Changing radiation sterilization modalities can be challenging with medical devices that have a narrow  dose range. Particularly, a change from Gamma to E-beam can be challenging because the e-beam process may increase dose uniformity ratio (DUR) depending on the loading configuration used. Developing a process that allows for product to be sterilized more than once is not common for radiation due to the material effects on sensitive polymers. To optimize processing, considerations must be made early in the product development and sterilization validation life cycle such as sterilization dose, maximum acceptable dose (MAD), and alternative dose mapping configurations.

In practice, to achieve two times sterilization processing capability, the combined total maximum absorbed dose to product from the 1st and 2nd sterilization process should be below the established MAD of the product.  Typically, a 2x process would consider doubling the max dose delivered to the product from the 1x process (e.g a 1x dose range of 25 – 50 would have a max dose of 100 kGy and require an established MAD of 100 kGy). For sensitive polymers, a MAD of 100 kGy may not be possible. The evaluation of alternate product configurations and lower sterilization dose may solve this problem.

A dose ranging study to assess product performance impact of polytetrafluoroethylene (PTFE) across 30 – 90 kGy is reported (see Figure 1) to evaluate if a product can be re-sterilized based on a current validated dose range of 25 – 50 kGy.  The outcome showed that the traditional 25 – 50 kGy processing range did not allow for a 2x process, however lowering the sterilization dose to 20 kGy and increasing MAD to 65 kGy allowed for the opportunity for processing a 2nd time with an alternate loading configuration (low DUR).