An evaluation of the relative importance of formulation and process variables using factorial design

A factorial design method for assessing the relative importance of various formulation and process factors and their interactions in model paracetamol tablets is described. The design was a 2 X 2 X 2 X 3 type using mixing time, starch concentration, drug particle size and compaction pressure respectively. The starch concentration was the most significant factor in affecting the dissolution rate but the larger drug particle size also gave a significant increase in drug release rate. Interactions between starch concentration and drug size and between these and mixing time were also observed. The most significant factor affecting the tensile fracture stress of the tablets was the mixing time, followed in order by the drug particle size, starch concentration and compaction pressure.