GUIDE TO INSPECTIONS OF LYOPHILIZATION OF PARENTERALSNote: This document is reference material for investigators and other FDA personnel. The document does not bind FDA, and does no confer any rights, privileges, benefits, or immunities for or on any person(s).INTRODUCTIONLyophilization or freeze drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. The process consists of three separate, unique, and interdependent processes; freezing, primary drying (sublimation), and secondary drying (desorption).The advantages of lyophilization include:Ease of processing a liquid, which simplifies aseptic handlingEnhanced stability of a dry powderRemoval of water without excessive heating of the productEnhanced product stability in a dry stateRapid and easy dissolution of reconstituted productDisadvantages of lyophilization include:Increased handling and processing timeNeed for sterile diluent upon reconstitutionCost and complexity of equipmentThe lyophilization process generally includes the following steps: Dissolving the drug and excipients in a suitable solvent, generally water for injection (WFI). Sterilizing the bulk solution by passing it through a 0.22 micron bacteria-retentive filter. Filling into individual sterile containers and partially stoppering the containers under aseptic conditions. Transporting the partially stoppered containers to the lyophilizer and loading into the chamber under aseptic conditions. Freezing the solution by placing the partially stoppered containers on cooled shelves in a freeze-drying chamber or pre-freezing in another chamber. Applying a vacuum to the chamber and heating the shelves in order to evaporate the water from the frozen state. Complete stoppering of the vials usually by hydraulic or screw rod stoppering mechanisms installed in the lyophilizers.There are many new parenteral products, including anti-infectives, biotechnology derived products, and in-vitro diagnostics which are manufactured as lyophilized products. Additionally, inspections have disclosed potency, sterility and stability problems associated with the manufacture and control of lyophilized products. In order to provide guidance and information to investigators, some industry procedures and deficiencies associated with lyophilized products are identified in this Inspection Guide.2 / 34It is recognized that there is complex technology associated with the manufacture and control of a lyophilized pharmaceutical dosage form. Some of the important aspects of these operations include: the formulation of solutions; filling of vials and validation of the filling operation; sterilization and engineering aspects of the lyophilizer; scale-up and validation of the lyophilization cycle; and testing of the end product. This discussion will address some of the problems associated with the manufacture and control of a lyophilized dosage form.PRODUCT TYPE/FORMULATIONProducts are manufactured in the lyophilized form due to their instability when in solution. Many of the antibiotics, such as some of the semi-synthetic penicillins, cephalosporins, and also some of the salts of erythromycin, doxycycline and chloramphenicol are made by the lyophilization process. Because they are antibiotics, low bioburden of these formulations would be expected at the time of batching. However, some of the other dosage forms that are lyophilized, such as hydrocortisone sodium succinate, methylprednisolone sodium succinate and many of the biotechnology derived products, have no antibacterial effect when in solution.For these types of products, bioburden should be minimal and the bioburden should be determined prior to sterilization of these bulk solutions prior to filling. Obviously, the batching or compounding of these bulk solutions should be controlled in order to prevent any potential increase in microbiological levels that may occur up to the time that the bulk solutions are filtered (sterilized). The concern with any microbiological level is the possible increase in endotoxins that may develop. Good practice for the compounding of lyophilized products would also include batching in a controlled environment and in sealed tanks, particularly if the solution is to be held for any length of time prior to sterilization.In some cases, manufacturers have performed bioburden testing on bulk solutions after prefiltration and prior to final filtration. While the testing of such solutions may be meaningful in determining the bioburden for sterilization, it does not provide any information regarding the potential formation or presence of endotoxins. While the testing of 0.1 ml samples by LAL methods of bulk solution for endotoxins is of value, testing of at least 100 ml size samples prior to prefiltration, particularly for the presence of gram。