Establishment of acceptance criteria

The Cleaning Validation should demonstrate that the procedure consistently
removes residues of the substance previously manufactured down to levels that
are acceptable and that the cleaning procedure itself does not contribute
unacceptable levels of residual materials to the equipment. The limits set
should be practical, achievable and justifiable.
In Active Pharmaceutical Ingredient manufacture there may be partial reactants
and unwanted by-products which may not have been chemically identified.
Therefore, it may be necessary to focus on by-products as well as the principle
reactant. Companies should decide on which residue(s) to quantify based on
sound scientific rational.
Chemical determination
It is generally the residual Active Pharmaceutical Ingredient or intermediate,
which is of greatest concern rather than reaction side products or residual
impurities.
There are a number of options available when determining acceptance criteria.
Where either toxicological or therapeutic data if available then calculation A or
B is preferable. If data is not available for either of these calculations or if the
result is more stringent calculation C should be used.
A. Limiting the level based on toxicity data.
An Acceptable Daily Intake (ADI) is calculated with suitable safety
factors applied and this is converted to the maximum allowable
carryover to the API.
B. Pharmacological Dose Method:
The philosophy is to reduce the levels of residual product in each piece
of equipment, such that no greater than 1/1000 of the normal
therapeutic dose will be present per typical dose of the next product to
be run in the equipment. The validation protocol should include a
calculation, which ties this philosophy to the acceptance criteria for the
samples to be tested.
C. Limiting the level of product which could appear in the following
products.
Limits from 10ppm up to 0.1% (based on the ICH impurity document
which indicates that up to 0.1% of an individual unknown or 0.5% total
unknowns material may be present in the product being tested )
Note FDA Statement on 0.1% impurities
Guide to Cleaning Validation in API plants

FDA statement: P. Alcock, in Human Drug cGMP Notes, P. Motise,
June 98: „...we have found that some firms have incorrectly applied as
their acceptance limit the 0.1% impurity identification threshold as
discussed in both the ICH impurity guideline and the U.S.P. General
Notices. This application of the 0.1% impurity threshold is
inappropriate because the limit is intended for qualifying impurities that
are associated with the manufacturing process of related compound and
not extraneous impurities caused by cross contamination. ...“ ) may be
used depending on the stage of the process.
It is also necessary to evaluate the ability of the cleaning procedure to
remove any cleaning agents introduced. The acceptance criteria for the
residual-cleaning agents should reflect the absence of these materials,
within the range of the capabilities of the assay and sampling methods.
The individual company must decide on the Acceptance Criteria which
are justifiable for their particular situation.
Physical determination
There should be provision during routine cleaning for a visual examination of
the equipment, verifying that it is free of visible residues. The validation
protocol should include this requirement as an acceptance criteria. During
validation, special attention should be given to areas that are ‘hard to clean’
(e.g. agitator shafts, thermowells, discharge valves etc.) and areas that would
be difficult to verify on a routine basis.
Microbiological determination
Appropriate studies should be performed (e.g. swabs and/or rinse sampling)
where the possibility of microbial contamination of subsequent product is
deemed possible and presents a product quality risk.