New report reveals PROSOLV® EASYtab to be exceptional material with large capacity for dilution and excellent compaction characteristics

Report by Dr Michael Gamlen


The objective of this work was to establish the effect of adding a range of concentrations of ascorbic acid to PROSOLV® EASYtab, a multi-functional tableting excipient. The work was done using the Gamlen D series powder compaction analyser and included a wide range of key compression parameters. EASYtab was found to be an exceptional material with a large capacity for dilution; even material containing 40% ascorbic acid had excellent compaction characteristics.









Introduction to assessment of lubricity and compressibility


Introduction Determining whether a powder will form a good tablet is a complex process because for a material to make a good tablet it requires a number of different attributes which in some ways conflict with each other. For example, it needs to be well lubricated but also to be easily penetrated by fluid in the gut.  It also needs to be physically robust but also break down rapidly in the body. The parameters we have identified which determine manufacturability are set out below.
The most important requirements are for it to be readily compressible, well lubricated, and to exhibit acceptable recovery (as excessive elastic recovery has been associated with manufacturing defects such as capping.
Parameter What is it? Why does it matter?
Tabletability Tabletability is the relationship between tablet mechanical strength and the  pressure used to make the tablet Tabletability is maximised to ensure that the porosity of the tablet is as high as possible for any given compaction presure.  This maximises liquid penetration into the tablet, and therefore tablet dissolution rate.
Ejection stress Ejection stress is the stress generated during the tablet

ejection process.  It is a measure of how well lubricated the tablet is; reducing ejection stress is the purpose of adding lubricant to the formulation

Poor lubrication results in picking and sticking problem during production.  This is one of the most common causes of tablet defects which results in slow running of the tablet press and reduced output.  High ejection stress (>5 MPa) is strongly correlated with manufacturing problems.


A force is needed to detach a tablet from the punch tip during manufacture.  Detachment and ejection stresses are related for some products, but unrelated for others.  If detachment stress is too high, defects such as picking and sticking are seen.  These can be reduced by punch material selection. We are also concerned about formulations in which detachment stress is substantially higher than ejection stress as this shows unusual interaction between the material and the punch tip.
Elastic recovery Some materials change tablet thickness between being compressed and being ejected.  In some cases contraction of the tablet is seen while in others, and more commonly, expansion occurs. Elastic recovery is widely held to be one of the causes of capping, a major tableting defect which requires slowing of the tablet press for resolution, sometimes with a massive impact on productivity.  Checking for elastic recovery during development and manufacture is therefore important
Risk of overcompaction Solid fraction is a measure of the porosity remaining in the tablet.  It is calculated from the weight and dimensions of the tablet, and the absolute density of the components. The recommended maximum solid fraction for a tablet is 0.85, although many products exceed this.  Products with very high solid fraction are prone to capping and dissolution problems. Over-compaction is a serious tableting problem.

Download full report: Analysis of PROSOLV® EASYtab with added Ascorbic Acid
(Scroll down document list to date of post: 25 May 2017)

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