During an optimization process for a 5 mg tablet formulation (let's call it "Z"), a formulator encountered significant issues during compression specifically, capping and low hardness. The maximum tablet hardness reached was only 2 kP, far below the minimum requirement of 6 kP, as confirmed by previous stability studies.
The puzzling part? The formulation and materials used were identical to those in the stability batches, where no such issues occurred.
After deep analysis and brainstorming, the culprit was identified: the magnesium stearate (Mg-stearate). In the stability batch, Mg-stearate with a surface area of 7 m²/g was used, whereas in the current batch, Mg-stearate with a surface area of 23 m²/g was applied.
This subtle difference significantly affected the tablet's compression properties and highlights how even small variations in excipients can have a substantial impact on product performance.
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