Unique Aspects of Steam Sterilization Validation of Disposable Syringe Components

Abstract

Sterilization Validation of disposable syringe components presents unique process requirements due to component design and required mechanical attributes. These include the requirement of steam penetration through rubber plungers and closures since it is essential to sterilize isolated cavities formed between the rubber and syringe while minimizing thermal effects on the rubber components. Variations in process lethality relative to the sterilization cycle and component type have been observed and investigated. The investigations include determinations of steam penetration rates through various types of rubber closures which include natural, butyl and halobutyl rubber blends. Experimentation includes measurement of steam transmission rates for various rubber stocks and biological inoculations utilizing Bacillus stearothermophilus, ATCC #7953 spores. Differences in steam penetration rates observed between different rubber types and the effect on observed process lethality are discussed. Lag time considerations relative to classical F₀ calculations and associated errors are also presented. Methods used to determine rubber closure rheology and the mechanical attributes of the final syringe assembly are also presented. Critical process controls to assure a physically acceptable sterile syringe assembly are defined.