MOTTLING
Unequal distribution of colour on the tablet surface with light and dark areas standing out in an otherwise uniform coloured surface

Cause :
• Variation in the colours of ingredients (drug and other additives)
• Drugs with degradation nature and have different coloured degraded products
• Migration of dye to the surface of granulation during drying. At high temperature dyes are easily migrate to surface and spread to upper surface.
• Uneven distribution of colored adhesive gel solutions resulting in precipitation
• The improper size either large or small particles enhances color distribution. During preparation dyes are not properly mixed and not selected ideally or any incompatibility will tends to enhance appearance of color on tablet surface.
• Improper storage conditions.

Remedy:
• By using bright coloring agent that will mask all the color variations
of the ingredients
• Proper drying by reducing the drying temperature
• Colored adhesive gel solutions must be added when they are hot too much cooler powder mixtures to avoid precipitation
• It is better to incorporate fine powder adhesives like acacia and tragacanth into product before adding the granulating fluid
• By changing the solvent system or binder system
• Grinding to small particle size


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CAPPING and LAMINATING
CAPPING :
Capping Continuously high speed of tablet machine and high degree of compression setting makes tablet to separate main surface into individual surface. Avoid defective punches and dies. High temperature adjustment also favor capping. Distance between upper and lower punches will entrap air is bone factor for capping. Fine particles were susceptible than coarse particles will affect ideality of tablets. Capping minimized by keeping the feed material with cohesive nature.

LAMINATION :
Lamination It is major problem among of all defects. Occur upon storage period, or soon after compression. Air entrapment between layers of tablet. Low levels of binding agent. It minimized by improving lubricant concentration. Change the method of granulation. By direct compression technique it is prevented to some extent. Use always dry material (feed).

CausesRemedy
Air entrapment in the tablet among granules or among
particles
By pre-compression, Reducing final compression, Minimizing
tableting rate
Deformational properties of formulation during and after compressionIncreasing stress relaxation time
Improper/Deep concave punchesBetter to use flat punches
Over dried granules (Due to lack of cohesion)
By maintaining moisture levels using hygroscopic materials
like MC (Methyl Cellulose), Sorbitol, PEG 4000 (Polyethylene glycol) etc.

Improper tooling:
  • Concave edges of punches turning claw shaped
  • Greater radius of curvature of punch face
  • Dies developing a wear ring shape
  • Improper adjustment of sweep off blade
  • Less rise of lower punch during ejection of table

Proper tooling:
  • Checking of punches and replacing them
  • Proper checking and replacing them
  • Turning the die over so that compression occurs in an
    unworn area above ring
  • Proper setting of sweep off blade & lower punch rise
Poor compressibility observed during direct compression
technique
Relative compressibility is to be maintained


PICKING
Adherence of the tablet material from the surface of a tablet by a punch
Causes:
Because of engraving or embossing or debossing on the punch tips like small enclosed areas in the letters like “A”, “B”, “D”, “O”, “Q” etc

Remedy:
• Lettering should be designed as large as possible, even the tablet size can be increased by reformulation
• Colloidal silica can be added as polishing agent to formula
• Using additional binder to increase cohesiveness of granules and thereby causing decreased adherence
• Plating of punch faces with a chromium material to obtain smooth face which is non-adherent
• Avoid wet granules.

STICKING
Sticking always occurs in low melting point substances, and moisture supports this defects, lower the speed up of upper and lower punch leads to weight variation of tablets. It produces rough and chipping surface tablets. It develops material on both punches. Lack of drying is basis of this one.


Causes:
• Presence of low melting point substances in the formula ex. Stearic acid, PEG (Polyethylene glycol) etc , which gets soften due to compressive heat
• Excessive moisture in the granules

Remedy:
• Partial or complete substitution of low melting point components with high melting point materials in the formula
• Proper drying of the granules to remove excessive moisture
• Selection of Binding agent is essential to solve sticking.
• Ideal selection of lubricant in desired proportion will minimized this problem.

WEIGHT VARIATION (Granule size and size distribution)

Causes:
• Improper blending of granules
• Lack of sufficient of lubricant .
• Abnormal uniform mixing of all excipients.
• Improper tool setting of machine. Hi-speed running of machine.
• improper glidant selection.
• Improper drying making tablet with different weight.
• Proportion of small to large granules influence the die filling capacity and thereby results in weight variation of tablets
• If large granules are used to fill small die cavities, even a small difference in granules results in high percent weight variation of tablets

Remedies:
• Uniform size distribution (Narrow) and smaller granular size is preferable


POOR FLOW
Causes:
• Improper design of hopper
• Poor flow of granules
• Bridging/arching and rat-holing of granules at the bottom of the hopper
• Segregation or stratification of particles due to use of flow promoting
devices like vibrators
• Surges of excessive flow above the hopper
Remedies:
• Flow can be improved by using glidants like talc, colloidal silica etc.
• By proper design of the hopper
• By using flow enhancing devices like vibrators
• By preparing uniform sized and shaped granules

POOR MIXING
Causes:
• Improper mixing of ingredients like glidants and lubricants useful for
proper flow and punching
• Insufficient or inadequate time of mixing
Remedy:
• Proper mixing by maintaining adequate time and using suitable mixer

PUNCH VARIATION
Cause:
• Unequal lengths of lower punches which results in variations of granular
volume filled in die
Remedy:
• Proper tooling by using good and uniform sized punches

HARDNESS VARIATION
Causes:
• Due to weight variation in granules filled in die
• Space between lower and upper punches
Remedy:
• Proper tooling of machine

DOUBLE IMPRESSION
Cause:
Uncontrolled movement of punches with engravings on them
Remedy:
Using anti-turning devices


CHIPPED EDGE :
 Tablets having sharp edge, elongated tablets are prone to chipped edge. Granules are subject to high temperature will improve chipped surface (high drying). This defects accompanied with damaged surfaces at its corners of tablet ,easily fragmented by even smooth handling also. Due to rough handling. Tablet shape is abnormal than normal. Use optimum level of binding agent.

PRINT DEFECT :
 It is mainly observed in tablets which having hard corners/designs on punches. It takes due to improver punch cycle. Punches having rough surface . Improper blending of total powder. Letter are designed with uneven surfaces on punches.

HAIR/FIBRE :
HAIR/FIBRE As name itself indicates some unwanted particles/hair are appeared on tablet surface. Not following SOP. Operator not implementing cGMP. Lack of attention of operator. Punches are cleaned before installing in their respective places. Lack of cleaning/spacious rooms.

BLACK SPOT/STAIN :
Stains or spots will be appear on tablet surface. Migration of coloring agent upon storage. High temperature is key factor for penetration of dye into upper surface. Improper cleaning of punches. Mainly observed in colored tablets. Observe in high concentration of dyes. Incompatibility among excipients and API

SOFT TABLETS :
 The tablets are susceptible to hydrolysis will develop soft nature. Improper storage. Mainly observed in polymer/coated tablets. Lack of drying will enhance the softness. Granulation particles will completely free from moisture by keeping to drying condition properly. Soft tablet will form initiate/basis for sticking or picking defects. Use of lubricant that impart waxy nature. Application of low compaction pressure. The strength of bond is weakened across granules.

PROTRACTED DISINTEGRATION :
 Disintegration time is extended in tablet. Use of high compression on punches. Incorporation of lubricant in excess quantity. Overcome by using proper suitable surfactant concentration. Addition of more concentration of binding agent. Too low compression also favors extend disintegration time.


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