STERILIZING GRADE FILTER &

FILTER VALIDATION

Ajeet Kumar Singh

STERILIZING GRADE FILTER

“ A filter which, when challenged with the

micro-organism Pseudomonas diminuta

at a minimum concentration of 107/cm2of

filter surface, will produce a sterile

effluent” ………… (1987)

“ A filter that, when appropriately

VALIDATED, will remove all micro-

organisms from a fluid stream,

producing a sterile effluent”

………..FDA(2004)

PARAMETERS

USP 28 FDABP2007 &

EC-GMP

Nominal pore size

Retentive membrane with a nominal pore size 0.2µm or 0.22µm

Retentive membrane with a nominal pore size 0.2µm or less

Bacteria retentive membrane with a nominal pore size of 0.22 mm or less

Pre-filtration Bioburden

NoPre-filtration is not recommended but setting of pre-filtration limit for bioburden is to be established

Yes. Pre-filtration bioburden limits – Not More Than 10 cfu/100 ml

Integrity testBefore useAfter use

YesYes

YesYes

YesYes

Cited Integrity test

Bubble pointPressure hold

YesYes

YesNo

YesYes

Microbial challenge test

A challenge of not less than 107

P.dimunata suspension per sq. com of filter surface area

A challenge concentration of at least 107 organisms per cm2 of effective filtration area of B. diminuta

A challenge of at least 107 cfu of P. diminuta per cm2 of active filter surface

STERILIZING GRADE FILTER REQUIREMENTS

PORE SIZE RATING

o 0.22 µm sterilizing filter membranes :

Capable of retaining 100% of a culture of

107 P.diminuta /cm2 of membrane surface

under a pressure of NLT 30 psi (2.0 bar).

………….USP-28

Use of Multiple Sterilizing GradeFilters in Aseptic Processes ……..

US PERSPECTIVE

o Use of redundant sterilizing filters should be

considered in many cases. This additional filter

must be satisfactorily tested before use, but

does not require post-use integrity testing

unless the primary filter fails……………PDA

Technical report

Use of Multiple Sterilizing GradeFilters in Aseptic Processes ……..

EU PERSPECTIVE

o Potential additional risks as compared with other

sterilization processes can do second filtration

(sterilized microorganism retaining filter)

immediately prior to filling.

o The final sterile filtration should be as close

as possible to the filling point.………(EU GMP)

Multiple filters US Vs EU

US EU

Filter #1 passes integrity

testing post-use, batch can be

released

Filter #2 is discarded without

testing

Filter #1 (Bioburden

reduction filter)

Must pass the post integrity

test

Filter #2 (Final Sterilizing

filter)

Must pass the post integrity

test

If filter #1 fails integrity

testing post-use, than filter

#2 is tested

If filter #2 passes, batch can

be released

FDA GUIDANCE NOTE

21 CFR 211.113(b) states that "Appropriate

written procedures, designed to prevent

microbiological contamination of drug products

relate to be sterile, shall be established and

followed. Such procedures shall include

validation of any sterilization process."

VALIDATION FO ASEPTIC

PROCESSING AND

STERILLIZATION

Parameter

Filter Manufacturer

Filter UserData Provided by

Millipore

Sterilization

Procedure

Recommend sterilizing

procedure with temperature and cycle time limits

Operate within the prescribed limits.

Validate the process

application

-

Integrity Testing

Provide filter usage limits

Validate for their process and

solution

Filter usage limits with water provided in the

guide. Product specific limit to be set by filter

user

FibresMeet non-fibre

release claim [21 CFR 210.(3b)]

Document the appearance of the

filtered product

Manufacturer certifies that the filter/cartridge is

non-fiber shedding

Sterilizing grade filter

Provide information on release criteria

Validate with their process solution

--

Requirements/Responsibility for Filter Validation

Parameter

Filter Manufacturer

Filter UserData Provided by Millipore

ExtractablesProvide extractables

data – type and amount, Pass USP test

Evaluate with their system and solution

Data provided with water. Done on model stream

systems

CompatibilityProvide compatibility

tablesEvaluate with their

solutionData provided for different solvents

Toxicity

Provide test data showing product meets

USP plastic test requirements

Document -

AdsorptionProvide known

information

Evaluate with their solution (both for active as well as preservatives)

-

Requirements/Responsibility for Filter Validation (contd….)

FILTER VALIDATION

o DEMONSTRATION OF BACTERIAL

RETENTION

o COMPATIBILITY STUDIES

o INTEGRITY TESTING

BACTERIAL RETENTION STUDY FOR STERILIZING GRADE FILTER

VIABILITY STUDY

Most appropriate method of delivering the challenge of

107/cm2Product viability study with B. Diminuta--------Direct Inoculation

Viability decrease greater than or equal to 1 log

Or

Oil based product

PRODUCT IS CONSIDERED ANTAGONIST

Surrogate fluid e.g. Saline lactose Broth ….for bacterial

retention

BACTERIAL RETENTION STUDY

PRODUCT CONDITIONING STAGEProduct is continuously filtered at desired flow rate for the max. processing time after that filter is rinsed to remove the product from the filter—Dead ended challenge filtration

CHALLENGED STAGEB. Diminuta is suspended in product/media and Product is continuously filtered at desired flow rate for the max. processing time

Analysis of filtrate for the the presence of B.diminuta

BACTERIAL RETENTION STUDY (contd…)

ACCEPTANCE CRITERIA

o 0.22µm filter must demonstrate complete retention. o 0.45µm filter (Positive control) must demonstrate

complete recovery of test organism.

o Sterility of the test system shall be demonstrated

o 0.22 & 0.45µm filter must not fail in the post integrity test.

COMPATIBILITY ASSESSMENT

Chemical and Physical resistance

Filter is subjected to:

o Microscopic inspection for the absence of

damage which might influence the filter

performance

o Dimensional measurements

o Extractable and Leachable analysis

STRUCTURAL COMPATIBILITY

SWELLING OF FILTER

Pore space tighterFlow rate decrease

Bubble point ( )

PLASTICIZING EFFECT

Release the polymer stress

Pore space openFlow rate increaseBubble point ( )

o To ensure the structural compatibility recording

of Bubble point is necessary after contact with

the product

ADSORPTION

o Formulations containing low

concentration of actives

o Product containing preservatives

o Specific nature of actives ingredients

INTEGRITY TESTINGObjective: To ascertain whether changes in the filter

may have occurred during filtration

Conform the correctness of the filter manufacturer’s

pore-size rating

If fails in the final integrity test ------filtrate should be

re-filter or discarded

Laplace law

P: Pressure necessary to expel the water

D: Diameter : Surface tension

: Angle of wetting

P =4 Cos

D

Bubble Point

o Liquid is held in the pores of the filter by

surface tension and capillary forces.

o The minimum pressure required to force

liquid out of the the pores………..Bubble

point

o Bubble point is a function of wetting liquid

surface tension, pore size Specific to

membrane polymer

Filter wetted with Purified water(approx. 200 ml (Temp.---, Time 15-20 mins)

Record the bubble point

Repeat the test with rewetting the membrane until stable bubble point in three consecutive

tests

Repeat the test with test fluid

Calculate the Bubble point ratio (BPR)

Procedure for Bubble point determination

Manually determination of Bubble point

Bubble Point

If Bubble point value lower than the

specification:

o Non-integral membrane

o High temperature

o Integral filter,but wrong pore size

o Incomplete wetted membrane

Diffusive flow/Forward flow test

o Pressure at which gas molecules that migrate

from water-filled pores of a wetted

membrane.

o Directly proportional to the differential

pressure and the total surface area of the

filter.

o Filter Wetted with liquid Upstream side of

the filter pressurized diffusive flow is

measured

Pressure Hold/ Decay Test

o Indirect method diffusive low/forward flow

testing

o Filter housing pressurized Gas flow across the

membrane quantitatively measured as decay in

the pressure over a specified period of time

o Conform the integrity of the entire filter

assembly

o Pressure decay below the max. allowable value

Passes the physical integrity test

Test Sample Size

Bubble Point200 ml from three

different lot

Viability study50 ml from one lot

(Sterile)

Bacterial retention study & Compatibility

2000 mL from one single lot

Filter validation sample requirements

DRF MFG. SITE

Establish lead formula based on Pre-formulation

Studies

Compatibility

Adsorption

Integrity Testing (200 ml

non-sterile

sample of 3 lots)

Batch Size, Operating Conditions

•FILTER MFR.Extractables – Model Solvents

Bacterial Retention

50 ml sterile sample for viability testing

2000 ml

MAPPING OF ACTIVITY

Product Description

o Aq/Non aq.o Biological/Non Biologicalo pHo Specificity Gravityo Viscosityo Detail unit formula along with CAS

No.o MSDSo Neutralizing agento Sensitivity if anyo pH modification possibleo Product description (Preservative)

INFORMATION NECESSARY FOR ACCESS QUESTIONNAIRE

Critical Process Description

o Processing Temp. for Filtrationo Minimum Batch Size (Min, Actual

and max.)o Filtration (Continuous/Intermittent)o Flow Rate (mL/min)

Test gas o Compressed Air / Nitrogen/Other

Type o Membrane/Cartridge

Process type o Continous / intermittent

INFORMATION NECESSARY FOR ACCESS QUESTIONNAIRE

Contd...

Ensure that the following information is

available on the filter

o Compatibility

o Bacterial Challenge Testing

o Extractable Testing

o Product Specific Integrity Testing Values

CONCLUSION