One of the common debates that arises from time to time where continuous cleaning verification is adopted that why do we need cleaning validation if we test after each product change?!
Cleaning validation refers to the process of providing a documented evidence that the cleaning process is capable of reducing the residue to safe limits effectively and consistently. Early US FDA guidelines on cleaning validation (e.g. guide to inspections validation of cleaning process in 1993) discouraged testing until clean practices where equipment are tested, resampled and retested until acceptable cleaning results are achieved. This was considered an indicator of cleaning ineffectiveness and that the cleaning method is not validated. Such practices were only allowed in rare cases (e.g. cleaning of clinical drugs where cleaning validation is not required) as the dependence on ineffective cleaning methods poses an unacceptable risk of cross contamination even with continuous cleaning verification (i.e. swabbing after each product change). Cleaning samples is an isolated time-point that was collected "hopefully" from the most difficult to clean spots of a piece of equipment. Considering that the swab to equipment surface area is significantly small ratio, it might not be a wise decision to rely solely on few sporadic cleaning swab results without considering the cleaning process design and the history of effective cleaning process that has been established through reproducible cleaning results of reasonably justified swab locations.
Only a well crafted cleaning validation study can provide this evidence of robust cleaning process where routine cleaning verification adds another layer of confidence in the validity of equipment cleaning. Moreover, the nature of equipment staining is usually not homogenous i.e. residues are not equally distributed on the surfaces which limits the value of swab sampling even if the most difficult to clean locations were selected as the residue can still exist in easy to access and clean spots if the cleaning method is badly designed (e.g. inefficient spray ball). In contrast, repeatable and acceptable cleaning results in a cleaning validation study can prove the effectiveness of the cleaning process (three successful runs). However, someone can argue that while swab samples are limited to significantly small surface area, rinse samples can represent most of the equipment surface, hence no need for the cleaning validation. Rinse samples are indirect sampling technique that require two elements to prove effective cleaning:
Recovery study so that the rinse solvent is able to recover the residues to acceptable percentage.
Ensure that the rinse solvent will contact all product contact surface area.
Both of the two conditions raises some challenges considering that as rinse sample lack the physical scrubbing effect provided by direct swabbing, usually rinses fail to recover the sticky residues and hence might not be the most accurate method to verify cleaning (depending on the nature of the expected residues). However, the confidence in the rinse results can be significantly improved in light of a successful cleaning validation study.
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