Sterilization Methods

STERILIZATION METHODS

A sterilization process should always be considered a compromise between achieving good antimicrobial activity and maintaining product stability. It must, therefore, be validated against a suitable test organism and its efficacy continually monitored during use. Even so, a limit will exist as to the type and size of microbial challenge that can be handled by the process without significant loss of sterility assurance. Thus, sterilization must not be seen as a ‘catch-all’ or as an alternative to Good Manufacturing Practice but must be considered as only the final stage in a programme of microbiological control.

The European Pharmacopoeia recognizes five methods for the sterilization of pharmaceutical products:

1.      steam sterilization (heating in an autoclave);

2.      dry heat;

3.      ionizing radiation;

4.      gaseous sterilization; and

5.      filtration.

In addition, other approaches involving steam and formaldehyde and UV light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability requirements have generally served to limit this choice. Nevertheless, it should be remembered that even the recommended methods and regimens do not necessarily demonstrate equivalent biocidal potential, but simply offer alternative strategies for application to a wide variety of product types. Thus, each should be validated in their application to demonstrate that the minimum required level of sterility assurance can be achieved.

In the following sections, factors governing the successful use of these sterilizing methods will be covered and their application to pharmaceutical and medical products considered.