Sterilization Control and Sterility

STERILIZATION  CONTROL  AND  STERILITY

To be labelled ‘sterile’, a product must be free of viable microorganisms. To achieve this, the product, or its ingredients, must undergo a sterilization process of sufficient microbiocidal capacity to ensure a minimum level of sterility assurance. It is essential that the required conditions for sterilization be achieved and maintained through every operation of the sterilizer. Some examples of typical conditions employed in sterilization are shown in Table 21.5.

Historically, the quality control of sterile products consisted largely, or in some cases, even exclusively, of a sterility test, to which the product was subjected at the end of the manufacturing process. However, a growing awareness of the limitations of sterility tests in terms of their ability to detect low concentrations of microorganisms has resulted in a shift in emphasis from a crucial dependence on end-testing to a situation in which the conferment of the status ‘sterile’ results from the attainment of satisfactory quality standards throughout the whole manufacturing process. In other words, the quality is ‘assured’ by a combination of process monitoring and performance criteria; these may be considered under four headings:

•              Bioburden determinations

•              Environmental monitoring

•              Validation and in-process monitoring of sterilization procedures

•              Sterility testing.

In well-understood and well-characterized sterilization processes (e.g. heat and irradiation), where physical measurements may be accurately made, sterility can be assured by ensuring that the manufacturing process as a whole conforms to the established protocols for the first three of the above headings. In this case the process has satisfied the required parameters thereby permitting parametric release (i.e. release based on process data) of the product without recourse to a sterility test.