Medical freeze dryers inevitably experience shortcomings and defects during operation. As a key piece of equipment in the production process of sterile freeze-dried pharmaceutical preparations, and due to the special nature of pharmaceuticals, relevant departments have made clear regulations regarding the materials and performance of freeze dryers. So, what specific issues should be considered?
1. The Problem of Excessively High Vacuum Degree: During the freeze-drying process, the vacuum degree of the environment directly affects the length of the freeze-drying cycle. Too low a vacuum degree leads to a significant decrease in sublimation rate, while too high a vacuum degree, due to poor heat convection, will also significantly reduce the freeze-drying rate. Therefore, various methods must be adopted to control the pressure to achieve the optimal drying conditions required for the product. The main methods of pressure control include the diaphragm valve control method, the water vapor condenser control method, the small butterfly valve control method, and the gas entrainment method.
2. Lack of an independent gas filling device: After high-purity freeze-drying, a certain amount of drying, sterilizing, and inert gas is filled into the freeze dryer before stoppering. This protects the product and, more importantly, facilitates clinical use. High-purity filtered nitrogen is preferred for filling. Currently, some freeze dryers directly press the bottles under vacuum conditions. While this is beneficial for product protection, the extreme vacuum vibrating fluidized bed inside the bottles makes it difficult to remove the solvent after injection, causing significant difficulties for clinical use. Therefore, it is recommended to equip the freeze dryer with this device.
3. Improvement of the in-situ cleaning system: Some equipment, although equipped with in-situ cleaning nozzles, lacks a device to remove water vapor from the chamber. After each in-situ cleaning cycle, a lot of water remains on the plates and inside the freeze dryer, which must be wiped away manually. This process is prone to contamination, posing safety hazards to production. A well-developed in-situ cleaning system can not only shorten downtime and reduce labor costs but also maintain cleaning parameters. The cleaning effect and efficiency are not affected by the operator's individual work ability or attitude. The cleaning objective is easily achieved, with high reproducibility and reliability. Therefore, it is recommended to equip the system with a complete set of in-situ cleaning equipment and an in-situ sterilization system. Pure steam is preferred before in-situ sterilization. Compared with traditional chemical sterilization methods, this method eliminates the need for re-cleaning after sterilization, leaves no residue, avoids the possibility of secondary contamination, and does not corrode the chamber or other components. The sterilization effect is stable. A proven in situ sterilization system not only guarantees sterilization effectiveness but also has good reproducibility. Vaporized hydrogen peroxide or ozone disinfection can also be used, but the vaporized hydrogen peroxide sterilization system still needs further improvement.
