Low-Energy Electrons Have Pharma Beaming

J.W.: The commercial availability of small, low-energy electron beam systems for sterilization is relatively recent (<10 years). I consider it an “enabling technology” as it enables manufacturers to economically and reliably sterilize the surface of a product. I remember several years ago asking a pharma company director why his company implemented electron beam technology and he indicated that by using radiation he eliminated many of the concerns and questions associated with assuring the sterility of those items transferred into his filling isolator. Quite simply, he stated that every regulator understands terminal sterilization with radiation.

PhM: What are the most obvious applications of low-voltage electron beam technologies in the pharma industry? How broad are these applications?

J.W.: The most obvious is the most widely used application: the use of low-energy electron beams to sterilize the surfaces of tubs of syringes prior to introduction into a filling isolator. What comes next? The sterilization of individual containers (vials, syringes, or bags) in line directly in front of the filling equipment and low-energy sterilization of surfaces prior to connection are potential applications.

PhM: What are the advantages of EB for sterilization as opposed to UV, or chemical or thermal means? Any disadvantages?

Installing an electron beam emitter into process equipment. Courtesy of Advanced Electron Beam.

J.W.: With UV, shadowing is an issue. Chemical sterilization has issues with residuals and many materials cannot handle the temperature rise associated with thermal sterilization. Electron beam has the distinct advantage of speed and, in my opinion, ease of validation. Disadvantage: Like any form of ionizing radiation, electrons ionize oxygen, producing ozone that must be properly exhausted. The initial capital cost has been mentioned as a disadvantage but that is offset with its throughput capabilities.

PhM: Are there concerns about low-voltage electron beams and product degradation or alteration? What about its impact upon packaging materials?

J.W.: The great appeal of electrons is, by controlling their energy, you control how deeply they penetrate into the material. By using low-energy electrons, they only penetrate a few microns (<50 microns) into the material being treated so the material effects are negligible.

PhM: For sterilization applications, how fast is the process? How does this data compare to other methods of sterilization?

J.W.: The low-energy electron beam systems for the sterile transfer of materials into an isolator are designed to handle six tubs of syringes a minute continuously. This is substantially faster than sterilization of the outside of the tubs with hydrogen peroxide, which is typically a batch process. The amount of literature available on the effectiveness and speed of radiation sterilization is quite large and comprehensive.

PhM: What are the limitations of the technology that need to be overcome before it becomes more widespread?

J.W.: I am actually of the opinion that, based upon the sheer number of systems being used for the sterile transfer of syringe tubs, the use of electron beams in pharma is widespread. Education is one limitation. Providing educational opportunities so pharma can have a better understanding of potential radiation sterilization options would increase the use of low-energy electrons as well as the potential for terminal sterilization of drugs with radiation. ASTM is sponsoring an international dosimetry workshop next year in Germany (Karlsruhe, October 4-8, 2009) that has a special topics session devoted to low-energy electron beam dosimetry.  

About John A. Williams

John A. Williams is the Manager of the Corporate Sterility Assurance Research Center for Baxter Healthcare Corporation in Round Lake, IL. John has over twenty years of experience in the industrial applications of radiation for nondestructive testing, material modification, and sterilization.