introduction

Seminar on DEFECTS IN TABLETSBYARJUN NARALAM.PHARMACY, I SEM

DEPARTMENT OF PHARMACEUTICSUNIVERSITY COLLEGE OF PHARMACEUTICAL SCIENCESKAKATIYA UNIVERSITYWARANGAL.CONTENTSIntroductionDefects in TabletsDefects in sugar coated tabletsDefects in film coated tabletsConclusionReferences

INTRODUCTION In the normal process of developing formulations, and in the routine manufacture of tablets, various defects are observed. Sometimes, the source of the problem or the defect is the formulation, the compression equipment, or a combination of the two.Some defects are noticed immediately during manufacturing but others may be noticed during storage as in the case of capping.

DEFECTS IN TABLETSCAPPING AND LAMINATIONPICKING AND STICKINGMOTTLINGDOUBLE IMPRESSIONSBLACK SPECKSCHIPPING AND SPLITTING

CAPPING AND LAMINATIONCapping is defined as the partial or complete separation of the top or bottom crowns of a tablet from the main body of the tablet.Lamination is the separation of a tablet into two or more distinct layers.These processing problems are readily apparent immediately after compression or may occur hours or even days later.Subjecting tablets to the friability test is the quickest way of revealing such problems.CAPPING AND LAMINATION

CAUSES AND CORRECTIVE ACTIONSAir entrapmentReduce press speedPrecompress granulationReduce quantity of fine particles in the granulationTaper diesEnsure that punch-to-die clearance is correctExcessive pressureReduce tablet weight and/or increase its thickness within allowable tolerancesAdjust pressure

CAUSES AND CORRECTIVE ACTIONSToo rapid expansion of tablet upon ejectionTaper diesPoor granulationIncrease quantity of binder; use strong binderExcessively dry granulationIncrease lubricantExcessive lubrication of granulationDecrease lubricant; blend all ingredients before adding lubricant

CAUSES AND CORRECTIVE ACTIONSPunch cavity too deepUse punches with less concave depthPunch tips worn Refurbish or replace punchesLower punch set too low at tablet take-offSet lower punch tip flush with top of dieTablet take-off bar set too highAdjust take-off bar

PICKING AND STICKINGPicking refers to a tablet material being removed from the tablets surface by a punch.It is of particular concern when punch tips have engraving or embossing.Tablet materials adhering to punches can accumulate to the point of obliterating the tip design.Sticking refers to a tablet material adhering to the die wall.It results in the buildup of material on punch faces.

CAUSES AND CORRECTIVE ACTIONSExcessive moistureCheck moisture content of granulation; dryingCheck room humidityPresence of low-melting-point substancesDilution with higher-melting-point materials Insufficient compaction forceReduce tablet weight and/or increase its thickness within allowable tolerancesInadequate lubrication of granulationCheck and/or adjust level of lubricant usedCAUSES AND CORRECTIVE ACTIONSPunch face condition: pits on punch faces and/or improper draft on embossingTry repolishing punch facesTry chrome-plating of punch faces

Poor embossing designRedesign embossing per TSM guidelines, or consult tooling supplier

MOTTLING Unequal distribution of color on a tablet, with light or dark areas standing out in an otherwise uniform surface. Causes and corrective actions:Drug whose color differs from the tablet excipients or a drug whose degradation products are colored.Use of colorantsMigration of dyes to the surface of granulation during dryingChange the solvent systemReduce the drying temperatureGrind to a small particle size CAUSES AND CORRECTIVE ACTIONSHigh moisture content of granulationDry granulationOversized granulation particlesReduce particle sizeContamination of granulation, usually by grease or oilCheck oil seals on upper punch guidesFit oil/dust caps to upper punchesReduce lubrication of upper punches to an acceptable levelContamination of granulation from chutes or feed hoppersClean and reset components correctly

DOUBLE IMPRESSIONThis problem is encountered with punches that have a monogram or other engraving on them.

Causes and corrective actions:Rotation of punchesAdjust antiturning devicesUse keyed punchesDIRT IN PRODUCT (BLACK SPECKS) : Dust,dirt,or press lubrication in the granulationClean press more frequentlyExcessive or wrong press lubricationUse proper punch dust capsRubbing of feeder components

CHIPPING OR SPLITTINGPoor surface finish on punch tips; worn punches and dies

Poor tooling design (e.g., sharp embossing or bisect lines)

Polish punch tips; replace punches and dies

DEFECTS IN SUGAR COATED TABLETSCHIPPING OF COATINGS: Sugar coatings are inherently brittle and thus prone to chipping if mishandled.Excessive use of insoluble fillers and pigments tends to increase the brittleness of sugar coatings.Avoid them where ever it is possibleAddition of small quantities of polymers(such as cellulosics,polyvinylpyrrolidine,acacia,or gelatin) to improve structural integrity.CRACKING OF COATINGS: Tablet cores that expand, either during or after coating, are likely to cause the coating to crack.Such expansion may result from1.Moisture absorption by the tablet core.2.By stress relaxation of the core after compaction.Moisture sorption can be minimized by appropriate use of seal coat.Expansion due to post compaction stress relaxation can be resolved by extending the time between the compaction event and commencement of sugar coating.TWINNING (OR BUILD OF MULTIPLES) By their very nature, sugar-coating formulations are very sticky, particularly as they begin to dry, and allow adjacent tablets to stick together.Build up of multiples really becomes a problem when the tablets being coated have flat surface which can easily come into contact with one another.Troublesome with high-dose, capsule-shaped tablets that have high edge walls.Appropriate choice in tablet punch design can be effectively used to minimize the problem.

UNEVEN COLOR Uneven distribution of color, particularly with the darker colors, is often visually apparent, and thus a major cause of batch rejection.Poor distribution of coating liquids during applicationUniform mixing of tablets in the coating processAddition of sufficient coating liquidsColor migration of water-soluble dyes while the coating is dryingChange the solvent systemReduce the drying temperatureGrind to a small particle sizeUnevenness of the surface of the subcoat Achieve desired surface smoothnessWashing back of pigment-colored color coatingsReplace aluminium lakesUse combinations of dyes and pigmentsExcessive drying between color applicationsReduce rate of dryingReduce drying temperature

BLOOMING AND SWEATING Residual moisture in finished sugar-coated tablets can often be a problem. over a period of time, this moisture can diffuse out and affect the quality of the product.Moderate levels of moisture egress cause the polish of the product to take on a fogged appearance, a phenomenon often termed blooming.At higher levels of moisture egress, the moisture may appear like beads of perspiration on the tablet surface, a phenomenon often termed sweating.Sweating can be much more serious, since tablets stored in closed containers will ultimately stick together.Obtain appropriate levels of moisture.

MARBLING

To achieve a high-quality, sugar coated product it is important to ensure that color is uniformly distributed in the color layer, and at the end of the application of the color coating that a smooth coating surface is obtained.Failure to achieve the requisite smoothness often results in a marbled appearance on polishing.This problem occurs as the result of the collection of wax in the small surface depressions of a rough coating and is particularly evident with darker colors.Check for smooth surface at the end of color coating.DEFECTS IN FILM COATED TABLETS PICKING:It results when the coating on two adjacent tablets is not sufficiently dry before contact between them occurs.As the partially dried coating is extremely tacky, once the two tablets make contact they adhere to one another.Once the coating has dried they break apart later under the influence of attrition.In extreme cases the tablets may become permanently glued together so that twinning occurs.Over wetting typically occurs when the spray rate is excessive for the drying conditions in the process.Adjust the spray rateAdjust the temperature of dryingCheck for the proper functioning of the spray gunsCertain types of coating formulations(e.g., those based on hydroxypropylcellulose, and several of the acrylic aqueous latex coating systems) are inherently tackier during application.Replace with other polymer systems.

ORANGE PEEL(ROUGHNESS)Inadequate spreading of the coating solution before drying causes a bumpy or orange-peel effect on the coating.This indicates that spreading is impeded by too rapid drying or by high solution viscosity.This is caused by process conditions which include low spray rates coupled with excessive drying conditions and use of excessive atomizing air pressures.Adjust the spray rate and drying conditionsCoating liquids with high viscositiesThinning the coating solution with additional solventsIn brief optimize the coating process.

EDGE WEAR(CHIPPING)Tablet edges are often exposed to attritional effects, so fracture at this point results in parts of the surface being exposed, referred as chipping.Seen with brittle film coatings that offer insufficient protection to tablet edges.Addition of small quantities of polymers(such as cellulosics,polyvinylpyrrolidine,acacia,or gelatin) to improve structural integrity.

FILM CRACKINGCracking of film coating occurs when the internal stress exceeds the tensile strength of the coating.The problem is exacerbated when significant differences exist between the thermal expansion coefficients for the core and coating.Totally unacceptable for products where the applied coating is a major factor in modifying drug-release characteristics.Minimize the internal stresses by adjusting the plasticizer type, pigment type and their concentration.Increase the tensile strength of the film by using high molecular-weight polymers or polymer blends.FILM PEELINGDuring application of aqueous coating formulations, cohesive failure(cracking) of the coating occurs.This coating may peel back from the surface of the substrate and result in peeling.Cohesive and adhesive failure( both linked to internal stress)Increase the tensile strength of the filmDecrease the internal stress

BRIDGING OF LOGOS(INTAGLIATIONS)This phenomenon occurs when a component of the internal stress becomes sufficiently high so as to cause partial or complete detachment of the coating ( from the substrate) in the region of logo.As a result of such detachment, the film is able to shorten and thus partially relieve the stress within the film.This defect can be so severe that the monogram or bisect is completely obscured.Improve film adhesion by adjusting plasticizer contentAppropriate design of tablet punches with respect to logo

IN-FILLING OF LOGOSIn-filling of logos typically occurs during the spray application of aerated aqueous film-coating solutions.When a foamy coating solution impinges on a regular part of the tablet surface it will, under the shear forces generated, form a film with normal characteristics.Those droplets of coating liquid that reside in the logo, being protected from shear forces at the surface, gradually dry to form a solid foam that eventually obliterates the bisect.Judicious monitoring of the fluid application rate and thorough mixing of the tablets in the pan prevent filling.BLISTERING

When coated tablets require further drying in ovens, too rapid evaporation of the solvent from the core and the effect of high temperature on the strength, elasticity, and adhesion of the film may result in blistering.

Use milder drying conditions. conclusionTablets are widely used dosage forms but defects in aesthetic appearance may lead to the rejection of their administration by the patient.From the manufacturer point of view these defects may lead to reworking or rejection of the batch.Although many of these defects may be purely cosmetic some of them are totally unacceptable.So a proper attention by the manufactuer on the source of defects and their orderly corrections is required.REFERENCESHerbert A. Lieberman, Leon Lachman, Joseph B. Schwartz, Pharmaceutical dosage forms : Tablets, Second Edition,vol 3.Herbert A. Lieberman Leon Lachman, Theory and Practice of Industrial Pharmacy, 2009.James Swarbrick, James C. Boylan, Encyclopedia of Pharmaceutical technology, Volume 15, 1996.James Swarbrick, Encyclopedia of Pharmaceutical technology, Third Edition, Volume 6, 2007.Website:www.pharmainfonet.com

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