Importance Of Terminal sterilization In Pharmaceutical Industries

Terminal sterilization is the process of sterilizing a product in its final container. It is an important process as it ensures the product remains sterile.

All medical, ophthalmic and parenteral equipment are sterilized in batches, and usually sterilized using heat. The products themselves however are not thermally sterilized as the heat may damage it. Alternative methods are therefore used, such as filtration which also reduces the risk of a product becoming contaminated.

Before the sterilization process is started, the holding period must be established, which is the time the products must be held at the required temperature or exposed to other sterilization methods to ensure the microbial growth is killed effectively. Any microbial growth that occurs while the products are in storage can affect the quality of the product and must therefore be prevented. 

Methods of Terminal Sterilization:

• Ethylene Oxide: for prefilled syringes and medical devices unable to tolerate high temperatures
• Irradiation: also for prefilled syringes and medical devices unable to tolerate high temperatures
• Moist Heat Sterilization: for large and small parenteral devices and ophthalmic products

During moist heat sterilization, hot water is sprayed inside the sterilizer, and the products to be sterilized are then placed inside. Steam is not used as the temperature is too high and may cause the drug to degrade. The temperature required varies depending on how sensitive the product is to heat, and no set combination of time and heat can be used for all products. It is important to reach the F0 value, which is a measure of the effectiveness of sterilization. This can be ensured by increasing the time while reducing the temperature, allowing effective sterilization at a lower temperature when a product is unable to tolerate a high temperature.

To allow effective and uniform sterilization, the products must be loaded into the sterilization chamber in a careful and ordered manner, allowing the heat to circulate around the chamber and access all areas of the products.

Note: before terminal sterilization, effects of terminal sterilization on the product’s integrity must be known, as the heat may degrade the product. The right combination of heat and time must therefore be selected for each product. 

Any of the methods mentioned above, the ethylene oxide, irradiation or moist heat sterilization, can be used for terminal sterilization, however the right form is required depending on the product being used. Validation is also very important as part of the manufacturing process, as it ensures the product has been manufactured according to high standards.