Freeze Drying Process Development and Process Transfer
Freeze drying cycle performance in the laboratory can be much different from a cycle in manufacturing scale freeze drying, even when using identical process conditions. The present procedure of qualification of a freeze dryer may not provide sufficient information about the overall performance of the machine which is, in turn, a drawback when recipes must be transferred from one dryer to an other one. Variation of shelf temperature during known representative loads and water vapor removal capacity under conditions of very high load are examples of “practical” OQ data. Emissivity data of shelf surface, chamber wall or front door are important to evaluate heat flux to the product (heat transfer of radiation). Such data are easily obtained by performing sublimation tests with pure water in plastic lined bands at predefined chamber pressure and shelf temperature settings. In addition, vial heat transfer coefficients must be determined for a given container system (usually a serum tubing vial). Finally, calculated “loads” with pure excipients may clearly show restrictions for scale-up from a laboratory to a production scale unit.
Our actual work includes:
- process optimization,
- robustness testing (“Design Space”) protocols,
- operational qualification (OQ),
- representative determination of vial heat transfer coefficients,
- scale-up strategies.
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