The greatest benefit of terminal sterilization is reducing the risk of a nonsterile product being released to the recipient of the product. Terminal sterilization, using any of the various methodologies (EtO, Radiation, Steam, Dry Heat), can be validated to provide a 10^-6 sterility assurance level (SAL) for the products sterilized using terminal sterilization methods. When terminal sterilization is used in conjunction with aseptic manufacture, the risk of a nonsterile is even further reduced. This can be accomplished two ways: 1) terminal sterilization of key components prior to aseptic manufacture and 2) terminal sterilization of the whole product after aseptic manufacture.

The new ANSI/AAMI/ISO 10993-7 should be published in 2009 and includes dramatic reductions in residuals resulting from the EtO sterilization process. Meeting the requirements of the new standard will depend on which EtO residual (EtO, EG, EC) is elevated in your product. EtO residual can only be reduced by 1) reducing the amount of gas to which the product is exposed, 2) reducing the amount of time the product is exposed to the gas, 3) adding air or nitrogen washes at the end of the cycle to remove the residuals, and 4) increasing aeration time and temperature after sterilization. If EtO residual is not extremely over the maximum allowed for the device, then typically nitrogen washes can be added at the end of the cycle to remove the excess residual, and additional aeration time is not required. If the product is porous or tends to hold EtO, then it may be necessary to change product components, develop a new cycle, or, in extreme circumstances, convert the product to radiation sterilization. In the case of EC residual, nothing in the EtO cycle will contribute greatly to reducing this residual. Typically what is causing elevated EC levels is the product’s exposure to chlorine or salt treatment prior to EtO sterilization, e.g., chlorine washing of textile products. If EC cannot be reduced to meet the new required levels of your product, then the manufacturer needs to examine either 1) pretreatment of the product with radiation prior to EtO sterilization instead of chlorine treatment or 2) removal of the processing step that is introducing the chlorine. The new standard or any standard associated with sterilization using EtO can be purchased at www.aami.org.

A number of factors affect the cost of sterilization, which make cost comparisons in general very difficult.

In a competitive environment, price and cost are not always related, but the following factors need to be defined before an answer can be given:

1.       Product characteristics.  Material type, product construction and presentation, and packaging.  All have an effect on the suitability of the sterilization method and the process cost.

2.       Dose required for irradiation and time and gas concentration for EtO.

3.       Volumes.  EtO is a batch process, and sterilizers come in many different sizes.  If the product provided does not fill the useable space, for whatever reason the cost per unit will rise.  Batch records cost the same for  1 pallet or 20 pallets!

4.       The sterilization company has very high capital investment in all systems, but how old and written down is the equipment?

5.       Do you include initial and on-going validation requirements?

The most effective sterilization process is one where the product has been designed from day one for one of the major sterilization methods.  Too often, sterilization is not considered until a product is in late stage development, thus making sterilization a “best fit.”

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