Aseptic Filtration
The formulation (solution) is passed through a sterile 0.22 μm membrane filter, removing bacteria and other particulates.
The filtered solution is then filled into previously sterilized containers under laminar airflow conditions.
Terminal Sterilization
If the formulation and container can withstand heat, autoclaving at 121°C for 15–20 minutes is often employed.
Advantages: higher sterility assurance level.
Disadvantages: not suitable for heat-labile drugs.
Dry Heat Sterilization (for Ointments)
The base can be sterilized by heating in an oven at 160–170°C for a specific time.
Drug powders might be sterilized separately if stable to heat, then mixed under aseptic conditions.
Gamma Irradiation or Ethylene Oxide
Used in specialized cases (e.g., certain packaging materials).
Less common for routine ophthalmic solutions due to potential effects on drug stability and safety.