NEWSLETTER
ISSUE
Jan to Mar, 2020 Volume 11
Importance of Sterilization and Various cycles in Pharmaceutical manufacturing
Sterilization is one of the critical processes in the sterile manufacturing facility, so, understanding its significance is imperative. During the manufacturing process, several materials move from one processing area to another or from one class/grade room to another class/grade room, i.e. class B to class C or class B to class A or vice a versa. During this movement, the sterilization step is employed to ensure sterility of the area, where the material is being transferred.
There are different types and shapes of material that goes through the sterilization process, such as garments (gowns), tools, product in open container, product in a closed container, product in its final container (in glass bottles, plastic bottles, vials, syringes etc.). These materials are generally termed as “Load” in the industry. These various loads have a unique material characteristic, and it may get affected by the application of temperature and pressure during sterilization. Therefore, separate sterilization method (cycle) is required to suit the material characteristic of the load.
Therefore, It is essential to understand the basics of the sterilization process and cycles in details.
What is Sterilization?
Sterilization is a process designed to remove or destroy all viable forms of microbial life, including bacterial spores, to achieve an acceptable sterility assurance level. Generally, Sterility Assurance Level (SAL) of 6 log reduction is attained.
Types of Sterilization
Sterilization is classified into two primary groups, Cold sterilization and Hot sterilization.
Hot sterilization is commonly used in Pharmaceutical processing.
Hot sterilization is further classified into Dry heat sterilization and Moist heat sterilization. These different types of sterilization are employed for different kinds of loads and application need.
For example, the Moist Heat sterilization is used for loads like glassware, unwrapped goods, waste, utensils etc. Similarly, Steam-air mixture sterilization is used for product in a hermetically sealed container, and the load is desired dry post sterilization. On the other hand, water air mixture, also known as Super-heated water spray sterilizer, is used for sterilization of product in a sealed container, usually HDPE/LDPE, PVC multilayer, plastic bags, which tends to deform with direct contact of steam.
There are several commonly used operating cycles as listed below.
- Gravity Cycle
- Vacuum Cycle
- Liquid Cycle
- Flash Cycle
- F0 Cycle
- Air-Over Pressure Cycle
- Steam-Air Mix Cycle
- Super-Heated Water Spray Cycle
- Rapid Cooling Cycle
- Bowie-Dick Test Cycle
- Vacuum Leak Test Cycle
Gravity Cycle
Gravity cycle is the most basic cycle used in Steam Sterilizer. As the name indicates, the steam displaces air by gravity in the sterilizer chamber through drain port without any mechanical assistance. Gravity cycle is used for sterilization of material such as glassware, utensils, unwrapped goods, red bag etc. The challenge with gravity cycle is that at the end of the cycle, the load can be wet and hot. This cycle may not be suitable for the application where the load is desired dry and cold at the end of the sterilization cycle
The cycle consists of three primary phases,
- Purge
- Sterilization
- Exhaust
Vacuum Cycle (HPHV)
Vacuum cycle is also known as HPHV (High-Pressure High Vacuum) Cycle. In the vacuum cycle, the air is mechanically removed from the chamber by a series of vacuum & pressure pulses. These pulses ensure complete removal of air from the chamber. Air removal is critical in achieving sterilization of the load as the minute presence of air can resist steam penetration within the load and may end up in sterilization failure. Vacuum cycle is used for effective sterilization ofporous loads such as Garments, Beddings, wrapped goods and even used for animal cases, red bags and other porous material.
Vacuum cycle helps in instantaneous steam penetration into the load and reduces sterilization cycle time in addition to achieving reliable sterilization.
Vacuum cycle consists of the following phases
Air removal phase: During this phase, a series of alternating steam pressure injection and vacuum pulses are applied. This pulse ensures complete removal of air from the chamber and effective steam penetration within the load before attaining sterilization temperature and pressure.
Heating phase: During the heating phase, like gravity cycle, the chamber attains sterilization temperature and pressure.
Sterilization phase: On attaining sterilization temperature, the sterilizer holds (maintains) the temperature and pressure of the chamber till predefined time. Usually, it is 121°C for 20 minutes for steam sterilization like gravity cycle.
Cooling phase: During Cooling phase, the chamber pressure and temperature gradually decrease to cool down the load within the chamber before unloading.
Exhaust phase: During the exhaust phase, vacuum pulses can be employed to enhance the drying process for the load quickly.
More sterilization cycle to continue in next newsletters.
