ABSTRACT
Filter membranes variously described as 0.2 or 0.22 mm by their manufacturers have been in routine use for about 30 years for the sterilization of pharmaceutical drug products.
Indeed, they are fundamental to the success of many aseptic production processes where
the final product cannot be rendered sterile by heat treatment (steam autoclave) or other
means. Equally critical to the success of any aseptic process where the sterilization of a
liquid pharmaceutical product is achieved by filtration is the ability to sterilize the filter
assembly. For disposable filter cartridges contained within rigid stainless steel filter
housings, this means sterilization using pressurized steam. In the early days of their use,
such filters were sterilized in a steam autoclave, after which treatment they were
connected to associated pieces of downstream equipment such as filling machine
components, using aseptic “sleight-of-hand” manipulations. As part of initiatives to
improve the safety and reliability of aseptic manufacturing processes, many of these
manipulations have been eliminated by the use of in-line steam sterilization procedures,
in which the assembled processing system is supplied with pressurized steam under
appropriate conditions to render the interior sterile.
