It is instructive to review the various techniques for sterilizing components used in parenteral drug packaging. These methods can be divided into physical and chemical processes.
1. Heat
Steam sterilization is a common and accepted method for many parenteral drug components and has no measurable effects on a rubber compound’s physical or chemical properties. However, because steam often results in residual moisture, subsequent drying steps are required that may affect rubber properties. Steam’s residual moisture also makes it a less desirable sterilization choice for certain drug products which are reactive to any moisture.
2. Irradiation
An alternative physical technique, Gamma irradiation, offers higher penetrability through electromagnetic wave properties, making it more suitable for dense bulk sterilization, even for full pallet configurations. This is a popular option for manufacturers because it is considered reliable and cost-effective. It is also clean, leaves no residuals and operates at low temperatures. While the chemical properties of elastomers are not altered by gamma irradiation, there could nevertheless be alterations in the physical properties of the rubber.
3. Chemical
EtO sterilization is widely used in the biopharmaceutical industry; its effectiveness, however, depends on variables such as pressure, time, gas concentrations, temperature, and relative humidity, requiring careful monitoring.
Because rubber typically absorbs EtO residues, sterilization should only take place with dedicated rubbers that have high EtO permeability. Importantly, EtO is not suitable for certain compounds like butyl rubber because of chemical byproducts that are created. EtO has also received some unwanted scrutiny from the EPA over environmental concerns.