Validation & Training Programs

According to the 21 CFR 211.113 (b) ‘Appropriate written procedures, designed to prevent microbiological contamination of drug products purporting to be sterile, shall be established and followed.

Such procedures shall include validation of any sterilisation process’, it has clearly drawn a focus on the importance of sterilizing filtration system to be properly designed across all the bio-tech manufacturing processes.

In making the validation procedures of suitable sterilizing filters, it is best recommended to draft out a sterile filter master plan for the mentioned manufacturing processes. There are 8 major considerations for the validation engineers to evaluate before writing up the sterile filter master plan.

1. Appropriate to Use

The most important question to this consideration when choosing the sterilising filters used, will nonetheless be ‘what is the product to be filtered’ and ‘what processes will the product be going through’. The risk of contamination in the product & process conditions proportionately increases from upstream, downstream and eventually the final fill. This has given a good idea on the proper weightage of suitable and sizable filters should be placed in a validation plan. There is also a need for the sterilizing filters to be revalidated when if there are any process changes and product redesign.

2. Sterilization of the Filter

Before pushing the filters into the sterilization phase, it should be reasoned that the sterilization method is proven effective as this does not compromised the filter. Sterilizing filters can be sterilized in a certain of manners. Capsule filters can be gamma irradiated or autoclaved. Disk filter holders are autoclaved with the wetted filter in place. Cartridge filter installations are often sterilized by steam in place (SIP) operations.

The steam used should be free of particulate substance, such as rust and pipe scale that will be removed by the filter to be sterilized and shorten the filter lifespan. The validation of this step is rational if the filter is integrity tested following the mean of an actual filtration process.

3. Stability of the Filter Used

It is also important for the validation engineer to take note that the construct of the filter does not unfavourably affecting the product filtration process. Sometimes, the filter construct material can interact with the product, changing the conditions, such as temperature, pH, physical appearance etc. in the stream process.

This can commonly be validated by collecting data from the stream process conditions, then have them analysed using statistical means.

4. Binding on the Filter

Binding on the filter is basically referring to the study whereby the product-contact surfaces of a sterilizing filter does not bind to any formulation component causing product loss in the process. The filter should not remove active pharmaceutical ingredients, excipients, carriers, diluents, proteins, preservatives, or any other formulation component.

Binding and adsorption filter characteristics are measured in the qualification phase by using the adsorption analysis, to identify if the product content is partially retained in the filtration mechanism.

5. Compatibility of the Filter with the Process

Any conditions in the process, such as thermal, hydraulic, or chemical clash can be a major cause of adverse deformity in the structure of the sterilizing filter. The filter system must be qualified to demonstrate that all product-contact surfaces of the filter and its structural parts, including membrane support layers, core, cage, o-rings and other related components of the construct, can tolerate challenges of all the conditions of the sterilization and production processes.

Recently, there is an increasing demand for the testing of biocompatibility (biological safety) associated with the filters to be used in the pharmaceutical production, as part of the sterilized filtration validation.

6. Extractables/Leachables from the Filter

Extractables/ leachables testing is an important sterile filter validation as it identifies, quantifies and assesses the filter itself acting as a source of physical or chemical contaminants migrating to the process stream. Extractables are usually extracted from plastic or elastomeric materials in solvent under distressed conditions, while leachables refer to compounds that leach from plastic or elastomeric materials into the pharmaceutical product under normal conditions.

The nonvolatile residue test (NVR) is normally used to quantify the amount of such contaminants released by a filter into the process stream.

7. Bacterial Retention

A bacterial challenge test validates the ability of a filter to provide sterile effluent in any pharmaceutical product. Under controlled test conditions, the filter is challenged with a minimum of 107 viable B. diminuta (ATCC 19146) /cm2 of effective filtration area

This has been considered as most widely accepted approach for sterilizing filter validation because the bacterial challenge concurrently tests the physical-chemical interactions of the liquid product and the filter according to process conditions.

Validation of the bacterial challenge is usually performed by the filter company or an outsourced laboratory, using 47-mm disk filters to improvise a scaled-down volume of the pharmaceutical product required.

8. Integrity Testing

It has been well understood that the correlation between bacterial retention and a nondestructive integrity test, described in ASTM F838-05. Sterilizing filters for stream processes can integrity tested by the bubble point, forward flow or diffusional flow test or the pressure hold test, depending on the feasibility of each test to the applications.

Filter Manufacture Quality Assurance and Validation

The majority of sterilizing grade filters, as well as pre-filtration devices, are supplied into the highly regulated biopharmaceutical industry by outside vendors. This means that quality standards pertinent to the processes of the biopharmaceutical industry have to be applied to the vendors’ processes. These standards start with the qualification of the production equipment during the development phase, and extend through the validation of the production process in its entirety, definitions of in-process controls and documentation during the production process, release criteria, specifications and tolerance settings, and complete traceability of the finalized product and product components. Standard operating procedures and training matrices are as manifold within the vendors systems as with the equipment end-user.

Besides validating/qualifying the entire process, vendors are also asked to deliver qualification documentation that supports the process validation requirements of the filter user. Depending on the equipment, such qualification documentation can be elaborate due to the sub-components of the device.

Once the equipment is ordered or supplied to the end-user, most commonly the vendor will submit qualification documentation as described above, provide support for qualification and acceptance testing, and in some instances offer product- or process related validation services. The quality of the vendor’s production processes often mirror the production processes of the relevant industry of the vendor’s customer base. Additionally the vendors establish appropriate technical support structures to be able to react rapidly to any support needs of the industry. This is of importance as the end-user has to be able to answer regulatory enquiries or when equipment requires maintenance, calibration or repair. A production stand-still cannot be tolerated as it would resolve in multimillion dollar losses in revenue and put drug product batches at risk.


When finalized, the raw material quality, product parts production, assembly, and packaging specifications must be locked. This means that production parameters and tolerance are recognized and set, most commonly by repeated production batches as required within the industry itself. For example, machine setting, product formulations, production environments and flows have been defined and personnel trained accordingly. The locked-in parameters only create the assurance of reliable repeatability of the final product quality specification. The setting of production parameters also creates opportunities for analytical technologies to measure product specification during the production process. Process controls help to assure that the process is stable and performs as defined. When all specification, process requirements, and controls are defined, validation protocols and SOP have been instituted. Validation tests are commonly set by publicly available international standards, for example sterilizing grade filters have to meet current pharmacopeial requirements and will be tested accordingly. In the case of sterilizing grade filters, qualification tests are commonly performed, however these may vary from vendor to vendor:

  • USP Plastic Class VI
  • endotoxin
  • particulates
  • oxidizable substances
  • pH/conductivity
  • integrity test limits correlated to bacteria challenge tests
  • steam sterilizability
  • physical dimensions
  • operating parameters, like max. operating pressure/temperature
  • flow rate

Validation of the Filter and of the Filtration Process

The validation of sterilizing filtrations, and of the sterilizing filters involved is critical to the production of a sterile drug product, or of a sterile active pharmaceutical ingredient (API). The sterility of the drug preparation cannot be ascertained by analysis of its samples. It is impossible to test every drug container to assess its sterility. Similarly, a statistical determination of sterility would require so large a sampling as to be impractical. Validation of a process provides the assurance that its product is sterile. Such validation is a regulatory requirement (FDA, 1985). Validation of the filters used to achieve a sterile API is also necessary. It serves to assure that they perform in the manner intended; this may also be a regulatory requirement if there are no further sterilizing steps for the ingredient after its being formulated into the final product. Validation of a sterilizing filtration process used for pharmaceutical liquids essentially involves three things: determining the effect of the liquid on the filter, determining he effect of the filter on the liquid, and demonstrating that the filter removes all microorganisms from the liquid under actual processing conditions, resulting in a sterile filtrate (Madsen, 2006). One further point may need to be considered, namely, the interaction among the contaminating organisms, the solution, and the filter. Therefore, several studies are necessary to perform a complete filter validation. Such would include investigating extractables, chemical compatibility, initial filter performance, and bacterial retention testing. If the filter is to be post-use integrity tested in product-wet condition then validation of product-wet integrity test specifications is also necessary. Reuse testing is indicated if the intention is to use the filters more than once. This latter practice is not encouraged because of the heightened possibilities of cross-contamination.

Until rather recently it was believed that the sterilization of fluids could unerringly be achieved by their filtration through a “sterilizing” membrane whose proper and pertinent identity was confirmed by its pore size rating, which was itself determined by integrity testing. Developments in filtration practices showed this belief to be too generally founded. What had once seemed simple is now recognized as being quite complex. It was discovered that the positive conclusions based on pore size ratings were subject to modification by the physicochemical specificity of the organism-suspending fluid; by the individuality of the organism type in its size-changing response to the fluid; in the possible changes in pore size induced by the fluid’s effect on the filter; and by the adsorptive qualities of the filter resulting from its particular polymeric composition; all influenced by the filtration conditions in their numerous varieties, but especially by the transmembrane pressure. A filter may not sterilize the same preparation under different filtration conditions, especially under dissimilar differential pressures (Leahy and Sullivan, 1978). A given membrane may or may not retain a particular organism type suspended in a different drug vehicle (Bowman et al., 1967). The organism type need not remain constant in size, but may alter in response to its suspending fluid (Gould et al.,1993; Leo et al., 1997; Meltzer et al., 1998). The effect of the vehicle upon the polymeric membrane may cause a change in its pore sizes (Lukaszewicz and Meltzer, 1980). The certainty of obtaining sterile effluent requires far more than the identification of a “sterilizing filter” by a pore size rating. The complex of influences governing the outcome of an intended sterilizing filtration necessitates a careful validation of the process, including that of the filter (PDA Technical Report No. 26). The very drug preparation of interest, the exact membrane type, the precise filtration conditions, and the specific organism type(s) of concern should be employed in the necessary validation.

Given the complexity of the organism removal operation, it is doubtful whether a universal sterilizing filter can be devised. Certainly, there is no known absolute filter, one that will retain all organisms under all conditions, especially if viruses are included (Aranha, 2004). Therefore, the successful attainment of a sterile filtration with regard to specified organisms of interest must in every individual case be attested to by the documented experimental evidence that constitutes validation.

Training Programs :-

Filtration science and technology has made significant advances and is considerably more sophisticated and effective. However, many industry scientists and compliance personnel do not yet hold a thorough and necessary understanding of current filtration capabilities— and pitfalls. Our “Filtration & Validation” Training Program has been created to provide comprehensive, state-of-the-art information on all scientific and technological aspects of filtration. Filtration equipment in general has evolved considerably in recent years and some products used in last decade have become obsolete. One key development in the field is that most sterilizing-grade filters have at least doubled their total throughput and flow rates, accelerating filtration processes markedly.

In addition, the manufacturing regulatory environment has become more stringent and validation requirements have changed, increasing focus on the effectiveness of filtration methods and processes. Our training reflects these changes and covers the newest FDA and EMEA requirements.

As a result, the training on following subjects have been added to or expanded upon In Our “Filtration & Validation” Training Program :

  1. Prefiltration in Biopharmaceutical Processes
  2. Charge Modified Filter Media
  3. Filter Designs
  4. Pore Sizes and Distributions
  5. Concerning Mechanisms of Particle Removal by Filters
  6. Microbiological Considerations in the Selection and Validation of Filter Sterilization
  7. Filter Sizing: The Requirements and Their Attainment
  8. Filter Housings in the Biopharmaceutical Industry
  9. Stainless Steel Application and Fabrication in the Biotech Industry
  10. Protein Adsorption by Polymeric Filters
  11. The Filter Integrity Tests
  12. Filter Manufacture Quality Assurance and Validation
  13. Validation of the Filter and of the Filtration Process
  14. Extractables and Leachables Evaluations for Filters
  15. Endotoxin, Limulus Amebocyte Lysate, and Filter Applications
  16. Limulus Amebocyte Lysate Assays and Filter Applications
  17. Media and Buffer Filtration Implications
  18. Downstream Processing
  19. Crossflow Filtration
  20. Ensuring Safety of Biopharmaceuticals: Virus and Prion Safety Considerations
  21. A Rapid Method for Purifying Escherichia coli b-Galactosidase Using Gel-Filtration Chromatography
  22. Membrane Chromatography
  23. Expanded Polytetrafluoroethylene Membranes and Their Applications
  24. Air Filtration Applications in the Pharmaceutical Industry
  25. Sterility Testing by Filtration in the Pharmaceutical Industry
  26. Bacterial Biofilms in Pharmaceutical Water Systems
  27. Steam Sterilization of Filters
  28. Ozone Applications in Biotech and Pharmaceuticals