Common Tablet Compression Defects|Tablet Issues And Solution

Tablet compression problems or defects of the tablet during compression operation are the most common which are observed in all pharmaceutical industries during the tablet compression process.

It is a fact that all the beginners who recently joined the pharma industry and even some old ones are not aware of the reasons for these defects and are also not aware of the solution to solve these problems.

In this article, we will discuss almost all possible defects which may occur during tablet compression operation  and will also discuss the reasons for these problems and will discuss how to solve or troubleshoot these compression issues.

Common Tablet Compression Defects or Problems

Following may be the problems faced during tablet compression operation,

• Capping
• Lamination
• Chipping
• Sticking
• Picking
• Weight variation
• Friability Problem
• Hardness Problem
• Double Impression
• Rat hole
• Black Spots
• Binding In Die
• Aging Of Tablet

Why Do Tablet Defects Occur? Reasons For Tablet Defects

These defects or problems related to tablet compression may occur because of the following issues,

1. Formulation Related
2. Machine Related
3. Operator Related

1. Formulation Related  Issues

The main reason for problems faced during tablet compression operation may be the tablet formulation itself.

The poor formulation may result in almost all the defects which we had discussed in the upper portion.

Example

Try to understand the above statement  with a simple example of prolonged disintegration time by relating it with the formulation.

If our formulation contains too much binder then it will give strong binding to the granules which will take more time to disintegrate.

So our formulation should be well optimised to get good results during granulation and subsequently during compression operation.

2.0 Machine Related Issues

Tablet compression defects may also occur even if we have a good formulation and the reason may be the compression machine itself.

If Compression Machine settings are not well optimised, it results in tablet defects.

Example

Let’s try to understand the above statement by an example.

Weight variation is a common problem that may occur due to poor flow and poor flow may occur due to improper adjustment of the height of the hopper base in the feeder. 

3.0 Operator Related

One of the main reasons for problems during the tablet compression process is the untrained machine operator.We can not run our compression operation smoothly if our operators are not skilled and trained. 

Untrained operators result in reduction of machine efficiency,  increase the cost of operation and breakdown time may also be increased.

Also Read

GMP vs cGMP and 21 CFR.

Reasons & Solutions Of Common Tablet Compression Problems

Now we will discuss one by one the upper-given tablet defects,reasons and their solutions.

Capping

Tablet capping is one of the most common problems which is almost observed in all pharmaceutical industries.

Removal of crown edges of a tablet is known as capping.

Reasons For Tablet Capping

Following may be possible reasons for tablet capping,

Formulation Related

• Less amount of Binder in the formulation results in tablet capping due to weak binding of granules.
• More Fine in the final product may also result in tablet capping 
• Large size Granules result in improper die filling and may cause capping.
• Less Moisture Content is the major cause of tablet capping.
• A higher quantity of lubricant.
• Higher blending after lubrication.

Solution 

• Use the optimum concentration of the binder to give strength to the granules.
• More fine and less granules result in tablet capping so reduce the amount of fine produce by controlling the drying process in FBD and the sieving process in an oscillating granulator.
• Maintain a balance between grain to fine powder ratio.
• If the granules are too dry, moisten the granules.
• Use the optimum level of lubricant.
• Blending time after lubricant should be a minimum of 3-5 minutes.

Compression Machine & Tooling Related Reasons

Compression machine and tooling issues that may result in tablet capping are as follows,

• Deep concave tooling may result in tablet capping.
• Capping also occurs If we use worn-out dies.
• Too much pressure applied for compression also results in tablet capping.
• High compression machine speed also results in capping.
• Reduced dwell time also results in tablet capping.
• Air entrapment in granules during compression.
• Less upper punch penetration.
• Improper machine adjustment in which the lower punch position is low and does not eject the tablet properly.
• Improper adjustment of swipe off blade.

Solution

• Try to avoid the use of deep concave tooling.
• Properly finished dies and punches should be used.
• Reduce hardness and apply optimum compression pressure.
• Reduce compression machine speed to increase dwell time.
• Use dome head punches or rota heads to increase the dwell time.
• Use pre-compression to remove entrapped air.
• Use tapered dies to facilitate the removal of entrapped air.
• Increase upper punch penetration.
• Properly adjust the position of lower punches and ejection cam.
• Adjust the swipe off the blade.

Tablet Lamination

 Tablet lamination is a defect and is defined as,

The separationtion of the tablet into two or more layers is known as lamination.

NOTE

In the pharmaceutical industries, pharmacists and operators working there use the term capping for all defects like chipping, capping and lamination but technically there is a difference.

In capping only crown edges break.

In lamination, the tablet separates into two layers.

In chipping, upper or lower edges are chipped.

Formulation Related Reasons for Tablet Lamination

Following formulation related reasons may result in tablet lamination,

• Less amount of binder.
• Over drying.
• Less moisture content in granules.
• Oversized granules.
• Over lubrication.
• Over blending with lubricants.

Solution

• Add more binder in the formulation.
• Reduce the number of fine powders.
• Optimum drying.
• Moisten the granules.
• Reduce granule size.
• Use an optimum concentration of Lubricants and 3-5 minutes blending after addition of lubricants.
  

Machine Related Reasons for Tablet Lamination

Following Machine related reasons may result for  tablet lamination,

• High turret speed.
• High pressure or high tablet hardness.
• Deep concave punches.
• Air entrapment.
• Worn-out dies and punches.
• Less dwell time.
• Improper adjustment of lower punch and swipe of blade.

Solution

• Reduce machine speed.
• Reduce tablet hardness.
• Avoid the use of deep concave tooling.
• Use pre-compression and tapered dies.
• Use good quality tooling.
• Properly adjust the lower punch position and swipe off blade.

Also Read

100 MCQs to revise your pharmaceutical knowledge.

Tablet Chipping

Tablet chipping is a problem or defect  in which the edges of the tablet chip during tablet compression or coating operation.

Reasons For Tablet Chipping

• Worn out, punches and dies.
• The lower punches position is not adjusted properly.
• The highlight of the swipe off blade is high over the turret.
• High pan speed during tablet coating.

Solution

• Regularly inspect punches and dies.
• Adjust lower punches and swipe of blade.
• Use optimum coating pan speed.

Tablet Sticking and Picking

There is a difference between sticking and picking but the reasons for both problems are almost the same.

Sticking

Sticking is a tablet defect in which powder or granules stick to the surface of a punch or on the walls of dies.

Picking

Picking is a tablet compression defect where powders of granules stick to the logo or letters on the punches.

Formulation Related Reasons for Tablet Sticking & Picking

• Higher Moisture Content in the final product.
• More fine powder in the formulation.
• Hygroscopic material used in the formulation.
• Case Hardening.
• The less amount of lubricants in the formulation.

Solution

• Dry the granules properly.
• More fine in formulation sticks to the punch surface rather than with the tablet surface so increases the ratio of granules.
• Try to avoid the use of hygroscopic materials.
• Try to avoid case hardening.
• Increase the concentration of lubricants.

Machine Related Reasons for Tablet 

Sticking & Picking

Following are the machine related problems that may be the reasons for tablet sticking and picking,

• The punch tip surface is rough.
• Punch tip chromium coating is damaged.
• Die bore may become rough.
• Compression Pressure is low.
• Logo or letters on punch surface.

Solution

• Polish the punch tips.
• Do not use rough dies.
• Logos or letters on punch surfaces should not be too deep.
• The letter should not be too close.

Weight Variation

Weight variation is a common problem that may be observed during tablet compression operation and in this defect, the defined weight of individual tablets is not achieved and weight may become high or low from the defined ranges.

Formulation Related Reasons For Weight Variation

Following Maybe the formulation related reasons which may result in weight variation

• More fine powder in formulation results in poor flow and this poor product flow results in weight variation because dies are not filled properly. 
• If tablet size is small and granule size is large, it results in weight variation due to improper filling of dies.
• Higher levels of moisture content may result in the development of rat holes which results in weight variation.

Solution

• Try to reduce the amount of fine powder in the final product.
• Use optimum granule size.
• Properly dry the granules to prevent the development of rat holes.

Machine Related Reasons For Weight Variation

• If the height of the Hopper base is not adjusted properly it may result in weight variation.
• Weight variation may also occur due to blockage of any feeder housing.
• Weight variation may also occur if the feeding rate of powders or granules is slower than the machine speed.
• Punches are not of suitable length, meaning there may be a punch length variation.
• Lower punches may get stuck and hinder proper die filling.

Solution.

• Properly adjust the hopper.
• Carefully observe any blockage of feeder housing.
• The feeding rate should be according to the machine speed.
• Routinely monitor punch lengths.
• Properly clean the punches.
  

Tablet Friability Problem

Percentage weight loss is known as friability. Friability testing is done to check how hard a tablet is and to protect the tablets during transportation, coating and blistering operation.

Reasons

• Less binding of particles due to less amount of binder.
• Over dried granules.
• Too much pressure or high tablet hardness.
• The compression machine speed is too high.
• Higher amount of lubricants.
• Higher blending time with lubricants.
• Large granules size with less or no fine powder.
  

Solutions.

• Add more binder in the formulation.
• Moisten the granules.
• Reduce tablet hardness.
• Reduce compression machine speed.
• Use an optimum concentration of lubricants.
• Blending time with lubricants should be 3-5 minutes.
• Reduce the size of the granules.

Tablet Hardness Problem

Tablet hardness is one of the most important factors which is related to the strength of tablets and also affects drug dissolution profile.

Low Hardness

Following may be the possible reasons for low tablet hardness,

• Higher moisture content of granules.
• Over dried granules.
• Higher Compression Machine speed.
• Low tablet weight.
• Tablets are compressed in higher humidity areas.
• Too much fine powder in the formulation.
• Oversized granules.
• Higher amount of lubricant.
• Higher blending time with lubricants.
• Soft or fragile granules.
• Less kneading time.
• Less solvent addition for kneading.

Solution

• Keep optimum moisture content in granules.
• Reduce the compression machine speed to increase dwell time.
• Adjust tablet hardness.
• Maintain the humidity of the compression area.
• Adjust granules to fine powder ratio.
• Use an optimum concentration of lubricants.
• Blending time with lubricants should be optimum.
• Optimize kneading time.
• Optimize the quantity of solvent used for kneading.

Also Read

Potency calculation of Active pharmaceutical Ingredient.

Double Impression

The double impression is a defect in which embossing or bisect lines on the surface of a tablet are overlapped or appear as doubled.

Reason.

Free movement of lower punches.

Solution

Use keyed punches for tablet compression.

Rat Hole

Rathole during tablet compression operation is a defect in which powder in tablet compression machine hopper sticks to the walls and it hinders free movements of powders or granules as a result powder or granules from mid of hopper slowly flow forming a rat hole like structure known as rat hole or ratholing.

Reasons For Rat Holing

Possible reasons for ratholing are as follows,

• More fine powder in the formulation.
• Higher moisture content in the product.
• Less concentration of glidant in the formulation.
• Less concentration of lubricants.
• Improper adjustment of hopper base height.
• Use of a conventional feeding system or Lack of force-feeding system.

Solution For Rat Holing 

• Optimise granules to fine ratio.
• Dry the product.
• Use an optimum concentration of glidants and lubricants.
• Properly adjust the height of the hopper base to improve flow.
• Use a force-feeding system to facilitate powder or granule flow.

Black Spots During Tablet Compression

It’s a common problem in which black particles or spots are observed on the tablet surface.

Sometimes black particles are observed on the upper surface of the tablet and sometimes these are observed on both sides of the tablet

Reasons For Black Spots On Tablets

Following may be the possible reasons,

• Balck particles may be in some of the excipients used for manufacturing tablets.
• Higher moisture content results in the sticking of powder to the turret which then peels off and may result in black spots on the tablet surface.
• Rubbing of feeder over the turret.
• Excessive fines below the feeder may generate black particles due to friction.
• Lubrication oil may mix with powder or granules.
• Due to friction, lubrication applied on cams may burn and result in black spots.
• Black particles may be in granules during granulation due to granulator seal damage.
• Black particles may be in granules during granulation due to oil leakage from the granulator.
• Dry mill may shread or generate black particles.
• Formulations containing DCP may have black particles due to its cursive nature.
• Poor dust collection system during the tablet compression operation.
  

Solution

• Carefully sieve the excipients to remove any undesired particles.
• Properly dry the granules.
• Properly adjust the feeder of the compression machine.
• Use dust cups to collect lubrication oil dripping.
• Lubricate the cams at proper time intervals to prevent drying and burning.
• Carefully sieve the granules and observe any seal damage or oil leakage from the granulator.
• Maintenance of the dry mill and granulator should be done at defined intervals.
• Try to avoid the use of crusive materials.
• The dust collection system should be efficient.

Die Binding

Die binding is a defect in which powders or granules bind inside the die resulting in damaged tablets

Reasons

• Excessive moisture content in the final granulated product.
• Excessive fine.
• Less concentration of lubricants.
• Worn out, dies and punches.
• Hygroscopic materials in the product.

Solution

• Properly dry the granules.
• Improve powder to granule ratio.
• Use optimum concentration of lubricants.
• Use properly finished punches and dies.
• Process hygroscopic materials in a well-controlled environment.

Aging Of Tablets

Aging of the tablets is the defect in which the hardness of tablets is increased with time.

Reasons.

The following may be the reasons.

• Moisture in the granules.
• The water of crystallization may react with API or excipients.
  

Solution

• Properly dry the granules.
• Collect data at different temperature and humidity ranges during preformulation studies.

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