthe

molecularweightgradeofpolymercansolvethisproblem.

y Crateringisrelatedtopenetrationofthecoatingsolutionintothesurfaceofthetablet,oftenatthecrownwherethesurfaceismore

porous,causinglocalizeddisintegrationofthecoreanddisruptionof

thecoating.Decreaseinsprayapplicationrateanduseofoptimum

andefficientdryingconditionscansolvethisproblem.

y Pittingisdefectinwhichtemperatureofthetabletcoreisgreaterthanthemeltingpointofthematerialsusedintablet formulation.

Dispensingwithpreheatingproceduresattheinitiationofcoatingand

modifyingthedrying(inletair)temperaturecansolvethisproblem.

y Bloomingordull filmisgenerallybecauseofhigherconcentrationandlowermolecularweightofplasticizer.Souselowerconcentrationand

highermoleculargradeofplasticizer.

y Blushing/Whitishspecks/Hazinessofthe filmisrelatedtoprecipitationofpolymerexacerbatedbytheuseofhighcoatingtemperatureator

abovethethermalgelationtemperatureofthepolymers.

y Colour variationisbecauseofimpropermixing,unevenspraypattern,insufficientcoatingormigrationofsolubledyesduringdrying.

Geometricmixing,milddryingconditionsandreformulationwith

differentplasticizerscansolvethisproblem.

y Infillingisbecauseofbubble/foam formationduringairsprayingofapolymersolution. Additionofalcoholoruseofspraynozzlecapableof

fineratomizationcansolvethisproblem.

y Orangepeel/Roughnessisrelatedtoinadequatespreadingofthecoatingsolutionbeforedrying.Sodecreasein viscosityofcoating

solutioncancounterthisdefect.


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