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The Freeze-Drying of Pharmaceuticals in Vials Nested in a Rack System-Part II: Primary Drying Behaviour.
Fiora Artusio1, Marco Adami2, Antonello A Barresi1
1Department of Applied Science and Technology, Politecnico di Torino, 24 Corso Duca degli Abruzzi, 10129 Torino, Italy.
Pharmaceutics
|November 25, 2023
Summary
Freeze-drying biopharmaceuticals involves optimizing vial loading for efficient primary drying. A rack system improves heat transfer uniformity, reducing variability during freeze-drying, crucial for therapeutic stability.
Area of Science:
- Pharmaceutical Sciences
- Chemical Engineering
- Biotechnology
Background:
- Freeze-drying (lyophilization) is essential for biopharmaceutical stability and distribution.
- Primary drying is energy-intensive and dictates overall process time.
- Vial loading configuration significantly impacts freezing and drying stages.
Purpose of the Study:
- To compare the thermal behavior of vials during primary drying in two loading configurations: direct shelf contact versus rack system.
- To evaluate the impact of chamber pressure, shelf temperature, and vial position on heat transfer efficiency.
- To assess the influence of loading configuration on inter-vial temperature uniformity.
Main Methods:
- Investigated overall heat transfer coefficient (U) in freeze-drying.
- Compared direct contact vs. nested vial configurations in a rack system.
- Varied chamber pressures (5-30 Pa) and shelf temperatures (-10°C to +30°C).
- Analyzed thermal behavior across different vial positions (central, semi-border, border).
- Utilized thermal imaging for temperature difference analysis.
Main Results:
- Heat transfer coefficient was less pressure-dependent for nested vials due to their suspended configuration.
- Both configurations showed similar heat transfer efficiency below 10 Pa.
- At higher pressures (>10 Pa), direct contact vials had higher heat transfer coefficients than nested vials.
- The rack system significantly reduced inter-vial variability, enhancing uniformity for central vials.
- Thermal imaging confirmed minimal temperature differences between vials and the rack system.
Conclusions:
- Rack systems offer improved thermal uniformity during primary drying, crucial for consistent biopharmaceutical freeze-drying.
- Loading configuration choice impacts heat transfer efficiency, particularly at higher chamber pressures.
- Rack systems mitigate pressure-related heat transfer variations, leading to more predictable lyophilization outcomes.
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