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Lyophilization and Applications in Pharmaceutics
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3. • Definition:
Freeze drying is the removal of ice or other
frozen solvents from a material through the
process of sublimation and the removal of
bound water molecules through the process
of desorption.
The name lyophilization is derived from the
Greek for ‘to make solvent-loving’.
4. • Lyophilization and freeze drying are terms that
are used interchangeably.
• Controlled freeze drying keeps the product
temperature low enough to avoid changes in the
dried product appearance and characteristics.
• Excellent method for preserving a wide variety of
heat-sensitive materials such as:
– Proteins
– Microbes
– Pharmaceuticals
– Tissues & plasma.
5.
6. Objectives of lyophilization process:
• To preserve the biological activity of a product.
• To reduce the product weight to lower the
transportation cost.
• To extend the shelf life or stability.
• To dry thermolabile materials.
• To eliminate the need for refrigerated storage.
• To get accurate, sterile dosing into the final
product container.
7. Instrument used for lyophilization:
The instrument used for lyophilization is called
lyophilizer or freeze-dryer.
8. Steps for lyophilization
• Pretreatment of Formulation
• Loading of Container (Bulk, Flask, Vials)
• Freezing (Thermal Treatment)of formulation at
atmospheric pressure
• Primary Drying (Sublimation) under vacuum
• Secondary Drying (Desorption) under vacuum
• Backfill & Stoppering (for product in vials) under
partial vacuum
• Removal of Dried Product from Freeze Dryer
9. • freeze-drying should yield a product that has a
short reconstitution time with acceptable
potency levels.
• Potency is the concentration (EC50) or dose
(ED50) of a drug required to produce 50% of
that drug’s maximal effect.
• The process of adding a diluent to a dry
ingredient to make it a liquid, is called
reconstitution.
10. • Conditions for lyophilization:
The pressure inside the freeze dryer must be
below the “triple point value” for the product
The temperature of the sample is maintained
below its freeze point in the lyophilization
process.
12. • Pre-freezing
The sample is frozen, which means the water
in the product is converted to ice, thereby the
phase has changed from liquid to solid. Slow
pre-freezing will produce lager ice crystals,
which are easier to lyophilize, whilst fast pre-
freezing results in smaller crystals.
13. • Primary drying
Sublimation starts
Ice is sublimized into vapours
vapors are collected at condenser (here, vapours
are again fused into ice)
Energy is provided by gently-heating the sample.
Avoid excess heating (in this case, condenser
unable to condense vapors with escalating risk of
sample melting)
14. • Secondary drying
Removal of tightly bound water molecules
This water has high vapor pressure than that of
water in its free form due to strong bonding with
sample
Higher temperature and low pressure is applied,
but keeping in view the fact that any biological
activity must not be impaired
This process is Desorption