Drugs and the pharmaceutical sciences

Foreword
Filtration has been used successfully for microbiological control in water and
pharmaceutical manufacture for many years. However, much of the knowledge that
was the basis of its use was empirical and incomplete. For many, the idea of filtration was
the sieve concept, and the use of terms like “pore size” encouraged that thinking. As a
result of this incomplete knowledge, some notable instances of unsuccessful filtration
have occurred.
There exists competing pressures for filter selection in the biopharmaceutical
industry. In the simplest sense, there is the need to sterilize the solution, which calls for
smaller pore size ratings, while conversely there is a need to put the solution through the
membrane in a reasonable amount of time, which calls for greater pore size ratings.
Understanding the myriad of additional options is a significant challenge that will
improve filtration processes.
Understanding the mechanisms of filtration and proper applications of the
technique has been the quest of many industrial scientists. The transition from intuitive
opinions to scientific conclusions based on physical and biological measurement has
permitted a reassessment of our understanding of the mechanisms of filtration. Frances
Bowman’s early studies probably ignited much of the inquiry relating to this undertaking.
However, the technology has remained dynamic, as evidenced by the introduction of new
membrane materials, innovative equipment, and new methods to examine filtration. In
this revision of the Filtration series, up-to-date information is presented on a broad range
of issues surrounding biopharmaceutical applications. These topics will assist the reader
in developing well-controlled manufacturing processes and preparing quality products.
David Hussong, Ph.D.
Associate for New Drug Microbiology
Office of Pharmaceutical Science
Center for Drug Evaluation and Research
U.S. Food and Drug Administration,
Beltsville, Maryland, U.S.A.
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