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There is no controversy over the need for cleaning validation for any lyophilizer that will be used in the manufacture of an aseptic sterile drug, sterile device, or sterile in vitro diagnostic.   In the 1993 Guide to Inspection of Lyophilization of Parenterals, we don’t find a directive to perform cleaning validation, but we see

It is a good practice as part of the validation of cleaning of the lyophilization chamber to sample the surfaces both before and after cleaning.

The above statement is in a part of the website titled Inspections, Compliance, Enforcement, and Criminal Investigations.

Further documentation of a requirement to clean and to validate that cleaning can be found at the FDA site under the title Guide to Inspections Validation of Cleaning Processes.  The requirements are spelled out and leave no room for misunderstanding.

How to Clean

Having established a requirement for cleaning a lyophilizer used to manufacture sterile regulated products, we next address how to do it.   Previously, FDA has approved products that were manufactured in lyophilizers not fitted with CIP (“clean in place”) and that for all practical purposes could not be cleaned due to the lack of accessibility.   While such approvals may be in place and viable, it is highly doubtful that any new approval would be granted for a non-CIP Lyophilizer used to manufacture aseptic drugs, devices, or diagnostics.   The only conceivable exception might be to a small, hand cleanable machine that was used solely for one product.

A CIP system for a lyophilizer is usually designed and installed by the lyo manufacturer.  During the commissioning phase, tubing and nozzles are adjusted to provide complete coverage. Since every unit is essentially a one-off, that coverage should be confirmed by the customer during FAT (factory acceptance testing).   Typically, it should be shown that the water cycle is sufficient to remove 0.1% riboflavin solution that has been painted onto the surfaces and dried at by heating the lyophilizer to 50°C.   Most likely, hot water (82°C) will be needed to remove the fluoresence.

To validate the removal of a specific product (other than detergent), calculate the Maximum Allowable Carryover (MAC) for the product and show that the cleaning method reduces a spiked amount to less than the MAC.   Detergents should always be cleaned to “non-detectable” as demonstrated by the most sensitive analytical method available.

Another cleaning limit that is sometimes used for lyophilizers is called “clean to background level”.  To do this, the firm must establish a total organic carbon (TOC) background for swab and/or rinse samples with a statistically acceptible sampling method.   The surface is then subjected to a routine cleaning, following a challenge contamination, and using a test for total organic carbon, the sample is shown to be returned the background TOC level.

Water Quality Used for Cleaning

The CIP system must not provide contamination to the lyophlizer!  One can use a detergent with CIP to clean the lyophlizer, but as a rule, it is unusual that the parts being cleaned would have contacted any significant amount of product.   The known exception is when product vials break and deposit their contents within the unit.   FDA is correct in assuming that such events take place.   Still, most lyophilizer cleaning is done with de-ionized water followed by a WFI rinse. Many producers find it more convenient to use WFI only, since a single tank is all that is required.

De-ionized, de-mineralized, or Purified Water, USP is not typically acceptable for the final rinse of a lyophilizer.   Although the interior walls and shelves are not what one would typically call a “product contact” surface, there is an argument that product or micro-organisms from one freeze-drying event, or from the cleaning water source, could be deposited on the lyophilizer surface and find its way into a vial, or, in the event of a tray drying procedure, then directly onto the product.  As a consequence, the industry standard (the c in cGMP) is to use WFI as the CIP cleaning liquid and to refer to the lyophilizer surfaces as “product contact”.   This has been the case since at least about 2004 with the publication of Guidance for Industry Sterile Drug Products Produced by Aseptic Processing — Current Good Manufacturing Practice.

Steam Sterilization

That an aseptic lyophilizer would have to be sterilized should be obvious.   The most common method for sterilization is steam.   Steam quality should be the same as that required for a sterilizer since the chambers are very similar.   When steam first enters the cold chamber, large quantities of it condense into water.   If Pure Steam, USP is used, then that water is WFI and there is no question about contamination.   Otherwise, the condensed steam must be validated to show that it can never be a source of contamination.  Also, if steam were to be used from a source that permitted mist to be carried into the lyophilizer, then sterility validation might be compromised since the tiny droplets of water (mist) were never converted into the gas phase and thus could carry over non-volatile organics and endotoxins.

The sterilization process must be validated.  In the case of steam sterilization of an empty chamber, the validation is straight-forward.   Using Pure Steam, USP, the cahmber is exposed to 121°C for 30 minutes and shown to have a 12 log reduction of Bacillus stearothermophilus spores.