Sticking and picking is a common tableting problem, occurring when particles of the tablet formulation adhere to the punch face and disrupt the integrity of the tablet surface.  The sticking tendency of a new formulation has traditionally been difficult to predict during development due to short production runs and limited press data.  The consequences in production can be disastrous if encountered too late for reformulation. The presentation will be describing ways in which sticking has been investigated in the past using compaction simulators.

The development of an instrumented adhesion punch (Fig.1) allows the generation of quantitative data to be generated on very small samples in the laboratory.  The punch measures the force required to remove the punch tip from the surface of the compact. Data for ejection force and take off force can give a broad picture of the sticking behaviour of materials.  The results are used to calculate the Picking Index:

The picking index can be used to assess the risk of adhesion with development formulations. This gives the potential to quantify sticking risk and discover issues early enough in development to find a solution.