Types of Tablet Defects with Causes and Remedies

Types of Tablet Defects with Causes and Remedies

Tablet defects can come from any of the unit operation upstream and from the tablet press. The raw materials may be of poor quality or do not meet specification, causing excessive fines that lead to a host of defects.


An ideal tablet should be free from any visual or functional defect. Majority of visual defects are due to inadequate fines or inadequate moisture in the granules ready for compression or due to faulty machine settings. Functional defects are due to faulty formulation


Classification or Types of Tablet Defects


Based on the relation of the defects and tablet, the tablets defects can be classified as: 

  • Defects related to tabletting process, 
  • Defects related to excipients,
  • Defects related to a Machine, and
  • Defects related to more than one factor.


These 4 are further classified as follows:

  • Defects related to tabletting process: Capping, Lamination, Cracking.
  • Defects related to excipients: Chipping, Sticking, Picking, Binding.
  • Defects related to a machine: Double Impression.
  • Defects related to more than one factor: Mottling.


Further details of each type of the tablet defects are explained below, with definitions, as well as causes and remedies.


#01 Defects Related to Tabletting Process


1. Capping

It is a partial or complete separation of the top or bottom of a tablet from the main body of a tablet and comes off as a cap, during ejection from the tablet press, or during subsequent handling.


Major Reason: Due air-entrapment in the granular material.


Causes and Remedies:

Capping Related to Formulation

Causes Remedies
Large amount of fines in the granulation. Remove some or all fines through 100 to 200 mesh screen.
Too dry or very low moisture content (leading to loss of proper binding action). Moisten the granules suitably. Add hygroscopic substance e.g.: sorbitol, methyl- cellulose or PEG-4000.
Not thoroughly dried granules. Dry the granules properly.
Insufficient amount of binder or improper binder. Increasing the amount of binder. (Or) Adding dry binder such as pre-gelatinized starch, gum acacia, powdered sorbitol, PVP, hydrophilic silica or powdered sugar.
Insufficient or improper lubricant. Increase the amount of lubricant or change the type of lubricant.
Granular mass too cold. Compress at room temperature.

Capping Related to Machine (Dies, Punches and Tablet Press)

Causes Remedies
Poorly finished dies. Polish dies properly. Investigate other steels or other materials.
Deep concave punches or beveled-edge faces of punches. Use flat punches.
Lower punch remains below the face of die during ejection. Make proper setting of lower punch during ejection.
Incorrect adjustment of sweep-off blade. Adjust sweep-off blade correctly to facilitate proper ejection.
High turret speed. Reduce speed of turret (Increase dwell time).

2. Lamination

It is the separation of a tablet into two or more distinct horizontal layers.


Major Reason: Air entrapment during compression and subsequent release on ejection. The condition is exaggerated by the higher speed of the turret.


Causes and Remedies:

Lamination Related To Formulation

Causes Remedies
Oily or waxy materials in granules. Modify mixing process. Add adsorbent or absorbent.
Too much of hydrophobic lubricant. Eg. Magnesium-stearate. Use a less amount of lubricant or change the type of lubricant.

Lamination Related To Machine (Dies, Punches and Tablet Press)

Causes Remedies
Rapid relaxation of the peripheral regions of a tablet, on ejection from a die. Use tapered dies, i.e. upper part of the die bore has an outward taper of 3° to 5°.
Rapid decompression. Use pre-compression step. Reduce turret speed and reduce the final compression pressure.

3. Cracking

Small, fine cracks observed on the upper and lower central surface of tablets, or very rarely on the sidewall are referred to as 'Cracks'.


Major Reason: It is observed as a result of rapid expansion of tablets, especially when deep concave punches are used.


Causes and Remedies:

Cracking Related To Formulation

Causes Remedies
Large size of granules. Reduce granule size. Add fines.
Too dry granules. Moisten the granules properly and add proper amount of binder.
Tablets expand. Improve granulation. Add dry binders.
Granulation too cold. Compress at room temperature.

Cracking Related To Machine (Dies, Punches And Tablet Press)

Causes Remedies
Tablet expands on ejection due to air entrapment. Use tapered die.
Deep concavities cause cracking while removing tablets. Use special take-off.

#02 Defects Related to Excipients


1. Chipping

Chipping is defined as the breaking of tablet edges, while the tablet leaves the press or during subsequent handling and coating operations.


Major Reason: Incorrect machine settings, specially mis-set ejection take-off.


Causes and Remedies:

Chipping Related To Formulation

Causes Remedies
Sticking on punch faces. Dry the granules properly or increase lubrication.
Too dry granule. Moisten the granules to plasticize.
Too much binding causes chipping at bottom. Add hygroscopic substances.

Chipping Related To Machine (Dies, Punches And Tablet Press)

Causes Remedies
Groove of die worn at compression point. Polish to open end, reverse or replace the die.
Barreled die (center of the die wider than ends). Polish the die to make it cylindrical.
Edge of punch face turned inside/inward. Polish the punch edges
Concavity too deep to compress properly. Reduce concavity of punch faces. Use flat punches.

2. Sticking or Filming

Sticking is the adherence of tablet material to the faces of tablet press punches or dies after compression. In sticking, the tablet surface sticks to the lower punch face but a small portion from the tablet surface is not detached or the pitted surface will not occur.


Major Reason: Improperly dried or improperly lubricated granules.


Causes and Remedies:

Sticking Related To Formulation

Causes Remedies
Granules not dried properly. Dry the granules properly. Make moisture analysis to determine limits.
Too little or improper lubrication. Increase or change lubricant.
Too much binder. Reduce the amount of binder or use a different type of binder.
Hygroscopic granular material. Modify granulation and compress under controlled humidity.
Oily or way materials. Modify mixing process. Add an absorbent.
Too soft or weak granules. Optimize the amount of binder and granulation technique.

Sticking Related To Machine (Dies, Punches And Tablet Press)

Causes Remedies
Concavity too deep for granulation. Reduce concavity to optimum.
Too little pressure. Increase pressure.
Compressing too fast. Reduce speed.

3. Picking

Picking is the term used when a small amount of material from a tablet is sticking to and being removed off from the tablet-surface by a punch face. The problem is more prevalent on the upper punch faces than on the lower ones.


Major Reason: Picking is of particular concern when punch tips have engraving or embossing letters, as well as the granular material is improperly dried.


Causes and Remedies:

Picking Related To Formulation

Causes Remedies
Excessive moisture in granules. Dry properly the granules, determine optimum limit.
Too little or improper lubrication. Increase lubrication; use colloidal silica as a ‗polishing agent‘, so that material does not cling to punch faces.
Low melting point substances, may soften from the heat of compression and lead to picking. Add high melting-point materials. Use high meting point lubricants.
Low melting point medicament in high concentration. Refrigerate granules and the entire tablet press.
Too warm granules when compressing. Compress at room temperature. Cool sufficiently before compression.
Too much amount of binder. Reduce the amount of binder, change the type or use dry binders.

Picking Related To Machine (Dies, Punches And Tablet Press)

Causes Remedies
Rough or scratched punch faces. Polish faces to high luster. Design lettering as large as possible. Plate the punch faces with chromium to produce a smooth and non-adherent face.
Bevels or dividing lines too deep. Reduce depths and sharpness.
Pressure applied is not enough; too soft tablets. Increase pressure to optimum.

4. Binding

Binding in the die, is the term used when the tablets adhere, seize or tear in the die. A film is formed in the die and ejection of the tablet is hindered. With excessive binding, the tablet sides are cracked and it may crumble apart.


Major Reason: Binding is usually due to excessive amounts of moisture in granules, lack of lubrication and/or use of worn dies.


Causes and Remedies:

Binding Related To Formulation

Causes Remedies
Too moist granules and extrudes around lower punch. Dry the granules properly.
Insufficient or improper lubricant. Increase the amount of lubricant or use a more effective lubricant.
Too coarse granules. Reduce granular size, add more fines, and increase the quantity of lubricant.
Too hard granules for the lubricant to be effective. Modify granulation. Reduce granular size.
Granular material very abrasive and cutting into dies. If coarse granules, reduce its size.
Granular material too warm. Use wear-resistant dies.
Sticks to the die. Reduce temperature.

Binding Related To Machine

Causes Remedies
Poorly finished dies. Polish the dies properly.
Rough dies due to abrasion, corrosion. Investigate other steels or other materials or modify granulation.
Undersized dies. Too little clearance. Rework to proper size. Increase clearance.
Too much pressure in the tablet press. Reduce pressure. Or Modify granulation.

#03 Defects Related to More Than One Factor


1. Mottling

Mottling is the term used to describe an unequal distribution of colour on a tablet, with light or dark spots.


Major Reason: One cause of mottling may be a coloured drug, whose colour differs from the colour of excipients used for granulation of a tablet.


Causes and Remedies:

Causes Remedies
A coloured drug used along with colourless or white-coloured excipients. Use appropriate colourants.
A dye migrates to the surface of granulation while drying. Change the solvent system, Change the binder, Reduce drying temperature and Use a smaller particle size.
Improperly mixed dye, especially during Direct Compression. Mix properly and reduce size if it is of a larger size to prevent segregation.
Improper mixing of a coloured binder solution. Incorporate dry colour additive during powder blending step, then add fine powdered adhesives such as acacia and tragacanth and mix well and finally add granulating liquid.

#04 Defects Related to a Machine


1. Double Impression

Double impression is a machine related tablet defect where a monogram or engraving shape or break line/ score line or imprint or logo appears twice on the tablet surface.


Major Reason: Uncontrolled rotation of either upper punch or lower punch during ejection of a tablet.


Causes and Remedies:


Causes Remedies
Free rotation of either upper punch or lower punch during ejection of a tablet. Use keying in tooling, i.e. inset a key alongside of the punch, so that it fits the punch and prevents punch rotation.

Summary

Defects of Tablets or Types of Tablet Defects


References

1. SlideShare.net | Defects in Tablet.

2. Pharma Pathway | TABLET DEFECTS AND IT’S REMEDIES.

3. PharmaEducation | Tablet defects.

4. LFA Tablet Presses | Common Tablet Defects That Can Be Avoided Easily.


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