Michael Gamlen and Dipankar Dey at Gamlen Tableting Limited
Poor lubrication results in picking and sticking problems during production. These are one of the most common causes of tablet defects which result in slow running of the tablet press and reduced output. High ejection stress (>5 MPa) is strongly correlated with manufacturing problems.
The effect of lubricant concentration on tabletability, tablet ejection and detachment can be evaluated using the Gamlen D series. Lubricant effectiveness rank order varies between materials; some materials are better lubricated by sodium stearyl fumarate than by magnesium stearate.
Detachment (take-off) force and peak ejection force should be evaluated as potential critical quality attribute for tablets.
Successful implementation of the principles of Quality by Design relies upon the capability to make accurate and reliable measurements of material properties. The critical quality attributes (CQAs) relating to tablet compression are tabletability, compressibility and compactibility. The CQAs relating to tablet lubrication are the ejection profile (peak ejection force and ejection force vs displacement profile), and the punch detachment, or take-off, force (force required to detach the tablet from the punch). In principle these should be optimised on a product by product basis.
Ejection studies on instrumented tablet machines are normally difficult to perform because the same load cell is used for measuring compression force as is used for ejection, but ejection forces are much smaller and so hard to measure accurately. Measurement of detachment, or punch take-off force is not normally undertaken at all during laboratory evaluation.
The purpose of this work was to study the impact of blending time and lubricant concentration on ejection and detachment as a trial for QbD lubrication studies.
Materials and methods
Galen IQ720®, Pearlitol 500DC®, magnesium stearate (MS) and sodium stearyl fumarate (SSF, PRUV®) were used as received. Batches of 100g excipient were blended with 0.5 and 1% of each lubricant for 5min a Turbula blender. Tablets were compressed using the Gamlen D series, t forces between 100 and 500kg using a 5mm punch and die and 70mg nominal tablet weight. Compaction and ejection forces, and punch displacement, are recorded by the machine automatically and exported to
Excel for data analysis. The tablet detachment (take-off) force was recorded using a manually operated 500N McMesin CFG+ force transducer. Tablets were fractured at a speed of 1mm/min.
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