Processing Problems Of Tablets

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Study notes containg important points on tablets processing problems such as tablet capping,tablet sticking,Tablet mottling, and tablet weight variation

CAPPING AND LAMINATION
PICKING AND STICKING
WEIGHT VARIATION
MOTTLING
DOUBLE IMPRESSION

CAPPING AND LAMINATION

• Capping:- Partial or complete separation of top or bottom
  crowns of tablet main body.
• Lamination:- Separation of a tablet into two or more distinct
  layers.
• Friability test can be used to reveal these problems

PICKING AND STICKING

Picking:-

Adherence of the tablet material from the surface of a tablet by a punch

Reasons:
• 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
Remedies:
• 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

Sticking:-

Adherence of tablet material to the die walls resulting in chipping of tablet
edges producing rough edges and causing the lower punches uneasy to move resulting
in damage of cam tracks and punch faces
Reasons:
• 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
Remedies:
• 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

WEIGHT VARIATION

Granule size and size distribution

Reasons:
• 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

Reasons:
• 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

Reasons:
• 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

Reason:
• 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

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

MOTTLING

Unequal distribution of colour on the tablet surface with light and dark areas
standing out in an otherwise uniform coloured surface
Reasons:
• 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
• Uneven distribution of colored adhesive gel solutions resulting in precipitation
Remedies:
• 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 to 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

DOUBLE IMPRESSION

Reason:
Uncontrolled movement of punches with engravings on them
Remedy:
Using anti-turning devices