Differences between Lyophilization and Freeze Drying?
➡️ Lyophilization and freeze drying are terms that are used interchangeably depending on the industry and location where the drying is taking place.
➡️ Hence, we use the term Lyophilization in this article.
What is Lyophilization?
➡️ It is a drying process that allows to preserve the original structure and characteristics of a drug product which is sensitive to heat.
➡️ The process of lyophilization was discovered in 1906 by the Frenchmen Arsène d'ARSONVAL and F. BORDAS, researcher of the Collège de France.
How to work Lyophilization?
➡️ The fundamental principle in lyophilization is sublimation, the shift from a solid directly into a gas. Just like evaporation of liquid to gas, sublimation occurs when a molecule gains enough energy to break free from the molecules around it. Water will sublime from a solid (ice) to a gas (vapor) when the molecules have enough energy to break free but the conditions aren't right for a liquid to form.
➡️ Specific temperature and atmospheric pressure are two major factors that determine phase (i.e. solid, liquid or gas). Any substance can exist in it’s particular phase at certain range of temperature and pressure. If it’s going beyond this range then it’s convert to other phase.
➡️ Product is change it’s current phase (liquid to solid then gas) during lyophilization cycle when applying specific temperature and pressure as per following image.
Objective of Lyophilization:
- To extend shelf life or stability.
- To dry thermolabile substance or products.
- To reduce product weight to lower the transportation cost.
- To eliminate the need of refrigerator storage.
Which drug product can be lyophilized?
➡️ It is an excellent method for preserving a wide variety of heat-sensitive materials such as proteins, microbes, pharmaceuticals, tissues & plasma.
Lyophilization process at pharmaceutical industry:
➡️ In pharmaceuticals industry, lyophilization process must working as per defined cycle path.
➡️ Initially CIP, SIP, vent filter integrity, lyophilizer leak test are prerequisite to start product lyophilization activity.
➡️ After getting satisfactory results from above sequential cycles, product lyophilization activity start.
➡️ Following image is for pharmaceutical industrial operating cycles of lyophilization to getting continuous lyophilized product with it’s original product characteristics.
The 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 0.2 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.
Three main lyophilization stage.
➡️ The lyophilization process consists of three separate, unique, and interdependent processes i.e. freezing, primary drying (sublimation), and secondary drying (desorption).
1. Freezing:
➡️ Freezing can be done in a freezer, a chilled bath (shell freezer) or on a shelf in the freeze dryer.
➡️ Cooling the material below its triple point ensures that sublimation, rather than melting, will occur. This preserves its physical form. Low temperature and low pressure are maintained.
The rate of ice crystallization defined freezing process and efficiency of primary drying.
2. Primary Drying (Sublimation):
➡️ It has been longest phase of lyophilization cycles, in which the pressure is lowered and heat is added to the material in order for the water to sublimate.
➡️ Heat is introduced from shelf to the drug product by circulation of silicone oil. The vacuum speeds sublimation.
➡️ The cold condenser provides a surface for the water vapor to adhere and solidify. The condenser also protects the vacuum pump from the water vapor.
➡️ About 95% of the water in the material is removed in this phase. Primary drying can be a slow process.
➡️ Too much heat can alter the structure of the material if it is not validate properly.
3. Secondary Drying (Desorption):
➡️ During this phase, ionically-bound water molecules are removed. By raising the temperature higher than in the primary drying phase, the bonds are broken between the material and the water molecules.
➡️ Freeze dried materials retain a porous structure. After the lyophilization process is complete, the vacuum can be broken with an inert gas i.e. Nitrogen before the material is sealed.
➡️ Most materials can be dried to 1-5% residual moisture.
Advantages of lyophilization:
- Ease of processing a liquid, which simplifies aseptic handling
- Enhanced stability of a dry powder
- Removal of water without excessive heating of the product
- Enhanced product stability in a dry state
- Rapid and easy dissolution of reconstituted product
Disadvantages of lyophilization:
- Increased handling and processing time
- Need for sterile diluent upon reconstitution
- Cost and complexity of equipment
About the Author:
Dhansukh Viradiya is a highly accomplished expert in the pharmaceutical and biopharmaceutical industries. With over 10 years of experience in the field, he has gained comprehensive knowledge and expertise in various areas, including Process Validation, Cleaning Validation, Quality Management System, In-process quality assurance, Qualification etc.
Mr. Dhansukh holds a Master's degree in Pharmacy from a renowned University, where he specialized in Quality Assurance.
As a thought leader, Mr. Dhansukh has published numerous articles and white papers on various topics related to pharmaceutical and biopharmaceutical industries. His research work focuses on emerging trends, current regulatory expectations, advancements in technology, personalized medicine, and the intersection of healthcare and technology.
With his passion for improving patient care and dedication to advancing the field, Dhansukh Viradiya continues to make significant contributions to the pharmaceutical and biopharmaceutical industries. His insights and expertise make him a valuable resource in understanding the dynamic landscape of these sectors and their impact on global healthcare.
Disclaimer: The author's biography is provided for informational purposes only and does not imply any endorsement or affiliation with the article or its content.
Very informative
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