|Tablet defects related to the tabletting process||Capping and Lamination|
|Tablet defects related to excipients||Chipping; Sticking; Picking and Binding|
|Tablet defects related to more than one factor||Mottling|
|Tablet defects related to machine||Double impression|
8 Types of Tablet Defects
A perfect tablet should be free of any visual or functional flaws. The advancements and innovations in tablet manufacturing have not reduced the problems that are frequently encountered in production but have instead increased the problems, owing to the complexities of tablet presses and/or higher quality demands.
During the manufacturing process, an industrial pharmacist frequently encounters a variety of issues. The majority of visual tablet defects are caused by insufficient fines or moisture in the granules ready for compression, or by faulty machine settings. Functional flaws are caused by poor formulation.
Many manufacturing problems require in-depth knowledge of granulation processing and tablet presses, which can only be obtained through extensive study and extensive experience.
In this section, we will go over the defects found in tablets, as well as the remedies for tablet defects. The flaws are referred to as visual defects, and they are caused by flaws in one or more of the factors.
Tablet processing issues can be caused by flaws in the formulation, compression equipment, or both. As a result, we can categorize the problems as follows:
Capping of Tablets
Capping is the term used when the upper or lower segment of a tablet separates horizontally, either partially or completely from the main body of the tablet and comes off as a cap, either during ejection from the tablet press or subsequent handling.
Capping is typically caused by air entrapment in a compact during compression, followed by tablet expansion upon the ejection of a tablet from a die.
- Pass some or all of the fines through a 100 to 200 mesh screen.
- Properly moisten the granules. Include a hygroscopic substance, such as sorbitol, methylcellulose, or PEG4000.
- Thoroughly dry the granules.
- Increasing the quantity of binder
- Including a dry binder like pre-gelatinized starch, acacia gum, powdered sorbitol, PVP, hydrophilic silica, or powdered sugar.
- Increase the amount of lubricant or switch to a different type of lubricant.
- Compress at room temperature.
- Polish dies properly. Look into other steels or materials.
- Make use of flat punches.
- Adjust the lower punch properly during ejection.
- Correctly adjust the sweep-off blade to ensure proper ejection.
- Slow down the turret (Increase dwell time).
Lamination of Tablets
The separation of a tablet into two or more distinct horizontal layers is known as lamination.
Reason- Air entrapment during compression, followed by release during ejection.
The condition is exacerbated by the turret’s increased speed.
- Change the mixing process. Adsorbent or absorbent should be added.
- Use less lubricant or switch to a different type of lubricant.
- Use tapered dies, which have an outward taper of 3° to 5° at the upper part of the die bore.
- Apply the pre-compression step. Reduce the turret speed and final compression pressure.
Chipping of Tablets
The breaking of tablet edges as the tablet leaves the press or during subsequent handling and coating operations is called chipping.
Reason: Incorrect machine settings, particularly an incorrectly set ejection take-off.
- Increase lubrication or dry the granules properly.
- To plasticize the granules, moisten them. Hygroscopic substances should be added.
- Improve the binding or use dry binders.
- Polish the die to open it up, reverse it, or replace it.
- To make the die cylindrical, polish it.
- The punch edges should be polished.
- Punch faces’ concavity should be reduced. Make use of flat punches.
Cracking of Tablets
Cracks are small, fine cracks found on the upper and lower central surfaces of tablets, and very rarely on the sidewall.
Reason: It is observed as a result of rapid tablet expansion, particularly when deep concave punches are used.
- Granule size should be reduced. Fines should be added.
- Moisten the granules thoroughly and add the appropriate amount of binder.
- Enhance granulation. Dry binders should be added.
- Compress at room temperature.
- Utilize a tapered die.
- Use a unique take-off.
Sticking of Tablets
The tablet material adhering to the die wall is referred to as sticking.
Reason- Filming is a slow type of sticking caused primarily by excess moisture in the granulation.
Granules that have been improperly dried or lubricated.
- Dry the granules thoroughly. To determine limits, conduct a moisture analysis.
- Increase or replace the lubricant.
- Reduce the amount of binder used, or switch to a different type of binder.
- Granulation should be modified and compressed under controlled humidity conditions.
- Change the mixing process. Include an absorbent.
- Optimize the binder amount and granulation technique.
- Optimize the concavity.
- Intensify the pressure.
- Reduce your speed.
Picking of Tablets
When a small amount of material from a tablet sticks to and is removed from the tablet’s surface by a punch face, this is referred to as picking.
The issue is more noticeable on the upper punch faces than on the lower ones. If tablets are repeatedly manufactured in this station of tooling, the problem worsens because more and more material is added to the already stuck material on the punch face.
Reason- Picking is especially dangerous when punch tips have engraving or embossing letters and the granular material has been improperly dried.
- Determine the best limit for drying the granules.
- Increase lubrication; polish with colloidal silica so that material does not cling to punch faces.
- Include materials with high melting points. Use lubricants with a high melting point.
- Refrigerate the granules as well as the entire tablet press.
- Compress at room temp.
- Reduce the amount of binder, switch to a different type, or use dry binders.
- Faces should be polished to a high lustre.
- Make the lettering as big as possible.
- To create a smooth and non-adherent face, plate the punch faces with chromium.
- Sharpness and depth should be reduced.
- Increase the pressure to the maximum.
Binding of Tablets
When the tablets adhere, seize, or tear in the die, this is referred to as binding in the die. A film forms in the die, preventing tablet ejection. Excessive binding cracks the tablet’s sides, causing it to crumble apart.
Binding is usually caused by an excessive amount of moisture in the granules, a lack of lubrication, and/or the use of worn dies.
- Dry the granules thoroughly.
- Increase the lubricant amount or use a more effective lubricant.
- Reduce the granular size, add more fines, and increase the lubricant quantity.
- Change the granulation. Granular size should be reduced.
- Reduce the size of the granules if they are coarse.
- Wear-resistant dies should be used.
- Lower the temperature.
- If it is extruding, increase the clearance.
- Polish the dies thoroughly.
- Investigate alternative steels or materials, or alter granulation.
- Resize to the proper size. Increase the space available.
- Reduce your stress. Alter granulation.
Mottling in Tablets
Mottling refers to an unequal distribution of colour on a tablet, with light or dark spots standing out in an otherwise uniform surface.
A coloured drug whose colour differs from the colour of excipients used in tablet granulation could be one cause of mottling.
- Make use of appropriate colourants.
- Change the solvent system, the binder, the drying temperature, and the particle size.
- To prevent segregation, mix thoroughly and reduce the size if necessary.
- During the powder blending step, incorporate dry colour additive, then fine powdered adhesives such as acacia and tragacanth, mix well, and finally add granulating liquid.
Double Impression in Tablets
Only punches with a monogram or other engraving are responsible for Double Impression.
The punch imprint is transferred to the tablet at the time of compression. On some machines, the lower punch drops and travels uncontrollably for a short distance before riding up the ejection cam to push the tablet out of the die. During this free travel, the punch rotates, and the punch may make a new impression on the bottom of the tablet, resulting in a Double Impression.
- Use keying in tooling, which means inserting a key alongside the punch to fit it and prevent punch rotation.
- Anti-turning devices on newer presses prevent punch rotation.