Process Capability and Six Sigma: A Necessity of Pharmaceutical Industry

The need of the day is to produce the product that meets customer requirements. As pharmaceuticals are related to health care this should be vital part of industry to produce a product such as tablets, capsules, ointments, creams, gels and emulsions etc. with minimum variation satisfying the needs of customer. Customer requirements are translated into ‘Critical to Quality’ (CTQ) characteristics of the products that they are about to produce by the formulation scientists.  As example, hardness, thickness, uniformity of weight, assay, dissolution etc are CTQ characteristics of tablets, Content uniformity, viscosity, density are CTQ characteristics of a gel etc.  There are various sources of variation which can be monitored by the Quality by Design i.e., QbD approach. Process should be monitored and controlled by using statistical process control which includes six sigma approach, process capability and control charts. Some of the more frequently used indices are Cp and Cpk. Cp represents process capability while Cpk is the process capability index which are determined between USL and LSL which signifies upper specification limit and lower specification limit. Cpk of at least 1.33 is desired, and 1.5 is excellent and if there are not more than 3.4 defects per million units, then six sigma is achieved.