In the past, glass was considered as completly inert primary packaging material. The situation has changed since it has been discovered that many reactions may occur on the inner surface of some glass containers. In the last two years, the growing problem of glass particles in injectable medications (like syringes or ampoules) has led to a number of product recalls. This has now become the focus of public attention. Glass and product quality as well as external factors may cause the shedding of glass fragments - a phenomenon also called delamination. In March 2011 already, the FDA drew attention to this issue in a document entitled "Advisory to Drug Manufacturers: Formation of Glass Lamellae in Certain Injectable Drugs". The following risk factors have been associated with a higher incidence of delamination: glass vials manufactured by higher temperatures (tubing process), drugs formulated at high pH and terminal sterilization. Yet, type I glass is not equal in terms of quality.
Usually, glass containers must comply with the requirements of USP Chapter <660>. Although the tests provides an indication of the durability of the surface, it does not provide a direct correlation with the susceptibility to form glass particles or to delaminate. The interaction between the product itself and the container is not addressed in the chapter. Therefore, the tests presented in Chapter <660> represent only the first step in quality control. Additional tests should be employed.
The new USP Chapter should provide approaches to help predicting the potential for disintegration to occur like for example:
- Good Glass Supply-Chain Practices: recommendation when selecting a glass manufacturer, audit of the manufacturer, determination of whether the containers have been treated with ammonium sulfate, etc.
- Glass surface chemistry: discussions about chemical methods and treatment steps to increase glass stability.
- Factors that influence inner surface durability: this chapter presents elements which may influence the stability of the inner glass surface like for example certains conditions under which the containers were manufactured or characteristics of the subsequent filled product.
You can find more information about the topic in a USP briefing entitled: "<1660> Evaluation of the Inner Surface Durability of Glass Containers".
Dr Robert Eicher
CONCEPT HEIDELBERG (a service provider entrusted by the ECA Foundation)
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