Freeze drying pharmaceuticals uses a process called lyophilization to lower the temperature of the product to below freezing, and then a high-pressure vacuum is applied to extract the water in the form of vapour. The vapour collects on a condenser, turns back to ice and is removed.
Dehydration process,
Typically used to preserve a perishable material or make the material more convenient for transport,
Mostly used for light food required by astronauts, hikers
introduction, theory of drying, applications of drying, construction & working about fluidised bed dryer,use of tray dryer,construction about vacuum dryer, construction & working about drum dryer, construction about spray dryer
Pharmaceutical Dryers. Dryers are used in a variety of industries, such as the food processing, pharmaceutical, paper, pollution control and agricultural sectors. ... Direct dryers convectively heat a product through direct contact with heated air, gas or a combusted gas product.
spray drying is technology widely used in milk powder and coffee powder manufacturing industry because of its working principle and technology involved..
Freeze drying pharmaceuticals uses a process called lyophilization to lower the temperature of the product to below freezing, and then a high-pressure vacuum is applied to extract the water in the form of vapour. The vapour collects on a condenser, turns back to ice and is removed.
Dehydration process,
Typically used to preserve a perishable material or make the material more convenient for transport,
Mostly used for light food required by astronauts, hikers
introduction, theory of drying, applications of drying, construction & working about fluidised bed dryer,use of tray dryer,construction about vacuum dryer, construction & working about drum dryer, construction about spray dryer
Pharmaceutical Dryers. Dryers are used in a variety of industries, such as the food processing, pharmaceutical, paper, pollution control and agricultural sectors. ... Direct dryers convectively heat a product through direct contact with heated air, gas or a combusted gas product.
spray drying is technology widely used in milk powder and coffee powder manufacturing industry because of its working principle and technology involved..
Freeze Drying merupakan metoda pengawetan produk pangan agar dihasilkan produk yang memiliki stabilitas pada strukturnya baik secara kimiawi ataupun biologi. Sistem yang terdapat dalam Freeze Dryer (alat/mesin Freeze Drying) pun tentu sangat kompleks. Saat ini banyak industri yang menggunakan metoda ini, tidak hanya bahan pangan, tetapi juga bisa untuk bidang farmasi dan boiteknologi, dekorasi, makanan astronout, penyimpanan dokumen, dll.
Founded in 1988, Pyramid Laboratories, Inc., is a contract parenteral drug manufacturer and analytical provider that serves both the pharmaceutical and biotechnology industries. Among the Pyramid Laboratories, Inc., offerings is its equipment, including a laboratory-scale lyophilizer as well as a differential scanning calorimeter, along with a team of scientists to optimize the formulation of the product for lyophilization, also known as freeze-drying.
Definition of drying
Importance of drying
Difference between drying and evaporation
Equipments
References
Definition
A stabilizing process in which a substance is first frozen and then the quantity of the solvent is reduced, first by sublimation (primary drying stage) and then desorption (secondary drying stage) to values that will no longer support biological activity or chemical reactions.
History
Freeze drying was first actively developed during WORLD WAR II transport of serum.
The main aim was to store the products without refrigeration and to remove moisture from thermolabile compounds.
Atlas in 1961 built 6 production freeze drying cabinet for Nestle group in Germany, Holland.
Principle
Lyophilization is carried out using a simple principle of physics sublimation. Sublimation is the transition of a substance from the solid to the vapour state, without first passing through an intermediate liquid phase.
Lyophilization is performed at temperature and pressure conditions below the triple point, to enable sublimation of ice.
The entire process is performed at low temperature and pressure by applying vacuum, hence is suited for drying of thermolabile compounds.
The concentration gradient of water vapour between the drying front and condenser is the driving force for removal of water during lyophilization.
The process of freeze drying with greater emphasis on the uses in the fisheries food processing sector. The presentation shows the process involved and the different steps involved and the effect of the process on the food material.
Freezing is a unit operation in which temperature of a food is reduced below its freezing point (removal of sensible & latent heat of fusion), and a proportion of the water undergoes a change in state to form ice-crystals. Immobilization of water to ice and the resulting concentration of
dissolved solutes in unfrozen water lowers the water activity of the food. Lowering of temperature, lowers the microbial activity as well as suppresses the chemical reactions in the food. Generally,
we find two type of freezing method, quick freezing and slow freezing. In slow freezing, food products are introduced to low temperature for relatively longer time duration and hence the ice crystal formed are of larger in size, which are sometimes not at all desirable depending on
characteristic of food product. In quick freezing, relatively even lower temperature is used for food product but exposure time is less. Hence the ice crystal formed are of smaller size. Even though small ice crystal formed during quick freezing helps in preserving the texture and other characteristic of product, sometimes it may cause to temperature shock to product. Choosing the method of freezing is hence of utmost importance.
Lyophilization or freeze drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. The process consists of three separate, unique, and interdependent processes; freezing, primary drying (sublimation), and secondary drying (desorption).
The advantages of lyophilization include:
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 include:
Increased handling and processing time
Need for sterile diluent upon reconstitution
Cost and complexity of equipment
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 0.22 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.
There are many new parenteral products, including anti-infectives, biotechnology derived products, and in-vitro diagnostics which are manufactured as lyophilized products. Additionally, inspections have disclosed potency, sterility and stability problems associated with the manufacture and control of lyophilized products. In order to provide guidance and information to investigators, some industry procedures and deficiencies associated with lyophilized products are identified in this Inspection Guide.
It is recognized that there is complex technology associated with the manufacture and control of a lyophilized pharmaceutical dosage form. Some of the important aspects of these operations include: the formulation of solutions; filling of vials and validation of the filling operation; sterilization and engineering aspects of the lyophilizer; scale-up and validation of the lyophilization cycle; and testing of the end product. This discussion will address some of the problems associated with the manufacture and control of a lyophilized dosage form.
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2. INTRODUCTION
Lyophilization or freeze drying is a process in which water is frozen,
followed by its removal from the sample, initially by sublimation
(primary drying) and then by desorption (secondary drying).
Freeze- drying is a process of drying in which water is sublimed from
the product after it is frozen.
It is a drying process applicable to manufacture of certain
pharmaceuticals and biologicals that are thermolabile or otherwise
unstable in aqueous solutions for prolonged storage periods, but
that are stable in the dry state.
The term “lyophilization” describes a process to produce a product
that “loves the dry state”.
3. PRINCIPLE
The main principle involved in freeze drying is a phenomenon called
sublimation, where water passes directly from solid state (ice) to the
vapor state without passing through the liquid state.
The material to be dried is first frozen and then subjected under a
high vacuum to heat (by conduction or radiation or by both) so that
frozen liquid sublimes leaving only solid ,dried components of the
original liquid.
4. Rate of drying of water
To extract water from foods, the process of lyophilization consists of :
1. Freezing the food so that the water in the food become ice.
2. Under a vacuum, sublimating the ice directly into water vapour.
3. Drawing off the water vapour.
4. Once the ice is sublimated, the foods are freeze- dried and can be
removed from the machine.
5. The fundamental process steps
1. Freezing:
The product is frozen.
This provides a necessary condition for low temperature drying.
2. Vacuum:
After freezing, the product is placed under vacuum. This enables the frozen solvent in
the product to vaporize without passing through the liquid phase, a process known as
sublimation.
3. Heat:
Heat is applied to frozen product to accelerate sublimation.
4. Condensation:
Low temperature condenser plates remove the vaporized solvent from the vacuum
chamber by converting it back to a solid. This completes the separation process.
Resulting product has a very large surface area thus promoting rapid dissolution of
dried product.
6. TRADITIONAL LYOPHILIZATION
TECHNOLOGY
For nearly 30 years, lyophilization has been used to stabilize many
types of chemical components. In their
liquid form,
biochemicals and unstable chemical reagents,
temperature sensitive,
chemically reactive with one another.
Lyophilization gives unstable chemical solutions a long shelf life
when they are stored at room temperature.
The process gives product excellent solubility characteristics,
allowing for rapid reconstitution.
Heat- and moisture-sensitive compounds retain their viability.
7. PROCESSING
Freeze-drying process
Freeze drying is mainly used to remove the water from sensitive
products, mostly of biological origin, without damaging them, so they
can be preserved easily, in a permanently storable state and be
reconstituted simply by adding water.
Examples of freeze dried products are: antibiotics, bacteria, sera,
vaccines, diagnostic medications, protein- containing and
biotechnological products, cells and tissues, and chemicals.
The product to be dried is frozen under atmospheric pressure.
Then, in an initial drying phase referred to as primary drying, the water
(in form of ice) is removed by sublimation
In the second phase, called secondary drying, it is removed by
desorption. Freeze drying is carried out under vacuum.
8. 1. Pretreatment
Pretreatment includes any method of treating the product prior to freezing.
This may include concentrating the product, formulation revision (i.e., addition of
components to increase stability and/or improve processing), decreasing a high
vapor pressure solvent or increasing the surface area.
Methods of pretreatment include:
Freeze concentration,
Solution phase concentration,
Formulation to Preserve Product Appearance,
Formulation to Stabilize Reactive Products,
Formulation to Increase the Surface Area, and
Decreasing High Vapor Pressure Solvents
9. THE FREEZE-DRYING CYCLE:
Lyophilization is the most common method for manufacturing solid
pharmaceutical products and is central to the preservation of materials
which must be dried thoroughly in order to ensure stability.
To meet this requirement, a solution’s lyophilization occurs in three steps:
(1) freezing to convert most of the water into ice,
(2) primary drying to sublime the ice, and
(3) secondary drying to remove unfrozen water by desorption.
To technically realize this manufacturing process, a freeze dryer is
commonly constructed with two main parts:
“drying chamber” holding temperature controlled shelves is connected by a
valve to a “condenser chamber”, which contains coils capable to achieve
very low temperatures between -50°C and -80°C.
10. The freeze- drying process consists
of three stages.
1) Freezing
2) Primary drying
3) Secondary drying
11. 2. Freezing
The product must be frozen to a low enough temperature to be
completely solidify.
Since freeze drying is a change in state from the solid phase to the
gaseous phase, material to be freeze-dried must first be adequately
pre-frozen.
The method of prefreezing and the final temperature of the frozen
product can affect the ability to successfully freeze dry the material.
Rapid cooling results in small ice crystals, useful in preserving
structures to be examined microscopically, but resulting in a product
that is, more difficult to freeze dry.
Slower cooling results in large ice crystals and less restrictive channel
in the matrix during the drying process.
12. Cont…
Products freeze in two ways, the majority of products that are
subjected to freeze-drying consists primarily of water.
Most samples that are to be freeze dried are eutectics, which are
mixtures of substances that freeze at lower temperature than the
surrounding water.
It is very important in freeze-drying to pre freeze the product to
below the eutectic temperature before beginning the freeze-drying
process.
The second type of frozen product is a suspension that undergoes
glass formation during the freezing process.
13. Primary drying
After prefreezing the product, conditions must be established in
which ice can be removed from the frozen product via sublimation,
resulting in a dry, structurally intact product.
This requires very carefully control of the two parameters.
1. Temperature and
2. Pressure involved in freeze-drying system.
The rate of sublimation of ice from a frozen product depends upon
the difference in vapor pressure of the product compared to the
vapor pressure of the ice collector.
14. Cont…
Molecules migrate from the high- pressure sample to a lower
pressure area. Since vapor pressure is related to temperature, it is
necessary that the product temperature is warmer than the cold
trap (ice collector) temperature.
Temperature at which a product is freeze dried is balanced
between the temperature that maintains the frozen integrity of the
product and the temperature that maximizes the vapor pressure of
the product.
This balance is key to optimum drying.
15. Cont…
Heat enters the products by one of several mechanisms: -
1. By direct contact between the container base and the shelf, so here
the shape of the container is important.
2. By conduction across the container base and then through the frozen
mass to the drying front (also called the sublimation interface)
3. By gaseous convection between the product and residual gas
molecules in the chamber.
4. By radiation, this is low due to low temperature encountered in freeze-drying.
Convection is certainly the most important of these mechanisms
16. Secondary drying
After primary freeze-drying is complete, and all ice has sublimed, bound
moisture is still present in the product.
The product appears dry, but the residual moisture content may be as
high as 7-8% continued drying is necessary at warmer temperature to
reduce the residual moisture content to optimum values.
This process is called ‘Isothermal Desorption’ as the bound water is
desorbed from the product.
Secondary drying is normally continued at a product temperature
higher than ambient but compatible with the sensitivity of the product.
In contrast to processing conditions for primary drying which use low
shelf temperature and a moderate vacuum, desorption drying is
facilitated by raising shelf temperature and reducing chamber pressure
to a minimum.
17. Cont…
Care should be exercised in raising shelf temperature too highly;
since, protein polymerization or biodegradation may result from
using high processing temperature during secondary drying.
Secondary drying is usually carried out for approximately 1/3 or 1/2
the time required for primary drying.
The general practice in freeze-drying is to increase the shelf
temperature during secondary drying and to decrease chamber
pressure to the lowest attainable level.
18. FREEZE DRYER DESIGN
Essential Components
Chamber
This is the vacuum tight box, sometimes called the lyophilization chamber or cabinet.
The chamber contains shelf or shelves for processing product.
The chamber can also fit with a stoppering system.
It is typically made of stainless steel and usually highly polished on the inside and
insulated and clad on the outside.
The door locking arrangement by a hydraulic or electric motor.
Shelves
The shelf act as a heat exchanger, removing energy from the product during freezing,
and supplying energy to the product during the primary and secondary drying
segments of the freeze drying cycle.
The shelves will be connected to the silicone oil system through either fixed or flexible
hoses. Shelves can be manufactured in sizes up to 4 m² in area.
19. Cont…
Process Condenser
The process condenser is sometimes referred as just the condenser or the cold trap.
It is designed to trap the solvent, which is usually water, during the drying process.
The process condenser will consist of coils or sometimes plates which are refrigerated
to allow temperature.
These refrigerated coils or plates may be in a vessel separate to the chamber, or they
could be located within the same chamber as the shelves.
Hence there is designation “external condenser” and “internal condenser”. Physically,
the external condenser is traditionally placed behind the chamber, but it may be at
the side, below or above.
The position of the condenser does not affect trapping performance. For an internal
condenser the refrigerated coils or plates are placed beneath the shelves on smaller
machines, and behind the shelves on larger machines, but again there is no
performance constraint, only the geometry of the chamber.
20. Cont…
Shelf fluid system
The freeze-drying process requires that the product is first frozen and
then energy in the form of heat is applied throughout the drying phases
of the cycle.
This energy exchange is traditionally done by circulating a fluid through
the shelves at a desired temperature.
The temperature is set in an external heat exchange system consisting
of cooling heat exchangers and an electrical heater.
The fluid circulated is normally silicone oil.
This will be pumped around the circuit at a low pressure in a sealed
circuit by means of a pump.
21. Cont…
Refrigeration system
The product to be freeze dried is either frozen before into the dryer or
frozen whilst on the shelves.
Compressors or sometimes-liquid nitrogen supplies the cooling energy.
Most often multiply compressors are needed and the compressor may
perform two duties, one to cool the shelves and the second to cool the
process condenser.
22. Cont…
Vacuum system
To remove solvent in a reasonable time, vacuum must be applied during the
drying process.
The vacuum level required will be typically in the range of 50 to 100μ bar.
To achieve such a low vacuum, a two stage rotary vacuum pump is used.
For large chambers, multiple pumps may be used.
Control system
Control may be entirely or usually fully automatic for production machines.
The control elements required are as mentioned above, shelf temperature,
pressure and time.
A control program will set up these values as required by the product or the
process. The time may vary from a few hours to several days.
24. FREEZE DRYING METHODS
1. Manifold method
In the manifold method, flasks ampoules or vials are individually
attached to the ports of a drying chamber.
The product either frozen in a freezer, by direct submersion in a low
temperature bath, or by shell freezing, depending on the nature of the
product and the volume to be freeze dried.
The prefrozen product is quickly attached to the drying chamber or
manifold to prevent warming.
The vacuum must be created in the product container quickly, and the
operator relies on evaporative cooling to maintain the low temperature
of the product.
This procedure can only be used for relatively small volumes and
product with high eutectic and collapse temperatures.
25. • Manifold drying has several
advantages over batch tray drying.
• Since the vessels are attached to the
manifold individually, each vial or flask
has a direct path to the collector.
• This removes some of the competition
for molecular space created in a
batch system, and is most ideally
realized in a cylindrical drying
chamber where the distance from the
collector to each product vessel is the
same.
26. 2. Batch method
In a batch drying, large numbers of similar sized vessels containing
like product are placed together in a tray dryer.
The product is usually prefrozen on the shelf of the tray dryer.
Precise control of the product temperature and the amount of heat
applied to the product during drying can be maintained.
Slight difference in heat input from the shelf can be expressed in
different areas.
Batch drying is used to prepare large numbers of ampoules or vials
of one product and is commonly used in the pharmaceutical
industry.
27.
28. 3. Bulk method
Bulk drying is generally carried out in a tray dryer like batch drying.
However, the product is poured into a bulk pan and dried as a
single unit.
Although the product is spread through out the entire surface area
of the shelf and may be the same thickness as product in vials, the
lack of empty spaces within the product mass changes the rate of
heat input.
The heat input is limited primarily to that provided by contact with
the shelf.
29. APPLICATIONS
Pharmaceutical and biotechnology
1. Pharmaceutical companies often use freeze-drying to increase the shelf life of
products, such as vaccines and other injectables.
2. 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.
Food Industry
1. Freeze-drying is used to preserve food and make it very lightweight.
2. The process has been popularized in the forms of freeze-dried ice cream, an
example of astronaut food.
Technological Industry
1. In chemical synthesis, products are often freeze- dried to make them more stable, or
easier to dissolve in water for subsequent use.
2. In bio- separations, freeze-drying can be used also as a late-stage purification
procedure, because it can effectively remove solvents.
30. The advantages of Lyophilization
• Chemical decomposition is minimized.
• Removal of water without excessive heating.
• Enhanced product stability in a dry state.
• Ease of processing a liquid, simplifies aseptic handling.
• More compatible with sterile operations than dry powder filling.
31. Disadvantages of Lyophilization
• Increased handling and processing time.
• Volatile compounds may be removed by vacuum.
• Need for sterile diluents upon reconstitution.
32.
33. REFERENCES
1. Akers MJ, Fites AL, Robinson RL. Types of parenteral administration. Journal of
parenteral science and Technology, 1987, 41, 88-95.
2. Lippincolt, Williams K. Remington, The Science & practice of pharmacy,
Parenteral Preparation, 20th ed, ISE publication, Phelabelphia. 2000, 1, 804-819.
3. Rambhatla S, Pikal MJ. Heat and mass transfer scale-up issues during
freezedrying, I: atypical radiation and the edge vial effect. AAPS PharmSciTech,
2003, 4(2), 111–120.
4. Pikal MJ, Roy ML, Shah S. Importance of freeze-dried pharmaceuticals: role of
the vial. J Pharm Sci, 1984, 73(9), 1224–1237