Freeze drying is a technique to remove water. The dry product is much more stable than a solution. The reduced weight and volume is a big advantage and the removal of the water does not change the activity of the product. This technique involves freezing the product on a shelf using typically –40 to –80°C, applying a vacuum and then slowly heating the product to ensure the ice turns into vapor. This removes the water content from product by a process called sublimation.
The critical parameters during freeze-drying are temperature (product and shelf) and pressure/Vacuum. These measurements are usually recorded with every cycle to determine when the product is dry. In addition to monitoring each cycle, freeze driers also require regular validation.
By removing the water from the material and sealing the material in a vial, the material can be easily stored, shipped, and later reconstituted to its original form for injection.