The interval of use (manufacturing campaign) and the interval between end of use and cleaning are process parameters that
must be validated. Theoretically, the more batches a piece of equipment processes, the greater the soil load, and the more
difficult it is to clean. Hence, the need to challenge cleaning cycles after campaigns of different lengths. Nonetheless,
some products' physical, chemical, and surface adhesion properties do not change over the campaign length. For manufacturing
these products (dry processing), certain types of equipment do not allow residues to accumulate over time by design. This
equipment is sloped for gravity removal of product, whereby the soil load (both the amount and nature of the soil) after one
batch is comparable to the load after multiple batches within a campaign (i.e., "freely draining"). This can be verified by visual inspection on a routine basis. For stable products, manufactured in freely
draining equipment, there should be low-to-no process risks with respect to extending a validated campaign length based on
visual inspection. Routine inspections for visual cleanliness would mitigate any potential process risks with carryover of
process residuals and confirm cleaning performance. This same rationale could be applied to extending validated times for
the interval between the end of use and equipment cleaning.
Once a cleaning process is validated in a GMP manufacturing environment, the process should be monitored periodically to ensure
consistent and robust performance. Independent visual inspections should be incorporated into the periodic assessment program
to confirm that cleaning processes remain in a state of control. A second person should check for visual cleanliness, and
the frequency of recleaning is an appropriate metric for assessing cleaning performance. This additional control helps to
ensure robustness of the validated cleaning procedure. With an appropriate VRL program, visual inspection may be used rather
than surface and rinsate testing to demonstrate continued consistent cleaning performance.
Visible-residue limits (VRL) have been evaluated for pilot plants and manufacturing facilities from a risk-assessment perspective.
Opportunities for VRL implementation have been identified with the acceptable mitigation of the associated risks.
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