“Understanding and Overcoming Picking and Sticking in Tablet Compression”

Tablet defects:  Sticking and picking are the two most prevalent issues observed during tablet compression, most of you may not differentiate between them due to the similarity, as both defects involve materials adhering to the parts of the compression machine. After reading this article you will be able to differentiate between sticking and picking and also will be aware of the reasons for both these problems.

What is Tablet Sticking?

Adhering granules or powder to the punch tip surface or the die walls of the compression is considered sticking, and this will affect the quality of the produced tablets.

What is Tablet Picking?

During compression process after the formation of tablet, when the upper punch retracts from the die space, some material gets adhered to the punch tip especially when there is a embossed or debossed letters are present on the punch tip. This results in removal of some material from the tablet, leaving visible imperfections on the tablets surface.

Reasons for Sticking and Picking

1. Formulation-Related Causes

The first cause for sticking and picking lies in the formulation, theformulation related problems include  

• High levels of moisture present in the granules mostly due to insufficient drying at wet granulation step.
• Uneven drying can lead to sticking and picking
• improper ration of fines in formulation can increase the problems of sticking
• If the materials used in the formulation are hygroscopic, this results in sticking and picking
• Inadequate lubrication also causes sticking and picking.

2. Machine-Related Causes

The condition of the tablet press machinery is another critical factor:

• Condition of Punches and Dies: Worn or damaged punches and dies can lead to uneven compression, increasing the risk of sticking and picking.

3. Environment-Related Causes

Environmental factors such as temperature and relative humidity (RH) can influence sticking and picking:

• High RH levels result in absorption of moisture by granules, leading to sticking.
• Extreme temperatures can affect the stability of the formulation, increasing the possibility of sticking and picking.

Measures to Prevent Sticking and Picking

To mitigate sticking and picking, it is essential to:

• Care should be taken during drying, so that granules maintain optimal moisture levels, as more moisture can results in sticking and picking and environmental conditions must be controlled
• Improve the lubrication
• Use anti adherents
• Use punches with special coatings
• Regulate the temperature
• Enhance the operator skill