How a package fails doesn't necessarily correlate with its shelf life. That was the underlying message of a presentation by Douglas Stockdale.

Stockdale noted that accelerated-aging tests only confirm real-time aging data and that it's impossible to plan in the lab for everything that may occur in the real world. “Companies should continue to monitor their products years after the products are on the market and exposed to various environments,” he said. He also emphasized that documentation is often the only proof of testing. Stockdale is president of Stockdale Associates Inc. (Rancho Santa Margarita, CA).

Accelerated-aging testing is an element that illustrates the importance of consistency when defining test parameters as they relate to ISO 11607, “Packaging for Terminally Sterilized Medical Devices.”

Stockdale explained how to identify and set testing parameters to achieve thorough and cost-effective results. Above all, he stressed the need to be consistent.

“A design configuration should describe what you will accomplish in achieving qualification,” said Stockdale. “It should define protective packaging configurations in your packaging system.”

Packages—from the primary blister package, to the secondary carton, and finally to the tertiary case, for example—need adequate protection throughout distribution; so environmental extremes need to be defined before testing. Stockdale stressed the need to “be consistent throughout the packaging system in how one defines those extremes to prevent adding unnecessary layers of protection, which in turn means added costs.”

Stockdale emphasized the benefits of using standard test methods. Standard methods are, in a sense, “prevalidated.” Using modified or custom test methods requires further validations, which also require extra time and money.

Stockdale also mentioned that medical devices with the same packaging systems can be grouped for validation, a practice recognized by FDA. Using statistical analysis in packaging validation, such as using confidence intervals for sterilization, he said, also requires defining acceptance criteria, similar to defining environmental extremes. Acceptance criteria are defined relative to individual firms. “A company's minimum seal strength, for example, should be based on that company's own product-usage requirements,” Stockdale said.

Accelerated-aging testing is critical to understanding potential package weaknesses and knowing how to address product damage problems that can occur even years after the product has passed its accelerated-aging tests and has been put on the market.

Again, Stockdale stressed the need to be consistent when following testing guides, such as ASTM F1980, “Standard Guide for Accelerated Aging of Sterile Medical Device Packages.”

“Be consistent throughout the distribution chain, and understand your own system,” he said. “When using ASTM F1980, use 23°C for the ambient temperature in a warehouse or 25°C for a noncontrolled-temperature warehouse, but remember to factor in the location and any effect it may have on warehouse temperature.”

Stockdale also suggested taking a long-term, strategic approach to real-world monitoring by identifying material combinations and supervising their performance after sterilization and aging.

Particularly important, he said, is that no matter how you define your test parameters, test your packages, or validate your products and procedures, the ultimate rule is that “if it's not documented, it never happened.” Documentation not only proves a company has done its best to ensure the integrity of its product, but it also serves as a record on which to improve in the future.

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